Research ArticleDevelopment of Epoxy Based Surface Tolerant CoatingImprovised with Zn Dust and MIO on Steel Surfaces

Rachna Jain1 Manish Wasnik2 Amit Sharma3 Manish Kr Bhadu1

T K Rout1 and A S Khanna2

1 TATA Steel Ltd Jamshedpur India2 IIT Bombay India3 Stanvac-Superon Group Gurgaon India

Correspondence should be addressed to Rachna Jain rchnjaingmailcom

Received 16 November 2013 Revised 28 January 2014 Accepted 18 February 2014 Published 3 April 2014

Academic Editor Fahmina Zafar

Copyright copy 2014 Rachna Jain et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Couple of high strength and flexible surface tolerant coatings were designed for oil contaminated rusty and minimally preparedsteel surfaces These coatings are to have strong interfacial adhesion due to low surface tension and sustain more than 5MPa pullout force consistently The effect of optimized concentration of zinc dust and micaceous iron oxide (MIO) as pigments is evaluatedfor these surface tolerant coating systems It has been noticed that the presence of these two ingredients has enhanced corrosionresistancemore than several times as compared to commercially available coating systemsThe corrosion simulation test in 35 wtNaCl has evident for significant improvement in terms of delaying blistering and delamination The high pore resistance (119877119901)indicates the slowmigration of ions andwater into the substrate and coating interface which could be the reason of the improvementin corrosion process

1 Introduction

Surface tolerant coatings are the coatings which can beapplied over moist chemically contaminated or rusty steelold painted surface and other minimally prepared surfacesMost commonly used are red lead alkyd epoxy mastic alu-minum epoxymastic moisture-cured urethane coal tarmas-tic modifiedwax and grease basedmaterialsThe addition ofzinc and micaceous iron oxide (MIO) in the binder providethe cathodic and barrier protection with an excellent surfacetolerant tendency The coating properties of a ldquofairrdquo surfacetolerant coating are excellent penetration wettability adher-ence ability under dry and wet conditions high electricalresistance to provide a barrier between anodic and cathodicsites of corrosion cells excellent barrier properties such asimpermeability to water oxygen and ions neutralization ofchloride bromide and sulfate salts and ability to suppressinternal stress Surface tolerant coatings do not require highprofile surface preparation so no generation of fine dustabrasive particulates but abrasive blast cleaning produces

toxic debris and its disposal may be harmful Surface tolerantcoatings can be a replacement of high performance marinecoatings systems (required a high degree of surface clean-liness) No cleanliness of high performance marine coatingsystems may cause the potential degradation of performanceand reduction in durability of high performance corrosioncontrol coating systems [1ndash3]

The surface tolerant coatings are mainly used as main-tenance and anticorrosive property in marine and industrialenvironments The challenge of reducing the level of surfacepreparation without degrading performance also exists inother areas of industrial coatings such as chemical plants Toovercome this apparent disparity between levels of cleanlinessand coating performance many new coating products arebeing formulated to accommodate reduced cleaning levels[4]

Epoxy resin is known for its high range of attainable pro-perties and versatility with excellent surface tolerance ten-dency due to its chemical structure in curing conditionsHigh crosslinking tendency during curing makes the coating

Hindawi Publishing CorporationJournal of CoatingsVolume 2014 Article ID 574028 15 pageshttpdxdoiorg1011552014574028

2 Journal of Coatings

Scratch

Steel

Zinc primer

Top coat

(a)

Active zinc Corrosion productSteel

Scratch

Zinc primer

Top coat

(b)

Inactive zincSteel Corrosion product

Scratch

Zinc primer

Top coat

(c)

Figure 1 Mechanisms of a zinc coating system (a) scribe or scratch is introduced down to the steel surface (b) near scratch zinc becomesactive while zinc-iron corrosion products are being built up (c) zinc becomes inactive but the coating provides only barrier and inhibitiveprotection

tough with excellent surface protection chemical resistantflexible with high strength hard and good heat and electricalresistant [5 6] Other important applications include repair ofcracks andfissures in structural concrete above or underwaterand as adhesives for ceramics Apart from its excellentadhesion the surface tolerant properties also depend onthe pigments additives in the epoxy coating which is alsoresponsible for cathodic as well as barrier protection [7 8]

The viscosity adhesion flexibility impact resistance andsubstrate wetting directly depend on molecular weight ofunreacted epoxy resin while cross-linking density solventresistance and hardness decrease as molecular weight ofunreacted epoxy resin decreases [9] Formation of epoxyresin is the combination of bisphenol A (used for hightemperature and chemical resistance) and epichlorohydrinin presence of alkaline and the resultant is diglycidyl etherof bisphenol A (DGEBA) which is formed after extractingunreacted phenol and acetone [10]

Epoxy resins have the ability to transform readily fromthe liquid state to tough and hard solids This hardening isaccomplished by addition of chemically active reagent knownas curing agent (hardener) Dry time penetration and wet-tability depend upon hardener which cross-linked with resinand provide high chemical resistant with good flexibility Inthis paper cycloaliphatic amines are used as a hardener (roomtemperature curing and convenient handling) because theseamines provide good adhesion as their compatibility with

epoxy and easy availability of lone pairs on nitrogen atom(because of noninvolvement in aromaticity) to zinc and ironsurfaces (chemiadsorption) as compared to aromatic aminesThere is a crosslinking structure formed after curing whichis in between cycloaliphatic amine and epoxy resin due tothe polar bonds interaction of epoxy resin with available lonepairs of nitrogen atom of cycloaliphatic amine [9ndash11]

Many pigments can be used with epoxy resin but wehave chosen zinc pigment because of its lower potential Theperformance of zinc depends on ratio of pigment volumeconcentration (PVC) to critical pigment volume concentra-tion (CPVC) If the ratio is lt1 then it will provide the barrierprotection If the ratio is gt1 then it will provide the cathodicprotection but influences its permeability and mechanicalproperties But the sacrificial action of zinc starts up onlywhen there is uninterrupted contact between metal particlesthat is infiltration path [12] So zinc primers are widely usedin various aggressive atmospheres such as offshore industrialand so forth because of its distinctive property of metalprotection even after the scribe or any mechanical damageto the coating which provides good sacrificial protection atthe early stage and the alkaline nature and low solubilityof corrosion products of zinc provides additional barrierprotection at the later stage as shown in Figure 1 [13]

Type of pigment or filler used in organic coating acts asbarrier and is of crucial importance to the pigment-polymermatrix interaction because undercoat layer increases the free

Journal of Coatings 3

Substrate

UV rays

Pigment particles

Figure 2 The flip-flop effect showing protection against ultraviolet(UV)

mean path for the diffusion of water oxygen and ions Themost common lamellar pigments are MIO flakes of glassmetallic Al particles Zn dust and so forth [14] Zinc withepoxies provides films with moderate porosity Specially for-mulated intermediate andor topcoats are required to over-come blistering over such zinc-based primers (zinc primer isthe zinc dust spherical lamellar or combination of both thatis dispersed in organic epoxies resin) By lowering the zincpigment content in the formulation application blisteringproblem can be solved by scarifying the primerrsquos galvanicproperties Performance of zinc primers also depends on themorphology of the Zn particle smaller and lamellar particlesgive better results than larger and spherical particles [15]

Figure 3 shows the lamellar MIO creating tortuous pathfor water and micaceous iron oxide (MIO) is iron oxidein a form that resembles mica a highly structured layeredmineral The lamellar shape of this micaceous form of ironoxide (high volumetric pigment concentration) offers greatlyenhanced barrier protection due to its tendency to orientparallel to the substrate thereby increase the mean freepath for the diffusion of the aggressive species The lamellarnature and shiny surface appearance of MIO pigments offerultraviolet protection (reflecting barrier to the light) andprotect against blistering and delamination to the underlyingepoxy system This mechanism of protection is known asflip-flop effect as shown in Figure 2 Epoxy and enamelbased coatings normally chalk on exposure to ultraviolet rayshowever in coatings pigmented with MIO only the resin onthe surface of the uppermost MIO particles is exposed toultraviolet rays and will chalk [14]

In this paper solvent borne epoxy mastic as a primerwas synthesized by using bisphenol A based epoxy resinmodifying with zinc dust and MIO It was observed thatMIO and Zinc dust are used in coatings as a barrier andcathodic protection respectively and it improves mechanicaland corrosion properties of coatingsThe emphasis was givento the development of MIO and Zinc dust incorporated intoepoxy based coating So in order to achieve the objectivetwo types of systems (two types of surface tolerant coatingsystems STC1 and STC2 were developed (1) STC1 comprisestwo coat of epoxy mastic primer with zinc dust and (2) STC2

Substrate

Lamellar pigment particles

Water droplets

Substrate

Spherical pigment particles

Water droplets

Figure 3 Lamellar MIO creating tortuous path for water when thewater permeates

comprises two coat of epoxymastic withMIO)were preparedand characterized with optimized concentration of MIO andzinc dust with commercially available coating systems whichare not suitable for application on partially cleaned surfaceprepared according to St2St3 standards The coating wasevaluated for mechanical and corrosion resistance propertiesfor steel as a primer coating

2 Experimental Procedure

21 Materials and Reagents

(1) Epoxy resins unmodified epoxy resin derived frombisphenol A-epoxy equivalent weight (EEW) 185ndash190 Source Aditya birla chemicals (Thailand) LtdThailand

(2) Amine hardener or curing agent (source Huntsmanadvance materials) formulated polyamidoamineadduct with catalyst

(3) Pigments and fillers

micaceous iron oxide (45ndash50120583) minus11 calcite(300 mesh) talc (300 mesh) silica powder(300 mesh) and mica (300 mesh) (source DKCorporation (DKC) Indore)superfine zinc dust (5 120583) minus11 (source Bansaltrading company)titanium dioxide (source DuPont)

4 Journal of Coatings

Table 1 STC primer base formulations (mixing ratio (5 1 by volume))

SN STC1 primer base STC2 primer base Primerrsquos hardenerIngredients Wt Ingredients Wt Ingredients Wt

1 Epoxy resin 20 Epoxy resin 20 Modified polyamidoamine adduct 945

2Pigments Pigments

Catalyst 246-Tris (dimethyl amino methyl) phenol 5TiO2 5 TiO2 5Zinc dust 25 MIO 30

3Thixotropic agent 05 Thixotropic agent 05

Thixatrol ST antisettling agent 05

Leveling agent 05 Leveling agent 05Dispersing agent 1 Dispersing agent 1

4

Fillers FillersTalc 5 Talc 5

Calcite 10 Calcite 10Silica powder 10 Silica powder 10

Mica 10

5Polar solvent 3 Polar solvent 3

Xylene 7 Xylene 10Methyl isobutyl ketone 3 Methyl isobutyl ketone 5

(4) Thinner polar solvents (source Monument chemi-cals)

(5) Additives silicone based thixotropic agent (sourceElementis specialties) leveling and surface tensionreducing agent and defoamer and adhesion promotor(source BYK additives and instruments)

(6) Substrates used (source Tata Steel Jamshedpur) hotrolled coil sheet grinded as per Swedish standard st2and st3

22 Coating Formulations See Table 1

23 Processing for Formation Surface Preparation and thenApplication STC1 and STC2 primer base synthesis as perTable 1

(a) Premixing stage the calculated amount of epoxy resinstirred with 3 of polar solvent at high-speed mixerfor 10 minutesWhen temperature reaches up to 40∘Cof resin pour fixed amount of thixotropic agent andmix for 20 minutes It becomes like slurry

(b) Grinding stage

(i) the uniform dispersion of pigments was carriedout with slurry and dispersing agent in singledisc bead mill using 1mm sized glass beadsas grinding media filled up to disc level Theprocess was continued until 30 minutes

(ii) the uniform dispersion of extendersfillers wascarried out and continued until fineness of dis-persionThe estimated time for grinding was 2ndash25 hours until hegmann gauge 5 was achieved

(c) Thinning stage here the uniformly distributed pig-ment slurry was added with left over resin solution

solvents and leveling additive to adjust the viscosityand flow property as requiredThe thinning was donein high-speed disk disperser for approximately 30minutes

24 Coating Characterization Table 2 summarizes the prop-erties of different types of liquid polymer base and hardenerswith their significant FT-IR peaks and surface tension STC1and STC2 both have lower surface tension which proves theirmore surface tolerant tendency as compared to others

25 Surface Preparation and FilmDeposition of Substrate Thesurface preparation was carried out bymanual method as perSwedish standard st2 and st3 The substrate was subjected tocleaning by means of emery paper of 60120583m grit size thencleaned with acetone to remove oil grease and nonadherentdirt particles The prepared substrates were applied withvarious primer and top coat systems Here the applicationwas carried out by means of brush application methodApplied coating thickness of primer after drying in one coatwas maintained up to 100 120583m and then second coat wasapplied after nail hardness of the coating The total thicknessof dried coating was obtained up to 200120583m The hard drycuring time was approximately 8ndash10 hours

26 Parameters of Applicability of Coating Systems Table 3summarizes the applicability of different types of coatings indifferent surface conditions which is the minimum passingcriteria to be any surface tolerant coating This criterion canbe justified by their value of pull off adhesion and makingthe film uniform From this table it is observed that allbenchmark products are not capable to make a uniformfilm over moist wet and oil contaminated surfaces (nopull off adhesion possible) but STC1 and STC2 are bothcapable of making the uniform film over moist wet and

Journal of Coatings 5

Table 2 In can properties of the various coatings

Systems High constitute ofingredients Polymer base Cross-linker Hard dry Main FT-IR peaks Surface tension

(newtonmeter)

Benchmark 1 Ti Mg Si and Al Epoxy resin Triethylenetetraminewith catalyst 14ndash16 hours Strong band

SindashO(asymm stret)includedTindashO(Stret) -800ndash1110 cmminus1

3042

Benchmark 2 Si and little amountof Ti and Mg Epoxy resin Triethylenetetramine

with catalyst 14ndash16 hours 3175

Benchmark 3 Si and littleamount of Ti Epoxy resin Triethylenetetramine

with catalyst 12ndash14 hours 3361

STC1 Zn Ti SiBisphenol A basedepoxy resin with

Zn dust

Fomulatedpolyamidoamine

adduct8ndash10 hours ZnndashO at 454 cmminus1 2992

STC2 Fe Ti SiBisphenol A basedepoxy resin with

MIO flakes

Fomulatedpolyamidoamine

adduct8ndash10 hours FendashO at 560 cmminus1 2920

Table 3 Tests for evaluating uniformity and adhesion properties of the films

Surface conditions SystemsBenchmark 1 Benchmark 2 Benchmark 3 STC1 STC2

Applicability

Moisture No uniform filmformation

No uniform filmformation

No uniform filmformation

Uniform filmformed

Uniform filmformed

Oil contaminatedNo uniform film

formationNo uniform film

formationNo uniform film

formationUniform film

formedUniform film

formed

ST2ST3(properlyprepared)

Uniform filmformed

Uniform filmformed

Uniform filmformed

Uniform filmformed

Uniform filmformed

Pull offadhesion(PSI)

Moist

Not possible as noadhesionuniformfilm formationbecause of highsurface tension

Not possible as noadhesionuniformfilm formationbecause of highsurface tension

Not possible as noadhesionuniformfilm formationbecause of highsurface tension

Tested and foundto be 49 (cohesive

failure

Tested and foundto be 47 (cohesive

failure)

Oil contaminated

Not possible as noadhesionuniformfilm formationbecause of highsurface tension

Not possible as noadhesionuniformfilm formationbecause of highsurface tension

Not possible as noadhesionuniformfilm formation

Tested and foundto be

48MPa (cohesivefailure)

Tested and foundto be 46 (cohesive

failure)

ST2 (thoroughlyprepared)

5MPa(adhesion failure)

54MPa(cohesive failure)

49MPa(adhesion failure)

54MPa (cohesivefailure)

52MPa (cohesivefailure)

oil contaminated surfaces so pull off adhesion test can bedone over these surfaces (passing criteria to be a surfacetolerant coating) All products formuniformfilm on properlyprepared surfaces

3 Results and Discussions

31 Chemical Bonding Analysis by FT-IR Spectroscopy Allspectra were recorded ranging from 3300 to 450 cmminus1 wavenumber by using Magna-IR TM spectrometer 550 (Nicolet)equipped with DTGS detector and averaging of 32 scansChemical bonding between the molecules was character-ized by FT-IR spectra FT-IR spectroscopy is a methodto detect functional groups by transition in vibrationallevel of the molecules like aliphatic CH3 stretching fallsin 2850ndash3000 cmminus1 Absorption peaks of other functional

groups involved in coating systems are shown in Table 4and Figure 4 The presence of the absorption peaks of CH3stretching and CndashN stretching shows that the basic structureof base polymer matrix of STC2 is not changed after theaddition of MIO While in benchmark products there are nosignificant absorption peaks of FendashO and ZnndashO in spectraas shown in Figure 4 and Table 4 which suggest no metallicoxide present in the benchmark coating systems

32 Surface Morphology by SemEdax Analysis Scanningelectron microscopy pictures were taken using Hitachi S-3400N microscope (acceleration voltage 15 kV)

SEM was used to determine the sample surface topogra-phy and to get the idea of the distribution of the pigmentspresent in primer STC1 and primer STC2 EDAX analysiswas used to evaluate elemental composition of the coatingson the surface region SEMmicrographs of primer STC1 and

6 Journal of Coatings

Table 4 Chemical bonding analysis by FT-IR spectroscopy

Wave number (cmminus1) Chemical analysis3000ndash2850 cmminus1 Aliphatic ndashCH2 and CH3 stretching900ndash1250 cmminus1 ndashCndashNstretching shows the reaction of epoxy and aliphatic amine454 cmminus1 ZnndashOstretching vibration Obtained in STC1 only560 cmminus1 FendashOstretching Obtained in STC2 only1000ndash1260 cmminus1 ndashCndashO coupled with CndashC 997904rArr CndashCndashO800ndash1110 cmminus1 Strong band SindashOasymmetric stretching included TindashOStretching

600ndash950 cmminus1 TindashO(stretching) only the bands of some widespread pigments overlapped with several other pigments1600ndash1650 cmminus1 Quadrant Stretching of phenyl ring which shows the presence of epoxy resin1490ndash1540 cmminus1 AromaticradicCndashC which shows the presence of epoxy resin

3000 2500 2000 1500 100060

70

80

90

100

110

STC2STC1

STC2STC1

29211607

14681233

15081451

11761240

999

1013

869 721

661607822

600 550 500 45020

40

60

80

100

560

454

Tran

smitt

ance

()

Tran

smitt

ance

()

Wavenumber (cmminus1) Wavenumber (cmminus1)

(a)

3000 2500 2000 1500 100060

70

80

90

100

110

Tran

smitt

ance

()

Tran

smitt

ance

()

Benchmark 1Benchmark 2Benchmark 3

Benchmark 1Benchmark 2Benchmark 3

29231643

1505

14551507

1239 825

8721008

10131244

1176 825

1028

777

800 769687

600 550 500 45020

40

60

80

100

Wavenumber (cmminus1) Wavenumber (cmminus1)

(b)

Figure 4 Comparative FTIR results of (a) STC1 with STC2 (b) benchmark products

primer STC2 (Figure 5) show the homogenous dispersion ofZn particles MIO flakes and other fillers indicate good com-patibility between resin and filler particles while in otherssome agglomeration of silica particles occur which show theheterogenous dispersion indicating the weak compatibility

between the resin and filler particles This agglomerationof silica particles in benchmark coating generates internalstresses and cracks in coating so they do not provide sufficientcorrosion protection of substrate However this uniformdistribution of Zn and MIO particles reduces the internal

Journal of Coatings 7

(a) (b)

(c) (d)

(e)

Figure 5 SEMmicrographs of samples (a) STC1 (b) STC2 (c) benchmark 1 (d) benchmark 2 and (e) benchmark 3

stresses and cracking and also provides sufficient corrosionand barrier protection EDAX images as shown in Figure 6confirm the high percentage of zinc content (which is notavailable in benchmark coatings) in primer STC1 and pres-ence ofMIO in primer STC2 which are themain constituentsproviding cathodic and barrier protection respectively

33 Mechanical Testing Taber abrasion test (ASTM D4060-10) in this test coated panels (4 in times 4 in) were abraded withthe help of abrasive wheels wheel number CS-17 (Rubber +Al2O3) the wheel was 127mm thick and had an externaldiameter of 519mm A test of 1000 cycles was done toobserve the weight loss in the coating This test method hasbeen useful in evaluating the abrasion resistance of attached

coatings Taber abrasion test showed the wear resistance ofthe coatings As seen from Table 5 it is confirmed that boththe STC1 and STC2 coatings behave as good wear resistancedue to the presence of Zn and MIO flakes comparable toother products which indicate good crosslinking density ofthe primer

Pull off adhesion test (ASTMD4541) this test determineseither the greatest perpendicular force (in tension) that asurface area can bear before a plug of material is detachedor whether the surface remains intact at a prescribed force(passfail) Failure will occur along the weakest plane withinthe system comprised of the test fixture adhesive coatingsystem and substrate and will be exposed by the fracturesurface From Figure 7 and Table 5 it is observed that

8 Journal of Coatings

times102

100

80

60

40

20

0

1 2 3 4 5 6 7 8 9

Zn

Zn Zn

COTi Ti

SiAl Au

(keV)

Full scale counts 9403 Cursor 9972keV23 counts

Sample 4(1) pt3

(a)

times102

0

50

40

30

20

10

1 2 3 4 5 6 7 8 9

C

O

Ti

Ti

SiAl Au

Fe

Fe

Fe

Ca

(keV)

Full scale counts 3321 Cursor 9972keV10 counts

Sample 5(1) pt3

(b)

times102

0

50

40

30

20

10

60

0 2 4 6 8 10

C

O

Ti

TiSi

Al

AuAu FeCa

Mg

(keV)

Full scale counts 4644 Sample 1(1) pt2 Cursor 10221 keV15 counts

(c)

times102

80

60

40

20

0

0 2 4 6 8 10

CO

TiTi

Si

Au AuMg

(keV)

Full scale counts 6673 Sample 2(1) pt2 Cursor 10221 keV10 counts

(d)

times102

80

60

40

20

0

0 2 4 6 8 10

CO

Ti

Ti

Si

Au AuAu

(keV)

Full scale counts 11604

140

120

100

Sample 3(1) pt4 Cursor 10221 keV10 counts

(e)

Figure 6 EDAX images of samples (a) STC1 (b) STC2 (c) benchmark 1 (d) benchmark 2 and (e) benchmark 3

the STC1 and STC2underwent cohesive adhesion failureThisshows that the adhesion of the coatings was better than theother products which experienced adhesion failures

Results show that mechanical interlocking and chemicalinteractions throughout the interface are better in STC1 andSTC2 coatings as compared to other products in whichadhesion strength decreased The adhesion of STC2 is dueto MIO flakes which is oriented parallel to the substrateand reacts well with resin which improves the chemicalbonding between the MIO flakes and the resin This givesimprovement in interfacial strength

Impact resistance test (ASTM D2247) this test methodcovers a procedure for rapidly deforming by impact a coatingfilm and its substrate and for evaluating the effect of suchdeformation It has been observed from Table 5 that theSTC1 and STC2 systems surpassed the maximum height ofimpact and have maximum impact energy Sine both systems(STC1 and STC2) were synthesized by using polyamidoaminehardener (polyamine with a long chain fatty acid) which ishelpful in improving the coating flexibility while in bench-mark products polyamine curatives have been added which

is not sufficient to improving the flexibility of coating systemsbecause of short chain length In case of STC2 the MIOflakes in the coating induces stress relaxation eliminate stresspropagation residual stresses and reduce internal stressesFigure 8 shows the panels of coating systems after impacttest The MIO flakes transform and absorb energy whichprevents crack propagation and growing up when the coatingis subjected to an external stress and it will result in theimprovement of the coating flexibility The improvementof the coating flexibility will lead to improvement in thecohesion between the coating and substrate finally In otherproducts there is no MIO flakes and zinc which may be theresult of their low impact strength in case of benchmarks 1and 3

Contact angle measurement (ASTM D7734) this mea-surement was done by goniometer This test is useful forcharacterizing the wettability of surfaces A low advancingcontact angle value (lt45∘) is indicative of wetting and anglesof 10 to 20∘ are indicative of excellent wetting Water canbe used as a test liquid to establish whether a surfaceis hydrophilic (angle lt45∘) hydrophobic (angle gt90∘) or

Journal of Coatings 9

Benchmark 1

(a)

Benchmark 2

(b)

Benchmark 3

(c)

STC1

(d)

STC2

(e)

Figure 7 Pull off adhesion test images of samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

somewhere in between (angle of 45 to 90∘) All coatings werehydrophilic in nature as their contact angle is less than 90∘For coating to be hydrophobic the contact anglemust be equalto or greater than 90∘ (Table 5 and Figure 9)

Tensile test (ASTM D638) this test method is designedto produce tensile property data for the control and specifi-cation of plastic materials by using ultimate tensile strengthmachine From the tensile strength data shown in Table 5it can be concluded that primer STC1 and primer STC2show the tensile strength 1037MPa and 1058MPa which arehigher as compared to other competitive products This maybe due to better bonding strength between epoxy matrix andthe respective pigments (Zn MIO) When the coating underload the stress is transferred from hard pigment to softerepoxy matrixThese pigments provide the good combinationof strength and toughness to the coating which results ingood tensile strength

Flexibility test (ASTM D522) and scratch resistance(ASTMD7027-13) flexibility test methods cover the determi-nation of the resistance to cracking (flexibility) of attached

organic coatings on substrates when elongated by usingconical mandrel bend testerThe specimen is clamped againsta conical mandrel and is bent around the mandrel by aroller mounted on a hand operated lever The diameter ofthe mandrel at the point where the coating starts to crackcan be determined from a scale marked on the specimenclamp Scratch resistance test method is able to characterizethe scratch resistance of polymers by measuring many signif-icant material parameters Table 5 shows that all the coatingsystems passed the maximum bending angle and scratchresistance test (Table 5)

34 Corrosion Studies

341 Salt Spray Test (ASTM B117) Samples were placed incorrosion-resistant self-supporting polyethylene casing Saltspray test provides a controlled corrosive environment whichhas been utilized to produce relative corrosion resistanceinformation for specimens of metals and coated metalsexposed in a given test chamber The coated panels were

10 Journal of Coatings

Benchmark 1

(a)

Benchmark 2

(b)

Benchmark 3

(c)

STC1

(d)

STC2

(e)

Figure 8 Impact resistance test of coated samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

exposed for 2000 hours in salt spray chamber The saltspray chamber was maintained at 35∘C containing 35NaClsolution Figure 10 shows the coated panels at zero 500 1000and 2000 hours After 500 hours initiation of blistering anddelamination took place in benchmark coatings and numberof blisters increased Increased susceptibility of blistering anddelamination may be due to the increased ionic permeabilityof the coating and the formation of amine carbamate (formedby absorbing carbon dioxide and moisture present in atmo-sphere by polyamine curative) over coating surface which is aclear indication of blushing As a comparison to others STC1provided efficient protective function against delaminationaround scribed areas ensured intense galvanic function of theprimer The other products show significant corrosion nearthe scribed areas large blisters and delamination Table 6summarizes the changes that took place in panels during saltspray exposure

342 Electrochemical Test Electrochemical tests were doneby using an electrochemical analyzer CH 604C from CH

instruments USA A three-electrode glass cell equipped witha platinum counter electrode an AgAgClCl- referenceelectrode with uncoated and coated substrates was used forthe electrochemical measurements Electrochemical mea-surements were performed under extreme environmentalconditions consisting of an aqueous air exposed sodiumchloride 35 NaCl solution at room temperature Eachsamplemasked by paraffin and only left 10 cm2 (10lowast 10) areain the solution The working electrode included an electricalconnection wire which was initially attaching the surface ofsample with conducting glue Samples were allowed to stabi-lize at their open circuit potential (OCP) The corrosion rateof coatings was measured by immersion studies conducted in35 wt NaCl solution at room temperature after 2000 hrs ofsalt spray exposure

343 Electrochemical Polarization Test Potentiodynamicpolarization was performed at 001 Vsec scan rate From thepolarization curves (Figure 11) and the data from Table 6 it is

Journal of Coatings 11

(a) (b)

(c) (d)

(e)

Figure 9 Contact angle test of coated samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

clear that the STC1 has higher OCP and lower current density(29 times 10minus7 A cmminus2) and corrosion rate as compared to MIObased STC2 and other benchmark coatingsThis is due to thepresence of zinc oxide which provides cathodic protection tothe substrate initially

Later due to formation of the corrosion product that isZnO the zinc in the system gets consumed and the formedproduct which provides barrier protection to the substrate Inthe case of STC2 theMIOflakes are responsible for providingbarrier protection but since there is no zinc its corrosion rateis higher than STC1 So it is confirmed that the other productshave higher current densities and corrosion rate than theSTC1 and STC2 due to their lack of cathodic protection as

well as less barrier protection because of the absence of zincand MIO flakes in coating material

344 Durability Test All electrochemical impedance spec-troscopy (EIS) spectra were acquired at the open circuitpotential in a frequency range from 10Hz to 1000Hz withac excitation amplitude of 5mVs in a 35 NaCl solutionat room temperature The durability of the coating systemswas estimated by exposing the samples at zero 500 1000 and2000 hours The pore resistance of the coatings is calculatedby plotting bode plots at respective hours

Initially the STC1 shows excellent barrier protectionowing to the homogenous distribution of zinc particles It has

12 Journal of Coatings

At 500 hours At 1000 hours At 2000 hoursAt 0 hour

(a)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(b)

At 500 hours At 1000 hours At 2000 hoursAt 0 hour

(c)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(d)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(e)

Figure 10 Salt spray images of coated panels at 0 500 1000 and 2000 hours (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1and (e) STC2

been observed that from zero to 500 hours there is decreasein pore resistance from log (Zohm) 65 to 48 this may bedue to initiation of corrosion process due to percolation ofthe electrolyte solution After that from 500 to 2000 hrs thereis not much change in pore resistance due to the consumedzinc that formed the corrosion product as ZnO as shown in

bode plots (Figure 12) This is attributed to filling up of voidspaces of the coatings by corrosion products of Zn whichprovide additional barrier protection In STC2 theMIOplaysa key role for providing barrier protection to the substrateIt provides the permeability allowing the transport of watervapor into and out of the film which is helpful in preventing

Journal of Coatings 13

Table 5 Comparative mechanical test results of different kinds of surface tolerant coatings

Benchmark 1 Benchmark 2 Benchmark 3 STC1 STC2

Pull off adhesion (Mpa) 5Mpa 54Mpa 49Mpa 54Mpa 52MpaAdhesion failure Cohesive failure Adhesion failure Cohesive failure Cohesive failure

Impact energy load4730 kgmax height 2310158401015840

2318 J 2688 J 1854 J 2688 J 2688 J

Scratch resistance 10Kg passed 10Kg passed 10Kg passed 10Kg passed 10Kg passedFlexibility 140∘ passed 140∘ passed 140∘ passed 140∘ passed 140∘ passedTensile strength 846Mpa 576MPA 507MPa 1037MPa 1058MPaTaber abrasion results byweight loss (gm) 01277 00945 02080 00981 01073

Contact angle 5534 5234 6224 7474 6720

Table 6 Comparative corrosion test results of different kinds of surface tolerant coatings

SystemsSalt spray test (SST) Log (119885Ohm) Corrosion rate

(mpy-miles peryear)0ndash500 hours 500ndash1000 hours 1000ndash2000 hours 0 hour 500 hours 1000 hours 2000

hours

Benchmark 1Initiation of

blistering at 300hours

Number ofblisters incresed

Large blisters atthe centre and

edges65 48 38 2 3036mpy

Benchmark 2Initiation of

blistering at 350hours

Number ofblisters incresed

Number ofblisters increased 55 42 33 29 0795mpy

Benchmark 3 No blisteringLarge blisters atthe centre and

edges

Large number ofsmall edges 38 32 3 29 0420mpy

STC1 No blistering No blisteringInitiation of

blistering at 1600hours

75 48 42 41 0133mpy

STC2 No blistering No blisteringInitiation of

blistering at 1500hours

65 55 48 41 0311mpy

blistering and delamination even under severe temperaturegradients From Figure 13 it can be seen that initially theSTC1 shows higher value of coating resistance and the slope isless steep than the STC2The results show that the coatings atthis time were good shielding layers with large impedancesand the matrix was protected well After 500 hrs the poreresistance started decreasing assuming that the electrolytesolution was penetrating through the pores of the coatings(Figure 13 and Table 6) This could be because there was nopath in the coatings that allowed the electrolyte to reach thesubstrate with increasing exposure time The coating layerwas gradually attacked and thinned down by the electrolytewhich led to a decrease in the coating resistance (119877119901) becauseelectrolyte was transported to the metal substrate throughionic conducting paths in the coating The other benchmarkproducts show relatively less coating resistance

4 Conclusions

(1) Zinc dust pigmented surface tolerant coating (STC1)and micaceous iron oxide pigmented surface tolerant

14 12 10 08 06 04 02 00

log

(cur

rent

A)

Potential (V versus Calomel)

Benchmark 1Benchmark 2Benchmark 3

STC1STC2

minus100

minus95

minus90

minus85

minus80

minus75

minus70

minus65

minus60

minus55

minus50

minus45

Figure 11 Comparative Tafel plots of STC1 and 2 and benchmarks1 2 and 3

14 Journal of Coatings

16 20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

9

500 hours1000 hours

2000 hours0 hour

log

(ZO

hm)

log (freqHz)

(a)

20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

log (freqHz)

500 hours1000 hours

0 hour2000 hours

log

(ZO

hm)

(b)

18 21 24 27 30 33 36 39 42 45 4824

26

28

30

32

34

36

38

0 hours500 hours

2000 hours1000 hours

log (freqHz)

log

(ZO

hm)

(c)

16 20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

500 hours2000 hours

0 hour1000 hours

log (freqHz)

log

(ZO

hm)

(d)

20 24 28 32 36 40 44 48 5220

25

30

35

40

45

50

55

60

65

1000 hours2000 hours

500 hours0 hour

log (freqHz)

log

(ZO

hm)

(e)

Figure 12 Bode plots of various coating systems (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

Journal of Coatings 15

0 500 1000 1500 20000

1

2

3

4

5

6

7

8

Time (h)

Benchmark 1Benchmark 2Benchmark 3

STC1STC2

log

(ZO

hm)

Figure 13 Pore resistance with time for various coating systems

coating (STC2) were found to form a uniform coatingfilm over moist oil contaminated and surface pre-pared hot rolled sheets Excellent surface compatibil-ity to wet surface and good interfacial adhesion maybe due to low surface tension (28Nm) of the coatingscompared to competitive coatings (gt30Nm)

(2) The results of impact resistance tensile strength abra-sion resistance scratch resistance flexibility and pulloff adhesion were found superior than other availableproducts

(3) Anticorrosive pigments such as zinc dust (responsiblefor superior cathodic protection because of its lowerreduction potential than iron) and MIO (flaky shapewhich provide torturous path to the penetration ofcorrosive electrolytes) in the system have shown sig-nificant resistance against migration of chloride ionsand water and the free space between the particle andthe resin was less and thus restricted the penetrationof electrolyte through the pores in the coating filmThis is evident for high pore resistance over time in35 wt NaCl solution The rate of corrosion is alsofound 23 times less in 35 wt NaCl as compared tocompetitive products

(4) Marine simulation corrosion test as per ASTM B 117has shown significant delay in blister formation Thisis due to presence of anticorrosive pigments

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank Stanvac-Superon group forproviding funding and IIT Bombay and Tata Steel Industry

for providing research facilities for this work The authorswould like to thank all the Research Associate team also

References

[1] G C Soltz ldquoThe effects of substrate contaminates on the lifeof epoxy coatings in sea waterrdquo NSRP Report 0329 NationalShipbuilding Research Program 1991

[2] S B R Appleman S Boocock R E F Weaver and G CSoltz ldquoEffect of surface contaminates on coating liferdquo USDepartment of Transportation Federal Highway Administra-tion Publication FHWA-RD-91-011 1991

[3] National Steel and Shipbuilding NSRP Report ldquoPower ToolCleaning an alternate for abrasive blastingrdquo 1993

[4] J W Peart Evaluation of Coatings Applied on Less than IdealSurfaces withPeterson builders inc sturgeon bay Wis USA1995

[5] ldquoCuring Agent for Epoxy Resinsrdquo Three Bond Technical News1990

[6] N Rajgopalan and A S Khanna ldquoEffect of nano-ZnO in low-ering yellowing of aliphatic amine cured DGEBA-based epoxycoatings onUV exposurerdquo International Journal of Scientific andResearch vol 3 no 4 2013

[7] H Lee and K Neville Epoxy Resins Their Synthesis and Char-acterization and Curing of Epoxy Resins Their Applications andTechnology McGraw Hill

[8] Z W Wicks F N Jones and S P Pappas ldquoOrganic coatingsscience and technologyrdquo Dyes and Pigments vol 45 pp 85ndash862000

[9] L S Salem ldquoEpoxies for steelrdquo Journal of Protective Coatings andLinings vol 13 pp 77ndash98 1996

[10] M Ebert et al Polymer vol 32 no 3 p 139 1991[11] S Swier G van Assche W Vuchelen and B VanMele ldquoRole of

complex formation in the polymerization kinetics of modifiedepoxy-amine systemsrdquoMacromolecules vol 38 no 6 pp 2281ndash2288 2005

[12] S Shreepathi P Bajaj and B P Mallik ldquoElectrochemical imp-edance spectroscopy investigations of epoxy zinc rich coatingsrole of Zn content on corrosion protection mechanismrdquo Elec-trochimica Acta vol 55 no 18 pp 5129ndash5134 2010

[13] P A Soslashrensen S Kiil K Dam-Johansen and C E WeinellldquoAnticorrosive coatings a reviewrdquo Journal of Coatings Technol-ogy Research vol 6 no 2 pp 135ndash176 2009

[14] A Ruvolo-Filho and M Magaton ldquoEvaluating barrier proper-ties of acrylic polyurethane and aliphatic polyurethane coatingsloaded with micaceous iron oxide or red iron oxiderdquo PolymerPlastics Technology and Engineering vol 48 no 7 pp 682ndash6952009

[15] C Giudice J C Benftez and M M Linares ldquoZinc-rich epoxyprimers based on lamellar zinc dustrdquo Surface Coatings Interna-tional vol 80 no 6 pp 279ndash284 1997

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

2 Journal of Coatings

Scratch

Steel

Zinc primer

Top coat

(a)

Active zinc Corrosion productSteel

Scratch

Zinc primer

Top coat

(b)

Inactive zincSteel Corrosion product

Scratch

Zinc primer

Top coat

(c)

Figure 1 Mechanisms of a zinc coating system (a) scribe or scratch is introduced down to the steel surface (b) near scratch zinc becomesactive while zinc-iron corrosion products are being built up (c) zinc becomes inactive but the coating provides only barrier and inhibitiveprotection

tough with excellent surface protection chemical resistantflexible with high strength hard and good heat and electricalresistant [5 6] Other important applications include repair ofcracks andfissures in structural concrete above or underwaterand as adhesives for ceramics Apart from its excellentadhesion the surface tolerant properties also depend onthe pigments additives in the epoxy coating which is alsoresponsible for cathodic as well as barrier protection [7 8]

The viscosity adhesion flexibility impact resistance andsubstrate wetting directly depend on molecular weight ofunreacted epoxy resin while cross-linking density solventresistance and hardness decrease as molecular weight ofunreacted epoxy resin decreases [9] Formation of epoxyresin is the combination of bisphenol A (used for hightemperature and chemical resistance) and epichlorohydrinin presence of alkaline and the resultant is diglycidyl etherof bisphenol A (DGEBA) which is formed after extractingunreacted phenol and acetone [10]

Epoxy resins have the ability to transform readily fromthe liquid state to tough and hard solids This hardening isaccomplished by addition of chemically active reagent knownas curing agent (hardener) Dry time penetration and wet-tability depend upon hardener which cross-linked with resinand provide high chemical resistant with good flexibility Inthis paper cycloaliphatic amines are used as a hardener (roomtemperature curing and convenient handling) because theseamines provide good adhesion as their compatibility with

epoxy and easy availability of lone pairs on nitrogen atom(because of noninvolvement in aromaticity) to zinc and ironsurfaces (chemiadsorption) as compared to aromatic aminesThere is a crosslinking structure formed after curing whichis in between cycloaliphatic amine and epoxy resin due tothe polar bonds interaction of epoxy resin with available lonepairs of nitrogen atom of cycloaliphatic amine [9ndash11]

Many pigments can be used with epoxy resin but wehave chosen zinc pigment because of its lower potential Theperformance of zinc depends on ratio of pigment volumeconcentration (PVC) to critical pigment volume concentra-tion (CPVC) If the ratio is lt1 then it will provide the barrierprotection If the ratio is gt1 then it will provide the cathodicprotection but influences its permeability and mechanicalproperties But the sacrificial action of zinc starts up onlywhen there is uninterrupted contact between metal particlesthat is infiltration path [12] So zinc primers are widely usedin various aggressive atmospheres such as offshore industrialand so forth because of its distinctive property of metalprotection even after the scribe or any mechanical damageto the coating which provides good sacrificial protection atthe early stage and the alkaline nature and low solubilityof corrosion products of zinc provides additional barrierprotection at the later stage as shown in Figure 1 [13]

Type of pigment or filler used in organic coating acts asbarrier and is of crucial importance to the pigment-polymermatrix interaction because undercoat layer increases the free

Journal of Coatings 3

Substrate

UV rays

Pigment particles

Figure 2 The flip-flop effect showing protection against ultraviolet(UV)

mean path for the diffusion of water oxygen and ions Themost common lamellar pigments are MIO flakes of glassmetallic Al particles Zn dust and so forth [14] Zinc withepoxies provides films with moderate porosity Specially for-mulated intermediate andor topcoats are required to over-come blistering over such zinc-based primers (zinc primer isthe zinc dust spherical lamellar or combination of both thatis dispersed in organic epoxies resin) By lowering the zincpigment content in the formulation application blisteringproblem can be solved by scarifying the primerrsquos galvanicproperties Performance of zinc primers also depends on themorphology of the Zn particle smaller and lamellar particlesgive better results than larger and spherical particles [15]

Figure 3 shows the lamellar MIO creating tortuous pathfor water and micaceous iron oxide (MIO) is iron oxidein a form that resembles mica a highly structured layeredmineral The lamellar shape of this micaceous form of ironoxide (high volumetric pigment concentration) offers greatlyenhanced barrier protection due to its tendency to orientparallel to the substrate thereby increase the mean freepath for the diffusion of the aggressive species The lamellarnature and shiny surface appearance of MIO pigments offerultraviolet protection (reflecting barrier to the light) andprotect against blistering and delamination to the underlyingepoxy system This mechanism of protection is known asflip-flop effect as shown in Figure 2 Epoxy and enamelbased coatings normally chalk on exposure to ultraviolet rayshowever in coatings pigmented with MIO only the resin onthe surface of the uppermost MIO particles is exposed toultraviolet rays and will chalk [14]

In this paper solvent borne epoxy mastic as a primerwas synthesized by using bisphenol A based epoxy resinmodifying with zinc dust and MIO It was observed thatMIO and Zinc dust are used in coatings as a barrier andcathodic protection respectively and it improves mechanicaland corrosion properties of coatingsThe emphasis was givento the development of MIO and Zinc dust incorporated intoepoxy based coating So in order to achieve the objectivetwo types of systems (two types of surface tolerant coatingsystems STC1 and STC2 were developed (1) STC1 comprisestwo coat of epoxy mastic primer with zinc dust and (2) STC2

Substrate

Lamellar pigment particles

Water droplets

Substrate

Spherical pigment particles

Water droplets

Figure 3 Lamellar MIO creating tortuous path for water when thewater permeates

comprises two coat of epoxymastic withMIO)were preparedand characterized with optimized concentration of MIO andzinc dust with commercially available coating systems whichare not suitable for application on partially cleaned surfaceprepared according to St2St3 standards The coating wasevaluated for mechanical and corrosion resistance propertiesfor steel as a primer coating

2 Experimental Procedure

21 Materials and Reagents

(1) Epoxy resins unmodified epoxy resin derived frombisphenol A-epoxy equivalent weight (EEW) 185ndash190 Source Aditya birla chemicals (Thailand) LtdThailand

(2) Amine hardener or curing agent (source Huntsmanadvance materials) formulated polyamidoamineadduct with catalyst

(3) Pigments and fillers

micaceous iron oxide (45ndash50120583) minus11 calcite(300 mesh) talc (300 mesh) silica powder(300 mesh) and mica (300 mesh) (source DKCorporation (DKC) Indore)superfine zinc dust (5 120583) minus11 (source Bansaltrading company)titanium dioxide (source DuPont)

4 Journal of Coatings

Table 1 STC primer base formulations (mixing ratio (5 1 by volume))

SN STC1 primer base STC2 primer base Primerrsquos hardenerIngredients Wt Ingredients Wt Ingredients Wt

1 Epoxy resin 20 Epoxy resin 20 Modified polyamidoamine adduct 945

2Pigments Pigments

Catalyst 246-Tris (dimethyl amino methyl) phenol 5TiO2 5 TiO2 5Zinc dust 25 MIO 30

3Thixotropic agent 05 Thixotropic agent 05

Thixatrol ST antisettling agent 05

Leveling agent 05 Leveling agent 05Dispersing agent 1 Dispersing agent 1

4

Fillers FillersTalc 5 Talc 5

Calcite 10 Calcite 10Silica powder 10 Silica powder 10

Mica 10

5Polar solvent 3 Polar solvent 3

Xylene 7 Xylene 10Methyl isobutyl ketone 3 Methyl isobutyl ketone 5

(4) Thinner polar solvents (source Monument chemi-cals)

(5) Additives silicone based thixotropic agent (sourceElementis specialties) leveling and surface tensionreducing agent and defoamer and adhesion promotor(source BYK additives and instruments)

(6) Substrates used (source Tata Steel Jamshedpur) hotrolled coil sheet grinded as per Swedish standard st2and st3

22 Coating Formulations See Table 1

23 Processing for Formation Surface Preparation and thenApplication STC1 and STC2 primer base synthesis as perTable 1

(a) Premixing stage the calculated amount of epoxy resinstirred with 3 of polar solvent at high-speed mixerfor 10 minutesWhen temperature reaches up to 40∘Cof resin pour fixed amount of thixotropic agent andmix for 20 minutes It becomes like slurry

(b) Grinding stage

(i) the uniform dispersion of pigments was carriedout with slurry and dispersing agent in singledisc bead mill using 1mm sized glass beadsas grinding media filled up to disc level Theprocess was continued until 30 minutes

(ii) the uniform dispersion of extendersfillers wascarried out and continued until fineness of dis-persionThe estimated time for grinding was 2ndash25 hours until hegmann gauge 5 was achieved

(c) Thinning stage here the uniformly distributed pig-ment slurry was added with left over resin solution

solvents and leveling additive to adjust the viscosityand flow property as requiredThe thinning was donein high-speed disk disperser for approximately 30minutes

24 Coating Characterization Table 2 summarizes the prop-erties of different types of liquid polymer base and hardenerswith their significant FT-IR peaks and surface tension STC1and STC2 both have lower surface tension which proves theirmore surface tolerant tendency as compared to others

25 Surface Preparation and FilmDeposition of Substrate Thesurface preparation was carried out bymanual method as perSwedish standard st2 and st3 The substrate was subjected tocleaning by means of emery paper of 60120583m grit size thencleaned with acetone to remove oil grease and nonadherentdirt particles The prepared substrates were applied withvarious primer and top coat systems Here the applicationwas carried out by means of brush application methodApplied coating thickness of primer after drying in one coatwas maintained up to 100 120583m and then second coat wasapplied after nail hardness of the coating The total thicknessof dried coating was obtained up to 200120583m The hard drycuring time was approximately 8ndash10 hours

26 Parameters of Applicability of Coating Systems Table 3summarizes the applicability of different types of coatings indifferent surface conditions which is the minimum passingcriteria to be any surface tolerant coating This criterion canbe justified by their value of pull off adhesion and makingthe film uniform From this table it is observed that allbenchmark products are not capable to make a uniformfilm over moist wet and oil contaminated surfaces (nopull off adhesion possible) but STC1 and STC2 are bothcapable of making the uniform film over moist wet and

Journal of Coatings 5

Table 2 In can properties of the various coatings

Systems High constitute ofingredients Polymer base Cross-linker Hard dry Main FT-IR peaks Surface tension

(newtonmeter)

Benchmark 1 Ti Mg Si and Al Epoxy resin Triethylenetetraminewith catalyst 14ndash16 hours Strong band

SindashO(asymm stret)includedTindashO(Stret) -800ndash1110 cmminus1

3042

Benchmark 2 Si and little amountof Ti and Mg Epoxy resin Triethylenetetramine

with catalyst 14ndash16 hours 3175

Benchmark 3 Si and littleamount of Ti Epoxy resin Triethylenetetramine

with catalyst 12ndash14 hours 3361

STC1 Zn Ti SiBisphenol A basedepoxy resin with

Zn dust

Fomulatedpolyamidoamine

adduct8ndash10 hours ZnndashO at 454 cmminus1 2992

STC2 Fe Ti SiBisphenol A basedepoxy resin with

MIO flakes

Fomulatedpolyamidoamine

adduct8ndash10 hours FendashO at 560 cmminus1 2920

Table 3 Tests for evaluating uniformity and adhesion properties of the films

Surface conditions SystemsBenchmark 1 Benchmark 2 Benchmark 3 STC1 STC2

Applicability

Moisture No uniform filmformation

No uniform filmformation

No uniform filmformation

Uniform filmformed

Uniform filmformed

Oil contaminatedNo uniform film

formationNo uniform film

formationNo uniform film

formationUniform film

formedUniform film

formed

ST2ST3(properlyprepared)

Uniform filmformed

Uniform filmformed

Uniform filmformed

Uniform filmformed

Uniform filmformed

Pull offadhesion(PSI)

Moist

Not possible as noadhesionuniformfilm formationbecause of highsurface tension

Not possible as noadhesionuniformfilm formationbecause of highsurface tension

Not possible as noadhesionuniformfilm formationbecause of highsurface tension

Tested and foundto be 49 (cohesive

failure

Tested and foundto be 47 (cohesive

failure)

Oil contaminated

Not possible as noadhesionuniformfilm formationbecause of highsurface tension

Not possible as noadhesionuniformfilm formationbecause of highsurface tension

Not possible as noadhesionuniformfilm formation

Tested and foundto be

48MPa (cohesivefailure)

Tested and foundto be 46 (cohesive

failure)

ST2 (thoroughlyprepared)

5MPa(adhesion failure)

54MPa(cohesive failure)

49MPa(adhesion failure)

54MPa (cohesivefailure)

52MPa (cohesivefailure)

oil contaminated surfaces so pull off adhesion test can bedone over these surfaces (passing criteria to be a surfacetolerant coating) All products formuniformfilm on properlyprepared surfaces

3 Results and Discussions

31 Chemical Bonding Analysis by FT-IR Spectroscopy Allspectra were recorded ranging from 3300 to 450 cmminus1 wavenumber by using Magna-IR TM spectrometer 550 (Nicolet)equipped with DTGS detector and averaging of 32 scansChemical bonding between the molecules was character-ized by FT-IR spectra FT-IR spectroscopy is a methodto detect functional groups by transition in vibrationallevel of the molecules like aliphatic CH3 stretching fallsin 2850ndash3000 cmminus1 Absorption peaks of other functional

groups involved in coating systems are shown in Table 4and Figure 4 The presence of the absorption peaks of CH3stretching and CndashN stretching shows that the basic structureof base polymer matrix of STC2 is not changed after theaddition of MIO While in benchmark products there are nosignificant absorption peaks of FendashO and ZnndashO in spectraas shown in Figure 4 and Table 4 which suggest no metallicoxide present in the benchmark coating systems

32 Surface Morphology by SemEdax Analysis Scanningelectron microscopy pictures were taken using Hitachi S-3400N microscope (acceleration voltage 15 kV)

SEM was used to determine the sample surface topogra-phy and to get the idea of the distribution of the pigmentspresent in primer STC1 and primer STC2 EDAX analysiswas used to evaluate elemental composition of the coatingson the surface region SEMmicrographs of primer STC1 and

6 Journal of Coatings

Table 4 Chemical bonding analysis by FT-IR spectroscopy

Wave number (cmminus1) Chemical analysis3000ndash2850 cmminus1 Aliphatic ndashCH2 and CH3 stretching900ndash1250 cmminus1 ndashCndashNstretching shows the reaction of epoxy and aliphatic amine454 cmminus1 ZnndashOstretching vibration Obtained in STC1 only560 cmminus1 FendashOstretching Obtained in STC2 only1000ndash1260 cmminus1 ndashCndashO coupled with CndashC 997904rArr CndashCndashO800ndash1110 cmminus1 Strong band SindashOasymmetric stretching included TindashOStretching

600ndash950 cmminus1 TindashO(stretching) only the bands of some widespread pigments overlapped with several other pigments1600ndash1650 cmminus1 Quadrant Stretching of phenyl ring which shows the presence of epoxy resin1490ndash1540 cmminus1 AromaticradicCndashC which shows the presence of epoxy resin

3000 2500 2000 1500 100060

70

80

90

100

110

STC2STC1

STC2STC1

29211607

14681233

15081451

11761240

999

1013

869 721

661607822

600 550 500 45020

40

60

80

100

560

454

Tran

smitt

ance

()

Tran

smitt

ance

()

Wavenumber (cmminus1) Wavenumber (cmminus1)

(a)

3000 2500 2000 1500 100060

70

80

90

100

110

Tran

smitt

ance

()

Tran

smitt

ance

()

Benchmark 1Benchmark 2Benchmark 3

Benchmark 1Benchmark 2Benchmark 3

29231643

1505

14551507

1239 825

8721008

10131244

1176 825

1028

777

800 769687

600 550 500 45020

40

60

80

100

Wavenumber (cmminus1) Wavenumber (cmminus1)

(b)

Figure 4 Comparative FTIR results of (a) STC1 with STC2 (b) benchmark products

primer STC2 (Figure 5) show the homogenous dispersion ofZn particles MIO flakes and other fillers indicate good com-patibility between resin and filler particles while in otherssome agglomeration of silica particles occur which show theheterogenous dispersion indicating the weak compatibility

between the resin and filler particles This agglomerationof silica particles in benchmark coating generates internalstresses and cracks in coating so they do not provide sufficientcorrosion protection of substrate However this uniformdistribution of Zn and MIO particles reduces the internal

Journal of Coatings 7

(a) (b)

(c) (d)

(e)

Figure 5 SEMmicrographs of samples (a) STC1 (b) STC2 (c) benchmark 1 (d) benchmark 2 and (e) benchmark 3

stresses and cracking and also provides sufficient corrosionand barrier protection EDAX images as shown in Figure 6confirm the high percentage of zinc content (which is notavailable in benchmark coatings) in primer STC1 and pres-ence ofMIO in primer STC2 which are themain constituentsproviding cathodic and barrier protection respectively

33 Mechanical Testing Taber abrasion test (ASTM D4060-10) in this test coated panels (4 in times 4 in) were abraded withthe help of abrasive wheels wheel number CS-17 (Rubber +Al2O3) the wheel was 127mm thick and had an externaldiameter of 519mm A test of 1000 cycles was done toobserve the weight loss in the coating This test method hasbeen useful in evaluating the abrasion resistance of attached

coatings Taber abrasion test showed the wear resistance ofthe coatings As seen from Table 5 it is confirmed that boththe STC1 and STC2 coatings behave as good wear resistancedue to the presence of Zn and MIO flakes comparable toother products which indicate good crosslinking density ofthe primer

Pull off adhesion test (ASTMD4541) this test determineseither the greatest perpendicular force (in tension) that asurface area can bear before a plug of material is detachedor whether the surface remains intact at a prescribed force(passfail) Failure will occur along the weakest plane withinthe system comprised of the test fixture adhesive coatingsystem and substrate and will be exposed by the fracturesurface From Figure 7 and Table 5 it is observed that

8 Journal of Coatings

times102

100

80

60

40

20

0

1 2 3 4 5 6 7 8 9

Zn

Zn Zn

COTi Ti

SiAl Au

(keV)

Full scale counts 9403 Cursor 9972keV23 counts

Sample 4(1) pt3

(a)

times102

0

50

40

30

20

10

1 2 3 4 5 6 7 8 9

C

O

Ti

Ti

SiAl Au

Fe

Fe

Fe

Ca

(keV)

Full scale counts 3321 Cursor 9972keV10 counts

Sample 5(1) pt3

(b)

times102

0

50

40

30

20

10

60

0 2 4 6 8 10

C

O

Ti

TiSi

Al

AuAu FeCa

Mg

(keV)

Full scale counts 4644 Sample 1(1) pt2 Cursor 10221 keV15 counts

(c)

times102

80

60

40

20

0

0 2 4 6 8 10

CO

TiTi

Si

Au AuMg

(keV)

Full scale counts 6673 Sample 2(1) pt2 Cursor 10221 keV10 counts

(d)

times102

80

60

40

20

0

0 2 4 6 8 10

CO

Ti

Ti

Si

Au AuAu

(keV)

Full scale counts 11604

140

120

100

Sample 3(1) pt4 Cursor 10221 keV10 counts

(e)

Figure 6 EDAX images of samples (a) STC1 (b) STC2 (c) benchmark 1 (d) benchmark 2 and (e) benchmark 3

the STC1 and STC2underwent cohesive adhesion failureThisshows that the adhesion of the coatings was better than theother products which experienced adhesion failures

Results show that mechanical interlocking and chemicalinteractions throughout the interface are better in STC1 andSTC2 coatings as compared to other products in whichadhesion strength decreased The adhesion of STC2 is dueto MIO flakes which is oriented parallel to the substrateand reacts well with resin which improves the chemicalbonding between the MIO flakes and the resin This givesimprovement in interfacial strength

Impact resistance test (ASTM D2247) this test methodcovers a procedure for rapidly deforming by impact a coatingfilm and its substrate and for evaluating the effect of suchdeformation It has been observed from Table 5 that theSTC1 and STC2 systems surpassed the maximum height ofimpact and have maximum impact energy Sine both systems(STC1 and STC2) were synthesized by using polyamidoaminehardener (polyamine with a long chain fatty acid) which ishelpful in improving the coating flexibility while in bench-mark products polyamine curatives have been added which

is not sufficient to improving the flexibility of coating systemsbecause of short chain length In case of STC2 the MIOflakes in the coating induces stress relaxation eliminate stresspropagation residual stresses and reduce internal stressesFigure 8 shows the panels of coating systems after impacttest The MIO flakes transform and absorb energy whichprevents crack propagation and growing up when the coatingis subjected to an external stress and it will result in theimprovement of the coating flexibility The improvementof the coating flexibility will lead to improvement in thecohesion between the coating and substrate finally In otherproducts there is no MIO flakes and zinc which may be theresult of their low impact strength in case of benchmarks 1and 3

Contact angle measurement (ASTM D7734) this mea-surement was done by goniometer This test is useful forcharacterizing the wettability of surfaces A low advancingcontact angle value (lt45∘) is indicative of wetting and anglesof 10 to 20∘ are indicative of excellent wetting Water canbe used as a test liquid to establish whether a surfaceis hydrophilic (angle lt45∘) hydrophobic (angle gt90∘) or

Journal of Coatings 9

Benchmark 1

(a)

Benchmark 2

(b)

Benchmark 3

(c)

STC1

(d)

STC2

(e)

Figure 7 Pull off adhesion test images of samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

somewhere in between (angle of 45 to 90∘) All coatings werehydrophilic in nature as their contact angle is less than 90∘For coating to be hydrophobic the contact anglemust be equalto or greater than 90∘ (Table 5 and Figure 9)

Tensile test (ASTM D638) this test method is designedto produce tensile property data for the control and specifi-cation of plastic materials by using ultimate tensile strengthmachine From the tensile strength data shown in Table 5it can be concluded that primer STC1 and primer STC2show the tensile strength 1037MPa and 1058MPa which arehigher as compared to other competitive products This maybe due to better bonding strength between epoxy matrix andthe respective pigments (Zn MIO) When the coating underload the stress is transferred from hard pigment to softerepoxy matrixThese pigments provide the good combinationof strength and toughness to the coating which results ingood tensile strength

Flexibility test (ASTM D522) and scratch resistance(ASTMD7027-13) flexibility test methods cover the determi-nation of the resistance to cracking (flexibility) of attached

organic coatings on substrates when elongated by usingconical mandrel bend testerThe specimen is clamped againsta conical mandrel and is bent around the mandrel by aroller mounted on a hand operated lever The diameter ofthe mandrel at the point where the coating starts to crackcan be determined from a scale marked on the specimenclamp Scratch resistance test method is able to characterizethe scratch resistance of polymers by measuring many signif-icant material parameters Table 5 shows that all the coatingsystems passed the maximum bending angle and scratchresistance test (Table 5)

34 Corrosion Studies

341 Salt Spray Test (ASTM B117) Samples were placed incorrosion-resistant self-supporting polyethylene casing Saltspray test provides a controlled corrosive environment whichhas been utilized to produce relative corrosion resistanceinformation for specimens of metals and coated metalsexposed in a given test chamber The coated panels were

10 Journal of Coatings

Benchmark 1

(a)

Benchmark 2

(b)

Benchmark 3

(c)

STC1

(d)

STC2

(e)

Figure 8 Impact resistance test of coated samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

exposed for 2000 hours in salt spray chamber The saltspray chamber was maintained at 35∘C containing 35NaClsolution Figure 10 shows the coated panels at zero 500 1000and 2000 hours After 500 hours initiation of blistering anddelamination took place in benchmark coatings and numberof blisters increased Increased susceptibility of blistering anddelamination may be due to the increased ionic permeabilityof the coating and the formation of amine carbamate (formedby absorbing carbon dioxide and moisture present in atmo-sphere by polyamine curative) over coating surface which is aclear indication of blushing As a comparison to others STC1provided efficient protective function against delaminationaround scribed areas ensured intense galvanic function of theprimer The other products show significant corrosion nearthe scribed areas large blisters and delamination Table 6summarizes the changes that took place in panels during saltspray exposure

342 Electrochemical Test Electrochemical tests were doneby using an electrochemical analyzer CH 604C from CH

instruments USA A three-electrode glass cell equipped witha platinum counter electrode an AgAgClCl- referenceelectrode with uncoated and coated substrates was used forthe electrochemical measurements Electrochemical mea-surements were performed under extreme environmentalconditions consisting of an aqueous air exposed sodiumchloride 35 NaCl solution at room temperature Eachsamplemasked by paraffin and only left 10 cm2 (10lowast 10) areain the solution The working electrode included an electricalconnection wire which was initially attaching the surface ofsample with conducting glue Samples were allowed to stabi-lize at their open circuit potential (OCP) The corrosion rateof coatings was measured by immersion studies conducted in35 wt NaCl solution at room temperature after 2000 hrs ofsalt spray exposure

343 Electrochemical Polarization Test Potentiodynamicpolarization was performed at 001 Vsec scan rate From thepolarization curves (Figure 11) and the data from Table 6 it is

Journal of Coatings 11

(a) (b)

(c) (d)

(e)

Figure 9 Contact angle test of coated samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

clear that the STC1 has higher OCP and lower current density(29 times 10minus7 A cmminus2) and corrosion rate as compared to MIObased STC2 and other benchmark coatingsThis is due to thepresence of zinc oxide which provides cathodic protection tothe substrate initially

Later due to formation of the corrosion product that isZnO the zinc in the system gets consumed and the formedproduct which provides barrier protection to the substrate Inthe case of STC2 theMIOflakes are responsible for providingbarrier protection but since there is no zinc its corrosion rateis higher than STC1 So it is confirmed that the other productshave higher current densities and corrosion rate than theSTC1 and STC2 due to their lack of cathodic protection as

well as less barrier protection because of the absence of zincand MIO flakes in coating material

344 Durability Test All electrochemical impedance spec-troscopy (EIS) spectra were acquired at the open circuitpotential in a frequency range from 10Hz to 1000Hz withac excitation amplitude of 5mVs in a 35 NaCl solutionat room temperature The durability of the coating systemswas estimated by exposing the samples at zero 500 1000 and2000 hours The pore resistance of the coatings is calculatedby plotting bode plots at respective hours

Initially the STC1 shows excellent barrier protectionowing to the homogenous distribution of zinc particles It has

12 Journal of Coatings

At 500 hours At 1000 hours At 2000 hoursAt 0 hour

(a)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(b)

At 500 hours At 1000 hours At 2000 hoursAt 0 hour

(c)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(d)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(e)

Figure 10 Salt spray images of coated panels at 0 500 1000 and 2000 hours (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1and (e) STC2

been observed that from zero to 500 hours there is decreasein pore resistance from log (Zohm) 65 to 48 this may bedue to initiation of corrosion process due to percolation ofthe electrolyte solution After that from 500 to 2000 hrs thereis not much change in pore resistance due to the consumedzinc that formed the corrosion product as ZnO as shown in

bode plots (Figure 12) This is attributed to filling up of voidspaces of the coatings by corrosion products of Zn whichprovide additional barrier protection In STC2 theMIOplaysa key role for providing barrier protection to the substrateIt provides the permeability allowing the transport of watervapor into and out of the film which is helpful in preventing

Journal of Coatings 13

Table 5 Comparative mechanical test results of different kinds of surface tolerant coatings

Benchmark 1 Benchmark 2 Benchmark 3 STC1 STC2

Pull off adhesion (Mpa) 5Mpa 54Mpa 49Mpa 54Mpa 52MpaAdhesion failure Cohesive failure Adhesion failure Cohesive failure Cohesive failure

Impact energy load4730 kgmax height 2310158401015840

2318 J 2688 J 1854 J 2688 J 2688 J

Scratch resistance 10Kg passed 10Kg passed 10Kg passed 10Kg passed 10Kg passedFlexibility 140∘ passed 140∘ passed 140∘ passed 140∘ passed 140∘ passedTensile strength 846Mpa 576MPA 507MPa 1037MPa 1058MPaTaber abrasion results byweight loss (gm) 01277 00945 02080 00981 01073

Contact angle 5534 5234 6224 7474 6720

Table 6 Comparative corrosion test results of different kinds of surface tolerant coatings

SystemsSalt spray test (SST) Log (119885Ohm) Corrosion rate

(mpy-miles peryear)0ndash500 hours 500ndash1000 hours 1000ndash2000 hours 0 hour 500 hours 1000 hours 2000

hours

Benchmark 1Initiation of

blistering at 300hours

Number ofblisters incresed

Large blisters atthe centre and

edges65 48 38 2 3036mpy

Benchmark 2Initiation of

blistering at 350hours

Number ofblisters incresed

Number ofblisters increased 55 42 33 29 0795mpy

Benchmark 3 No blisteringLarge blisters atthe centre and

edges

Large number ofsmall edges 38 32 3 29 0420mpy

STC1 No blistering No blisteringInitiation of

blistering at 1600hours

75 48 42 41 0133mpy

STC2 No blistering No blisteringInitiation of

blistering at 1500hours

65 55 48 41 0311mpy

blistering and delamination even under severe temperaturegradients From Figure 13 it can be seen that initially theSTC1 shows higher value of coating resistance and the slope isless steep than the STC2The results show that the coatings atthis time were good shielding layers with large impedancesand the matrix was protected well After 500 hrs the poreresistance started decreasing assuming that the electrolytesolution was penetrating through the pores of the coatings(Figure 13 and Table 6) This could be because there was nopath in the coatings that allowed the electrolyte to reach thesubstrate with increasing exposure time The coating layerwas gradually attacked and thinned down by the electrolytewhich led to a decrease in the coating resistance (119877119901) becauseelectrolyte was transported to the metal substrate throughionic conducting paths in the coating The other benchmarkproducts show relatively less coating resistance

4 Conclusions

(1) Zinc dust pigmented surface tolerant coating (STC1)and micaceous iron oxide pigmented surface tolerant

14 12 10 08 06 04 02 00

log

(cur

rent

A)

Potential (V versus Calomel)

Benchmark 1Benchmark 2Benchmark 3

STC1STC2

minus100

minus95

minus90

minus85

minus80

minus75

minus70

minus65

minus60

minus55

minus50

minus45

Figure 11 Comparative Tafel plots of STC1 and 2 and benchmarks1 2 and 3

14 Journal of Coatings

16 20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

9

500 hours1000 hours

2000 hours0 hour

log

(ZO

hm)

log (freqHz)

(a)

20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

log (freqHz)

500 hours1000 hours

0 hour2000 hours

log

(ZO

hm)

(b)

18 21 24 27 30 33 36 39 42 45 4824

26

28

30

32

34

36

38

0 hours500 hours

2000 hours1000 hours

log (freqHz)

log

(ZO

hm)

(c)

16 20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

500 hours2000 hours

0 hour1000 hours

log (freqHz)

log

(ZO

hm)

(d)

20 24 28 32 36 40 44 48 5220

25

30

35

40

45

50

55

60

65

1000 hours2000 hours

500 hours0 hour

log (freqHz)

log

(ZO

hm)

(e)

Figure 12 Bode plots of various coating systems (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

Journal of Coatings 15

0 500 1000 1500 20000

1

2

3

4

5

6

7

8

Time (h)

Benchmark 1Benchmark 2Benchmark 3

STC1STC2

log

(ZO

hm)

Figure 13 Pore resistance with time for various coating systems

coating (STC2) were found to form a uniform coatingfilm over moist oil contaminated and surface pre-pared hot rolled sheets Excellent surface compatibil-ity to wet surface and good interfacial adhesion maybe due to low surface tension (28Nm) of the coatingscompared to competitive coatings (gt30Nm)

(2) The results of impact resistance tensile strength abra-sion resistance scratch resistance flexibility and pulloff adhesion were found superior than other availableproducts

(3) Anticorrosive pigments such as zinc dust (responsiblefor superior cathodic protection because of its lowerreduction potential than iron) and MIO (flaky shapewhich provide torturous path to the penetration ofcorrosive electrolytes) in the system have shown sig-nificant resistance against migration of chloride ionsand water and the free space between the particle andthe resin was less and thus restricted the penetrationof electrolyte through the pores in the coating filmThis is evident for high pore resistance over time in35 wt NaCl solution The rate of corrosion is alsofound 23 times less in 35 wt NaCl as compared tocompetitive products

(4) Marine simulation corrosion test as per ASTM B 117has shown significant delay in blister formation Thisis due to presence of anticorrosive pigments

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank Stanvac-Superon group forproviding funding and IIT Bombay and Tata Steel Industry

for providing research facilities for this work The authorswould like to thank all the Research Associate team also

References

[1] G C Soltz ldquoThe effects of substrate contaminates on the lifeof epoxy coatings in sea waterrdquo NSRP Report 0329 NationalShipbuilding Research Program 1991

[2] S B R Appleman S Boocock R E F Weaver and G CSoltz ldquoEffect of surface contaminates on coating liferdquo USDepartment of Transportation Federal Highway Administra-tion Publication FHWA-RD-91-011 1991

[3] National Steel and Shipbuilding NSRP Report ldquoPower ToolCleaning an alternate for abrasive blastingrdquo 1993

[4] J W Peart Evaluation of Coatings Applied on Less than IdealSurfaces withPeterson builders inc sturgeon bay Wis USA1995

[5] ldquoCuring Agent for Epoxy Resinsrdquo Three Bond Technical News1990

[6] N Rajgopalan and A S Khanna ldquoEffect of nano-ZnO in low-ering yellowing of aliphatic amine cured DGEBA-based epoxycoatings onUV exposurerdquo International Journal of Scientific andResearch vol 3 no 4 2013

[7] H Lee and K Neville Epoxy Resins Their Synthesis and Char-acterization and Curing of Epoxy Resins Their Applications andTechnology McGraw Hill

[8] Z W Wicks F N Jones and S P Pappas ldquoOrganic coatingsscience and technologyrdquo Dyes and Pigments vol 45 pp 85ndash862000

[9] L S Salem ldquoEpoxies for steelrdquo Journal of Protective Coatings andLinings vol 13 pp 77ndash98 1996

[10] M Ebert et al Polymer vol 32 no 3 p 139 1991[11] S Swier G van Assche W Vuchelen and B VanMele ldquoRole of

complex formation in the polymerization kinetics of modifiedepoxy-amine systemsrdquoMacromolecules vol 38 no 6 pp 2281ndash2288 2005

[12] S Shreepathi P Bajaj and B P Mallik ldquoElectrochemical imp-edance spectroscopy investigations of epoxy zinc rich coatingsrole of Zn content on corrosion protection mechanismrdquo Elec-trochimica Acta vol 55 no 18 pp 5129ndash5134 2010

[13] P A Soslashrensen S Kiil K Dam-Johansen and C E WeinellldquoAnticorrosive coatings a reviewrdquo Journal of Coatings Technol-ogy Research vol 6 no 2 pp 135ndash176 2009

[14] A Ruvolo-Filho and M Magaton ldquoEvaluating barrier proper-ties of acrylic polyurethane and aliphatic polyurethane coatingsloaded with micaceous iron oxide or red iron oxiderdquo PolymerPlastics Technology and Engineering vol 48 no 7 pp 682ndash6952009

[15] C Giudice J C Benftez and M M Linares ldquoZinc-rich epoxyprimers based on lamellar zinc dustrdquo Surface Coatings Interna-tional vol 80 no 6 pp 279ndash284 1997

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Journal of Coatings 3

Substrate

UV rays

Pigment particles

Figure 2 The flip-flop effect showing protection against ultraviolet(UV)

mean path for the diffusion of water oxygen and ions Themost common lamellar pigments are MIO flakes of glassmetallic Al particles Zn dust and so forth [14] Zinc withepoxies provides films with moderate porosity Specially for-mulated intermediate andor topcoats are required to over-come blistering over such zinc-based primers (zinc primer isthe zinc dust spherical lamellar or combination of both thatis dispersed in organic epoxies resin) By lowering the zincpigment content in the formulation application blisteringproblem can be solved by scarifying the primerrsquos galvanicproperties Performance of zinc primers also depends on themorphology of the Zn particle smaller and lamellar particlesgive better results than larger and spherical particles [15]

Figure 3 shows the lamellar MIO creating tortuous pathfor water and micaceous iron oxide (MIO) is iron oxidein a form that resembles mica a highly structured layeredmineral The lamellar shape of this micaceous form of ironoxide (high volumetric pigment concentration) offers greatlyenhanced barrier protection due to its tendency to orientparallel to the substrate thereby increase the mean freepath for the diffusion of the aggressive species The lamellarnature and shiny surface appearance of MIO pigments offerultraviolet protection (reflecting barrier to the light) andprotect against blistering and delamination to the underlyingepoxy system This mechanism of protection is known asflip-flop effect as shown in Figure 2 Epoxy and enamelbased coatings normally chalk on exposure to ultraviolet rayshowever in coatings pigmented with MIO only the resin onthe surface of the uppermost MIO particles is exposed toultraviolet rays and will chalk [14]

In this paper solvent borne epoxy mastic as a primerwas synthesized by using bisphenol A based epoxy resinmodifying with zinc dust and MIO It was observed thatMIO and Zinc dust are used in coatings as a barrier andcathodic protection respectively and it improves mechanicaland corrosion properties of coatingsThe emphasis was givento the development of MIO and Zinc dust incorporated intoepoxy based coating So in order to achieve the objectivetwo types of systems (two types of surface tolerant coatingsystems STC1 and STC2 were developed (1) STC1 comprisestwo coat of epoxy mastic primer with zinc dust and (2) STC2

Substrate

Lamellar pigment particles

Water droplets

Substrate

Spherical pigment particles

Water droplets

Figure 3 Lamellar MIO creating tortuous path for water when thewater permeates

comprises two coat of epoxymastic withMIO)were preparedand characterized with optimized concentration of MIO andzinc dust with commercially available coating systems whichare not suitable for application on partially cleaned surfaceprepared according to St2St3 standards The coating wasevaluated for mechanical and corrosion resistance propertiesfor steel as a primer coating

2 Experimental Procedure

21 Materials and Reagents

(1) Epoxy resins unmodified epoxy resin derived frombisphenol A-epoxy equivalent weight (EEW) 185ndash190 Source Aditya birla chemicals (Thailand) LtdThailand

(2) Amine hardener or curing agent (source Huntsmanadvance materials) formulated polyamidoamineadduct with catalyst

(3) Pigments and fillers

micaceous iron oxide (45ndash50120583) minus11 calcite(300 mesh) talc (300 mesh) silica powder(300 mesh) and mica (300 mesh) (source DKCorporation (DKC) Indore)superfine zinc dust (5 120583) minus11 (source Bansaltrading company)titanium dioxide (source DuPont)

4 Journal of Coatings

Table 1 STC primer base formulations (mixing ratio (5 1 by volume))

SN STC1 primer base STC2 primer base Primerrsquos hardenerIngredients Wt Ingredients Wt Ingredients Wt

1 Epoxy resin 20 Epoxy resin 20 Modified polyamidoamine adduct 945

2Pigments Pigments

Catalyst 246-Tris (dimethyl amino methyl) phenol 5TiO2 5 TiO2 5Zinc dust 25 MIO 30

3Thixotropic agent 05 Thixotropic agent 05

Thixatrol ST antisettling agent 05

Leveling agent 05 Leveling agent 05Dispersing agent 1 Dispersing agent 1

4

Fillers FillersTalc 5 Talc 5

Calcite 10 Calcite 10Silica powder 10 Silica powder 10

Mica 10

5Polar solvent 3 Polar solvent 3

Xylene 7 Xylene 10Methyl isobutyl ketone 3 Methyl isobutyl ketone 5

(4) Thinner polar solvents (source Monument chemi-cals)

(5) Additives silicone based thixotropic agent (sourceElementis specialties) leveling and surface tensionreducing agent and defoamer and adhesion promotor(source BYK additives and instruments)

(6) Substrates used (source Tata Steel Jamshedpur) hotrolled coil sheet grinded as per Swedish standard st2and st3

22 Coating Formulations See Table 1

23 Processing for Formation Surface Preparation and thenApplication STC1 and STC2 primer base synthesis as perTable 1

(a) Premixing stage the calculated amount of epoxy resinstirred with 3 of polar solvent at high-speed mixerfor 10 minutesWhen temperature reaches up to 40∘Cof resin pour fixed amount of thixotropic agent andmix for 20 minutes It becomes like slurry

(b) Grinding stage

(i) the uniform dispersion of pigments was carriedout with slurry and dispersing agent in singledisc bead mill using 1mm sized glass beadsas grinding media filled up to disc level Theprocess was continued until 30 minutes

(ii) the uniform dispersion of extendersfillers wascarried out and continued until fineness of dis-persionThe estimated time for grinding was 2ndash25 hours until hegmann gauge 5 was achieved

(c) Thinning stage here the uniformly distributed pig-ment slurry was added with left over resin solution

solvents and leveling additive to adjust the viscosityand flow property as requiredThe thinning was donein high-speed disk disperser for approximately 30minutes

24 Coating Characterization Table 2 summarizes the prop-erties of different types of liquid polymer base and hardenerswith their significant FT-IR peaks and surface tension STC1and STC2 both have lower surface tension which proves theirmore surface tolerant tendency as compared to others

25 Surface Preparation and FilmDeposition of Substrate Thesurface preparation was carried out bymanual method as perSwedish standard st2 and st3 The substrate was subjected tocleaning by means of emery paper of 60120583m grit size thencleaned with acetone to remove oil grease and nonadherentdirt particles The prepared substrates were applied withvarious primer and top coat systems Here the applicationwas carried out by means of brush application methodApplied coating thickness of primer after drying in one coatwas maintained up to 100 120583m and then second coat wasapplied after nail hardness of the coating The total thicknessof dried coating was obtained up to 200120583m The hard drycuring time was approximately 8ndash10 hours

26 Parameters of Applicability of Coating Systems Table 3summarizes the applicability of different types of coatings indifferent surface conditions which is the minimum passingcriteria to be any surface tolerant coating This criterion canbe justified by their value of pull off adhesion and makingthe film uniform From this table it is observed that allbenchmark products are not capable to make a uniformfilm over moist wet and oil contaminated surfaces (nopull off adhesion possible) but STC1 and STC2 are bothcapable of making the uniform film over moist wet and

Journal of Coatings 5

Table 2 In can properties of the various coatings

Systems High constitute ofingredients Polymer base Cross-linker Hard dry Main FT-IR peaks Surface tension

(newtonmeter)

Benchmark 1 Ti Mg Si and Al Epoxy resin Triethylenetetraminewith catalyst 14ndash16 hours Strong band

SindashO(asymm stret)includedTindashO(Stret) -800ndash1110 cmminus1

3042

Benchmark 2 Si and little amountof Ti and Mg Epoxy resin Triethylenetetramine

with catalyst 14ndash16 hours 3175

Benchmark 3 Si and littleamount of Ti Epoxy resin Triethylenetetramine

with catalyst 12ndash14 hours 3361

STC1 Zn Ti SiBisphenol A basedepoxy resin with

Zn dust

Fomulatedpolyamidoamine

adduct8ndash10 hours ZnndashO at 454 cmminus1 2992

STC2 Fe Ti SiBisphenol A basedepoxy resin with

MIO flakes

Fomulatedpolyamidoamine

adduct8ndash10 hours FendashO at 560 cmminus1 2920

Table 3 Tests for evaluating uniformity and adhesion properties of the films

Surface conditions SystemsBenchmark 1 Benchmark 2 Benchmark 3 STC1 STC2

Applicability

Moisture No uniform filmformation

No uniform filmformation

No uniform filmformation

Uniform filmformed

Uniform filmformed

Oil contaminatedNo uniform film

formationNo uniform film

formationNo uniform film

formationUniform film

formedUniform film

formed

ST2ST3(properlyprepared)

Uniform filmformed

Uniform filmformed

Uniform filmformed

Uniform filmformed

Uniform filmformed

Pull offadhesion(PSI)

Moist

Not possible as noadhesionuniformfilm formationbecause of highsurface tension

Not possible as noadhesionuniformfilm formationbecause of highsurface tension

Not possible as noadhesionuniformfilm formationbecause of highsurface tension

Tested and foundto be 49 (cohesive

failure

Tested and foundto be 47 (cohesive

failure)

Oil contaminated

Not possible as noadhesionuniformfilm formationbecause of highsurface tension

Not possible as noadhesionuniformfilm formationbecause of highsurface tension

Not possible as noadhesionuniformfilm formation

Tested and foundto be

48MPa (cohesivefailure)

Tested and foundto be 46 (cohesive

failure)

ST2 (thoroughlyprepared)

5MPa(adhesion failure)

54MPa(cohesive failure)

49MPa(adhesion failure)

54MPa (cohesivefailure)

52MPa (cohesivefailure)

oil contaminated surfaces so pull off adhesion test can bedone over these surfaces (passing criteria to be a surfacetolerant coating) All products formuniformfilm on properlyprepared surfaces

3 Results and Discussions

31 Chemical Bonding Analysis by FT-IR Spectroscopy Allspectra were recorded ranging from 3300 to 450 cmminus1 wavenumber by using Magna-IR TM spectrometer 550 (Nicolet)equipped with DTGS detector and averaging of 32 scansChemical bonding between the molecules was character-ized by FT-IR spectra FT-IR spectroscopy is a methodto detect functional groups by transition in vibrationallevel of the molecules like aliphatic CH3 stretching fallsin 2850ndash3000 cmminus1 Absorption peaks of other functional

groups involved in coating systems are shown in Table 4and Figure 4 The presence of the absorption peaks of CH3stretching and CndashN stretching shows that the basic structureof base polymer matrix of STC2 is not changed after theaddition of MIO While in benchmark products there are nosignificant absorption peaks of FendashO and ZnndashO in spectraas shown in Figure 4 and Table 4 which suggest no metallicoxide present in the benchmark coating systems

32 Surface Morphology by SemEdax Analysis Scanningelectron microscopy pictures were taken using Hitachi S-3400N microscope (acceleration voltage 15 kV)

SEM was used to determine the sample surface topogra-phy and to get the idea of the distribution of the pigmentspresent in primer STC1 and primer STC2 EDAX analysiswas used to evaluate elemental composition of the coatingson the surface region SEMmicrographs of primer STC1 and

6 Journal of Coatings

Table 4 Chemical bonding analysis by FT-IR spectroscopy

Wave number (cmminus1) Chemical analysis3000ndash2850 cmminus1 Aliphatic ndashCH2 and CH3 stretching900ndash1250 cmminus1 ndashCndashNstretching shows the reaction of epoxy and aliphatic amine454 cmminus1 ZnndashOstretching vibration Obtained in STC1 only560 cmminus1 FendashOstretching Obtained in STC2 only1000ndash1260 cmminus1 ndashCndashO coupled with CndashC 997904rArr CndashCndashO800ndash1110 cmminus1 Strong band SindashOasymmetric stretching included TindashOStretching

600ndash950 cmminus1 TindashO(stretching) only the bands of some widespread pigments overlapped with several other pigments1600ndash1650 cmminus1 Quadrant Stretching of phenyl ring which shows the presence of epoxy resin1490ndash1540 cmminus1 AromaticradicCndashC which shows the presence of epoxy resin

3000 2500 2000 1500 100060

70

80

90

100

110

STC2STC1

STC2STC1

29211607

14681233

15081451

11761240

999

1013

869 721

661607822

600 550 500 45020

40

60

80

100

560

454

Tran

smitt

ance

()

Tran

smitt

ance

()

Wavenumber (cmminus1) Wavenumber (cmminus1)

(a)

3000 2500 2000 1500 100060

70

80

90

100

110

Tran

smitt

ance

()

Tran

smitt

ance

()

Benchmark 1Benchmark 2Benchmark 3

Benchmark 1Benchmark 2Benchmark 3

29231643

1505

14551507

1239 825

8721008

10131244

1176 825

1028

777

800 769687

600 550 500 45020

40

60

80

100

Wavenumber (cmminus1) Wavenumber (cmminus1)

(b)

Figure 4 Comparative FTIR results of (a) STC1 with STC2 (b) benchmark products

primer STC2 (Figure 5) show the homogenous dispersion ofZn particles MIO flakes and other fillers indicate good com-patibility between resin and filler particles while in otherssome agglomeration of silica particles occur which show theheterogenous dispersion indicating the weak compatibility

between the resin and filler particles This agglomerationof silica particles in benchmark coating generates internalstresses and cracks in coating so they do not provide sufficientcorrosion protection of substrate However this uniformdistribution of Zn and MIO particles reduces the internal

Journal of Coatings 7

(a) (b)

(c) (d)

(e)

Figure 5 SEMmicrographs of samples (a) STC1 (b) STC2 (c) benchmark 1 (d) benchmark 2 and (e) benchmark 3

stresses and cracking and also provides sufficient corrosionand barrier protection EDAX images as shown in Figure 6confirm the high percentage of zinc content (which is notavailable in benchmark coatings) in primer STC1 and pres-ence ofMIO in primer STC2 which are themain constituentsproviding cathodic and barrier protection respectively

33 Mechanical Testing Taber abrasion test (ASTM D4060-10) in this test coated panels (4 in times 4 in) were abraded withthe help of abrasive wheels wheel number CS-17 (Rubber +Al2O3) the wheel was 127mm thick and had an externaldiameter of 519mm A test of 1000 cycles was done toobserve the weight loss in the coating This test method hasbeen useful in evaluating the abrasion resistance of attached

coatings Taber abrasion test showed the wear resistance ofthe coatings As seen from Table 5 it is confirmed that boththe STC1 and STC2 coatings behave as good wear resistancedue to the presence of Zn and MIO flakes comparable toother products which indicate good crosslinking density ofthe primer

Pull off adhesion test (ASTMD4541) this test determineseither the greatest perpendicular force (in tension) that asurface area can bear before a plug of material is detachedor whether the surface remains intact at a prescribed force(passfail) Failure will occur along the weakest plane withinthe system comprised of the test fixture adhesive coatingsystem and substrate and will be exposed by the fracturesurface From Figure 7 and Table 5 it is observed that

8 Journal of Coatings

times102

100

80

60

40

20

0

1 2 3 4 5 6 7 8 9

Zn

Zn Zn

COTi Ti

SiAl Au

(keV)

Full scale counts 9403 Cursor 9972keV23 counts

Sample 4(1) pt3

(a)

times102

0

50

40

30

20

10

1 2 3 4 5 6 7 8 9

C

O

Ti

Ti

SiAl Au

Fe

Fe

Fe

Ca

(keV)

Full scale counts 3321 Cursor 9972keV10 counts

Sample 5(1) pt3

(b)

times102

0

50

40

30

20

10

60

0 2 4 6 8 10

C

O

Ti

TiSi

Al

AuAu FeCa

Mg

(keV)

Full scale counts 4644 Sample 1(1) pt2 Cursor 10221 keV15 counts

(c)

times102

80

60

40

20

0

0 2 4 6 8 10

CO

TiTi

Si

Au AuMg

(keV)

Full scale counts 6673 Sample 2(1) pt2 Cursor 10221 keV10 counts

(d)

times102

80

60

40

20

0

0 2 4 6 8 10

CO

Ti

Ti

Si

Au AuAu

(keV)

Full scale counts 11604

140

120

100

Sample 3(1) pt4 Cursor 10221 keV10 counts

(e)

Figure 6 EDAX images of samples (a) STC1 (b) STC2 (c) benchmark 1 (d) benchmark 2 and (e) benchmark 3

the STC1 and STC2underwent cohesive adhesion failureThisshows that the adhesion of the coatings was better than theother products which experienced adhesion failures

Results show that mechanical interlocking and chemicalinteractions throughout the interface are better in STC1 andSTC2 coatings as compared to other products in whichadhesion strength decreased The adhesion of STC2 is dueto MIO flakes which is oriented parallel to the substrateand reacts well with resin which improves the chemicalbonding between the MIO flakes and the resin This givesimprovement in interfacial strength

Impact resistance test (ASTM D2247) this test methodcovers a procedure for rapidly deforming by impact a coatingfilm and its substrate and for evaluating the effect of suchdeformation It has been observed from Table 5 that theSTC1 and STC2 systems surpassed the maximum height ofimpact and have maximum impact energy Sine both systems(STC1 and STC2) were synthesized by using polyamidoaminehardener (polyamine with a long chain fatty acid) which ishelpful in improving the coating flexibility while in bench-mark products polyamine curatives have been added which

is not sufficient to improving the flexibility of coating systemsbecause of short chain length In case of STC2 the MIOflakes in the coating induces stress relaxation eliminate stresspropagation residual stresses and reduce internal stressesFigure 8 shows the panels of coating systems after impacttest The MIO flakes transform and absorb energy whichprevents crack propagation and growing up when the coatingis subjected to an external stress and it will result in theimprovement of the coating flexibility The improvementof the coating flexibility will lead to improvement in thecohesion between the coating and substrate finally In otherproducts there is no MIO flakes and zinc which may be theresult of their low impact strength in case of benchmarks 1and 3

Contact angle measurement (ASTM D7734) this mea-surement was done by goniometer This test is useful forcharacterizing the wettability of surfaces A low advancingcontact angle value (lt45∘) is indicative of wetting and anglesof 10 to 20∘ are indicative of excellent wetting Water canbe used as a test liquid to establish whether a surfaceis hydrophilic (angle lt45∘) hydrophobic (angle gt90∘) or

Journal of Coatings 9

Benchmark 1

(a)

Benchmark 2

(b)

Benchmark 3

(c)

STC1

(d)

STC2

(e)

Figure 7 Pull off adhesion test images of samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

somewhere in between (angle of 45 to 90∘) All coatings werehydrophilic in nature as their contact angle is less than 90∘For coating to be hydrophobic the contact anglemust be equalto or greater than 90∘ (Table 5 and Figure 9)

Tensile test (ASTM D638) this test method is designedto produce tensile property data for the control and specifi-cation of plastic materials by using ultimate tensile strengthmachine From the tensile strength data shown in Table 5it can be concluded that primer STC1 and primer STC2show the tensile strength 1037MPa and 1058MPa which arehigher as compared to other competitive products This maybe due to better bonding strength between epoxy matrix andthe respective pigments (Zn MIO) When the coating underload the stress is transferred from hard pigment to softerepoxy matrixThese pigments provide the good combinationof strength and toughness to the coating which results ingood tensile strength

Flexibility test (ASTM D522) and scratch resistance(ASTMD7027-13) flexibility test methods cover the determi-nation of the resistance to cracking (flexibility) of attached

organic coatings on substrates when elongated by usingconical mandrel bend testerThe specimen is clamped againsta conical mandrel and is bent around the mandrel by aroller mounted on a hand operated lever The diameter ofthe mandrel at the point where the coating starts to crackcan be determined from a scale marked on the specimenclamp Scratch resistance test method is able to characterizethe scratch resistance of polymers by measuring many signif-icant material parameters Table 5 shows that all the coatingsystems passed the maximum bending angle and scratchresistance test (Table 5)

34 Corrosion Studies

341 Salt Spray Test (ASTM B117) Samples were placed incorrosion-resistant self-supporting polyethylene casing Saltspray test provides a controlled corrosive environment whichhas been utilized to produce relative corrosion resistanceinformation for specimens of metals and coated metalsexposed in a given test chamber The coated panels were

10 Journal of Coatings

Benchmark 1

(a)

Benchmark 2

(b)

Benchmark 3

(c)

STC1

(d)

STC2

(e)

Figure 8 Impact resistance test of coated samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

exposed for 2000 hours in salt spray chamber The saltspray chamber was maintained at 35∘C containing 35NaClsolution Figure 10 shows the coated panels at zero 500 1000and 2000 hours After 500 hours initiation of blistering anddelamination took place in benchmark coatings and numberof blisters increased Increased susceptibility of blistering anddelamination may be due to the increased ionic permeabilityof the coating and the formation of amine carbamate (formedby absorbing carbon dioxide and moisture present in atmo-sphere by polyamine curative) over coating surface which is aclear indication of blushing As a comparison to others STC1provided efficient protective function against delaminationaround scribed areas ensured intense galvanic function of theprimer The other products show significant corrosion nearthe scribed areas large blisters and delamination Table 6summarizes the changes that took place in panels during saltspray exposure

342 Electrochemical Test Electrochemical tests were doneby using an electrochemical analyzer CH 604C from CH

instruments USA A three-electrode glass cell equipped witha platinum counter electrode an AgAgClCl- referenceelectrode with uncoated and coated substrates was used forthe electrochemical measurements Electrochemical mea-surements were performed under extreme environmentalconditions consisting of an aqueous air exposed sodiumchloride 35 NaCl solution at room temperature Eachsamplemasked by paraffin and only left 10 cm2 (10lowast 10) areain the solution The working electrode included an electricalconnection wire which was initially attaching the surface ofsample with conducting glue Samples were allowed to stabi-lize at their open circuit potential (OCP) The corrosion rateof coatings was measured by immersion studies conducted in35 wt NaCl solution at room temperature after 2000 hrs ofsalt spray exposure

343 Electrochemical Polarization Test Potentiodynamicpolarization was performed at 001 Vsec scan rate From thepolarization curves (Figure 11) and the data from Table 6 it is

Journal of Coatings 11

(a) (b)

(c) (d)

(e)

Figure 9 Contact angle test of coated samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

clear that the STC1 has higher OCP and lower current density(29 times 10minus7 A cmminus2) and corrosion rate as compared to MIObased STC2 and other benchmark coatingsThis is due to thepresence of zinc oxide which provides cathodic protection tothe substrate initially

Later due to formation of the corrosion product that isZnO the zinc in the system gets consumed and the formedproduct which provides barrier protection to the substrate Inthe case of STC2 theMIOflakes are responsible for providingbarrier protection but since there is no zinc its corrosion rateis higher than STC1 So it is confirmed that the other productshave higher current densities and corrosion rate than theSTC1 and STC2 due to their lack of cathodic protection as

well as less barrier protection because of the absence of zincand MIO flakes in coating material

344 Durability Test All electrochemical impedance spec-troscopy (EIS) spectra were acquired at the open circuitpotential in a frequency range from 10Hz to 1000Hz withac excitation amplitude of 5mVs in a 35 NaCl solutionat room temperature The durability of the coating systemswas estimated by exposing the samples at zero 500 1000 and2000 hours The pore resistance of the coatings is calculatedby plotting bode plots at respective hours

Initially the STC1 shows excellent barrier protectionowing to the homogenous distribution of zinc particles It has

12 Journal of Coatings

At 500 hours At 1000 hours At 2000 hoursAt 0 hour

(a)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(b)

At 500 hours At 1000 hours At 2000 hoursAt 0 hour

(c)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(d)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(e)

Figure 10 Salt spray images of coated panels at 0 500 1000 and 2000 hours (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1and (e) STC2

been observed that from zero to 500 hours there is decreasein pore resistance from log (Zohm) 65 to 48 this may bedue to initiation of corrosion process due to percolation ofthe electrolyte solution After that from 500 to 2000 hrs thereis not much change in pore resistance due to the consumedzinc that formed the corrosion product as ZnO as shown in

bode plots (Figure 12) This is attributed to filling up of voidspaces of the coatings by corrosion products of Zn whichprovide additional barrier protection In STC2 theMIOplaysa key role for providing barrier protection to the substrateIt provides the permeability allowing the transport of watervapor into and out of the film which is helpful in preventing

Journal of Coatings 13

Table 5 Comparative mechanical test results of different kinds of surface tolerant coatings

Benchmark 1 Benchmark 2 Benchmark 3 STC1 STC2

Pull off adhesion (Mpa) 5Mpa 54Mpa 49Mpa 54Mpa 52MpaAdhesion failure Cohesive failure Adhesion failure Cohesive failure Cohesive failure

Impact energy load4730 kgmax height 2310158401015840

2318 J 2688 J 1854 J 2688 J 2688 J

Scratch resistance 10Kg passed 10Kg passed 10Kg passed 10Kg passed 10Kg passedFlexibility 140∘ passed 140∘ passed 140∘ passed 140∘ passed 140∘ passedTensile strength 846Mpa 576MPA 507MPa 1037MPa 1058MPaTaber abrasion results byweight loss (gm) 01277 00945 02080 00981 01073

Contact angle 5534 5234 6224 7474 6720

Table 6 Comparative corrosion test results of different kinds of surface tolerant coatings

SystemsSalt spray test (SST) Log (119885Ohm) Corrosion rate

(mpy-miles peryear)0ndash500 hours 500ndash1000 hours 1000ndash2000 hours 0 hour 500 hours 1000 hours 2000

hours

Benchmark 1Initiation of

blistering at 300hours

Number ofblisters incresed

Large blisters atthe centre and

edges65 48 38 2 3036mpy

Benchmark 2Initiation of

blistering at 350hours

Number ofblisters incresed

Number ofblisters increased 55 42 33 29 0795mpy

Benchmark 3 No blisteringLarge blisters atthe centre and

edges

Large number ofsmall edges 38 32 3 29 0420mpy

STC1 No blistering No blisteringInitiation of

blistering at 1600hours

75 48 42 41 0133mpy

STC2 No blistering No blisteringInitiation of

blistering at 1500hours

65 55 48 41 0311mpy

blistering and delamination even under severe temperaturegradients From Figure 13 it can be seen that initially theSTC1 shows higher value of coating resistance and the slope isless steep than the STC2The results show that the coatings atthis time were good shielding layers with large impedancesand the matrix was protected well After 500 hrs the poreresistance started decreasing assuming that the electrolytesolution was penetrating through the pores of the coatings(Figure 13 and Table 6) This could be because there was nopath in the coatings that allowed the electrolyte to reach thesubstrate with increasing exposure time The coating layerwas gradually attacked and thinned down by the electrolytewhich led to a decrease in the coating resistance (119877119901) becauseelectrolyte was transported to the metal substrate throughionic conducting paths in the coating The other benchmarkproducts show relatively less coating resistance

4 Conclusions

(1) Zinc dust pigmented surface tolerant coating (STC1)and micaceous iron oxide pigmented surface tolerant

14 12 10 08 06 04 02 00

log

(cur

rent

A)

Potential (V versus Calomel)

Benchmark 1Benchmark 2Benchmark 3

STC1STC2

minus100

minus95

minus90

minus85

minus80

minus75

minus70

minus65

minus60

minus55

minus50

minus45

Figure 11 Comparative Tafel plots of STC1 and 2 and benchmarks1 2 and 3

14 Journal of Coatings

16 20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

9

500 hours1000 hours

2000 hours0 hour

log

(ZO

hm)

log (freqHz)

(a)

20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

log (freqHz)

500 hours1000 hours

0 hour2000 hours

log

(ZO

hm)

(b)

18 21 24 27 30 33 36 39 42 45 4824

26

28

30

32

34

36

38

0 hours500 hours

2000 hours1000 hours

log (freqHz)

log

(ZO

hm)

(c)

16 20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

500 hours2000 hours

0 hour1000 hours

log (freqHz)

log

(ZO

hm)

(d)

20 24 28 32 36 40 44 48 5220

25

30

35

40

45

50

55

60

65

1000 hours2000 hours

500 hours0 hour

log (freqHz)

log

(ZO

hm)

(e)

Figure 12 Bode plots of various coating systems (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

Journal of Coatings 15

0 500 1000 1500 20000

1

2

3

4

5

6

7

8

Time (h)

Benchmark 1Benchmark 2Benchmark 3

STC1STC2

log

(ZO

hm)

Figure 13 Pore resistance with time for various coating systems

coating (STC2) were found to form a uniform coatingfilm over moist oil contaminated and surface pre-pared hot rolled sheets Excellent surface compatibil-ity to wet surface and good interfacial adhesion maybe due to low surface tension (28Nm) of the coatingscompared to competitive coatings (gt30Nm)

(2) The results of impact resistance tensile strength abra-sion resistance scratch resistance flexibility and pulloff adhesion were found superior than other availableproducts

(3) Anticorrosive pigments such as zinc dust (responsiblefor superior cathodic protection because of its lowerreduction potential than iron) and MIO (flaky shapewhich provide torturous path to the penetration ofcorrosive electrolytes) in the system have shown sig-nificant resistance against migration of chloride ionsand water and the free space between the particle andthe resin was less and thus restricted the penetrationof electrolyte through the pores in the coating filmThis is evident for high pore resistance over time in35 wt NaCl solution The rate of corrosion is alsofound 23 times less in 35 wt NaCl as compared tocompetitive products

(4) Marine simulation corrosion test as per ASTM B 117has shown significant delay in blister formation Thisis due to presence of anticorrosive pigments

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank Stanvac-Superon group forproviding funding and IIT Bombay and Tata Steel Industry

for providing research facilities for this work The authorswould like to thank all the Research Associate team also

References

[1] G C Soltz ldquoThe effects of substrate contaminates on the lifeof epoxy coatings in sea waterrdquo NSRP Report 0329 NationalShipbuilding Research Program 1991

[2] S B R Appleman S Boocock R E F Weaver and G CSoltz ldquoEffect of surface contaminates on coating liferdquo USDepartment of Transportation Federal Highway Administra-tion Publication FHWA-RD-91-011 1991

[3] National Steel and Shipbuilding NSRP Report ldquoPower ToolCleaning an alternate for abrasive blastingrdquo 1993

[4] J W Peart Evaluation of Coatings Applied on Less than IdealSurfaces withPeterson builders inc sturgeon bay Wis USA1995

[5] ldquoCuring Agent for Epoxy Resinsrdquo Three Bond Technical News1990

[6] N Rajgopalan and A S Khanna ldquoEffect of nano-ZnO in low-ering yellowing of aliphatic amine cured DGEBA-based epoxycoatings onUV exposurerdquo International Journal of Scientific andResearch vol 3 no 4 2013

[7] H Lee and K Neville Epoxy Resins Their Synthesis and Char-acterization and Curing of Epoxy Resins Their Applications andTechnology McGraw Hill

[8] Z W Wicks F N Jones and S P Pappas ldquoOrganic coatingsscience and technologyrdquo Dyes and Pigments vol 45 pp 85ndash862000

[9] L S Salem ldquoEpoxies for steelrdquo Journal of Protective Coatings andLinings vol 13 pp 77ndash98 1996

[10] M Ebert et al Polymer vol 32 no 3 p 139 1991[11] S Swier G van Assche W Vuchelen and B VanMele ldquoRole of

complex formation in the polymerization kinetics of modifiedepoxy-amine systemsrdquoMacromolecules vol 38 no 6 pp 2281ndash2288 2005

[12] S Shreepathi P Bajaj and B P Mallik ldquoElectrochemical imp-edance spectroscopy investigations of epoxy zinc rich coatingsrole of Zn content on corrosion protection mechanismrdquo Elec-trochimica Acta vol 55 no 18 pp 5129ndash5134 2010

[13] P A Soslashrensen S Kiil K Dam-Johansen and C E WeinellldquoAnticorrosive coatings a reviewrdquo Journal of Coatings Technol-ogy Research vol 6 no 2 pp 135ndash176 2009

[14] A Ruvolo-Filho and M Magaton ldquoEvaluating barrier proper-ties of acrylic polyurethane and aliphatic polyurethane coatingsloaded with micaceous iron oxide or red iron oxiderdquo PolymerPlastics Technology and Engineering vol 48 no 7 pp 682ndash6952009

[15] C Giudice J C Benftez and M M Linares ldquoZinc-rich epoxyprimers based on lamellar zinc dustrdquo Surface Coatings Interna-tional vol 80 no 6 pp 279ndash284 1997

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

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BioMed Research International

MaterialsJournal of

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Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

4 Journal of Coatings

Table 1 STC primer base formulations (mixing ratio (5 1 by volume))

SN STC1 primer base STC2 primer base Primerrsquos hardenerIngredients Wt Ingredients Wt Ingredients Wt

1 Epoxy resin 20 Epoxy resin 20 Modified polyamidoamine adduct 945

2Pigments Pigments

Catalyst 246-Tris (dimethyl amino methyl) phenol 5TiO2 5 TiO2 5Zinc dust 25 MIO 30

3Thixotropic agent 05 Thixotropic agent 05

Thixatrol ST antisettling agent 05

Leveling agent 05 Leveling agent 05Dispersing agent 1 Dispersing agent 1

4

Fillers FillersTalc 5 Talc 5

Calcite 10 Calcite 10Silica powder 10 Silica powder 10

Mica 10

5Polar solvent 3 Polar solvent 3

Xylene 7 Xylene 10Methyl isobutyl ketone 3 Methyl isobutyl ketone 5

(4) Thinner polar solvents (source Monument chemi-cals)

(5) Additives silicone based thixotropic agent (sourceElementis specialties) leveling and surface tensionreducing agent and defoamer and adhesion promotor(source BYK additives and instruments)

(6) Substrates used (source Tata Steel Jamshedpur) hotrolled coil sheet grinded as per Swedish standard st2and st3

22 Coating Formulations See Table 1

23 Processing for Formation Surface Preparation and thenApplication STC1 and STC2 primer base synthesis as perTable 1

(a) Premixing stage the calculated amount of epoxy resinstirred with 3 of polar solvent at high-speed mixerfor 10 minutesWhen temperature reaches up to 40∘Cof resin pour fixed amount of thixotropic agent andmix for 20 minutes It becomes like slurry

(b) Grinding stage

(i) the uniform dispersion of pigments was carriedout with slurry and dispersing agent in singledisc bead mill using 1mm sized glass beadsas grinding media filled up to disc level Theprocess was continued until 30 minutes

(ii) the uniform dispersion of extendersfillers wascarried out and continued until fineness of dis-persionThe estimated time for grinding was 2ndash25 hours until hegmann gauge 5 was achieved

(c) Thinning stage here the uniformly distributed pig-ment slurry was added with left over resin solution

solvents and leveling additive to adjust the viscosityand flow property as requiredThe thinning was donein high-speed disk disperser for approximately 30minutes

24 Coating Characterization Table 2 summarizes the prop-erties of different types of liquid polymer base and hardenerswith their significant FT-IR peaks and surface tension STC1and STC2 both have lower surface tension which proves theirmore surface tolerant tendency as compared to others

25 Surface Preparation and FilmDeposition of Substrate Thesurface preparation was carried out bymanual method as perSwedish standard st2 and st3 The substrate was subjected tocleaning by means of emery paper of 60120583m grit size thencleaned with acetone to remove oil grease and nonadherentdirt particles The prepared substrates were applied withvarious primer and top coat systems Here the applicationwas carried out by means of brush application methodApplied coating thickness of primer after drying in one coatwas maintained up to 100 120583m and then second coat wasapplied after nail hardness of the coating The total thicknessof dried coating was obtained up to 200120583m The hard drycuring time was approximately 8ndash10 hours

26 Parameters of Applicability of Coating Systems Table 3summarizes the applicability of different types of coatings indifferent surface conditions which is the minimum passingcriteria to be any surface tolerant coating This criterion canbe justified by their value of pull off adhesion and makingthe film uniform From this table it is observed that allbenchmark products are not capable to make a uniformfilm over moist wet and oil contaminated surfaces (nopull off adhesion possible) but STC1 and STC2 are bothcapable of making the uniform film over moist wet and

Journal of Coatings 5

Table 2 In can properties of the various coatings

Systems High constitute ofingredients Polymer base Cross-linker Hard dry Main FT-IR peaks Surface tension

(newtonmeter)

Benchmark 1 Ti Mg Si and Al Epoxy resin Triethylenetetraminewith catalyst 14ndash16 hours Strong band

SindashO(asymm stret)includedTindashO(Stret) -800ndash1110 cmminus1

3042

Benchmark 2 Si and little amountof Ti and Mg Epoxy resin Triethylenetetramine

with catalyst 14ndash16 hours 3175

Benchmark 3 Si and littleamount of Ti Epoxy resin Triethylenetetramine

with catalyst 12ndash14 hours 3361

STC1 Zn Ti SiBisphenol A basedepoxy resin with

Zn dust

Fomulatedpolyamidoamine

adduct8ndash10 hours ZnndashO at 454 cmminus1 2992

STC2 Fe Ti SiBisphenol A basedepoxy resin with

MIO flakes

Fomulatedpolyamidoamine

adduct8ndash10 hours FendashO at 560 cmminus1 2920

Table 3 Tests for evaluating uniformity and adhesion properties of the films

Surface conditions SystemsBenchmark 1 Benchmark 2 Benchmark 3 STC1 STC2

Applicability

Moisture No uniform filmformation

No uniform filmformation

No uniform filmformation

Uniform filmformed

Uniform filmformed

Oil contaminatedNo uniform film

formationNo uniform film

formationNo uniform film

formationUniform film

formedUniform film

formed

ST2ST3(properlyprepared)

Uniform filmformed

Uniform filmformed

Uniform filmformed

Uniform filmformed

Uniform filmformed

Pull offadhesion(PSI)

Moist

Not possible as noadhesionuniformfilm formationbecause of highsurface tension

Not possible as noadhesionuniformfilm formationbecause of highsurface tension

Not possible as noadhesionuniformfilm formationbecause of highsurface tension

Tested and foundto be 49 (cohesive

failure

Tested and foundto be 47 (cohesive

failure)

Oil contaminated

Not possible as noadhesionuniformfilm formationbecause of highsurface tension

Not possible as noadhesionuniformfilm formationbecause of highsurface tension

Not possible as noadhesionuniformfilm formation

Tested and foundto be

48MPa (cohesivefailure)

Tested and foundto be 46 (cohesive

failure)

ST2 (thoroughlyprepared)

5MPa(adhesion failure)

54MPa(cohesive failure)

49MPa(adhesion failure)

54MPa (cohesivefailure)

52MPa (cohesivefailure)

oil contaminated surfaces so pull off adhesion test can bedone over these surfaces (passing criteria to be a surfacetolerant coating) All products formuniformfilm on properlyprepared surfaces

3 Results and Discussions

31 Chemical Bonding Analysis by FT-IR Spectroscopy Allspectra were recorded ranging from 3300 to 450 cmminus1 wavenumber by using Magna-IR TM spectrometer 550 (Nicolet)equipped with DTGS detector and averaging of 32 scansChemical bonding between the molecules was character-ized by FT-IR spectra FT-IR spectroscopy is a methodto detect functional groups by transition in vibrationallevel of the molecules like aliphatic CH3 stretching fallsin 2850ndash3000 cmminus1 Absorption peaks of other functional

groups involved in coating systems are shown in Table 4and Figure 4 The presence of the absorption peaks of CH3stretching and CndashN stretching shows that the basic structureof base polymer matrix of STC2 is not changed after theaddition of MIO While in benchmark products there are nosignificant absorption peaks of FendashO and ZnndashO in spectraas shown in Figure 4 and Table 4 which suggest no metallicoxide present in the benchmark coating systems

32 Surface Morphology by SemEdax Analysis Scanningelectron microscopy pictures were taken using Hitachi S-3400N microscope (acceleration voltage 15 kV)

SEM was used to determine the sample surface topogra-phy and to get the idea of the distribution of the pigmentspresent in primer STC1 and primer STC2 EDAX analysiswas used to evaluate elemental composition of the coatingson the surface region SEMmicrographs of primer STC1 and

6 Journal of Coatings

Table 4 Chemical bonding analysis by FT-IR spectroscopy

Wave number (cmminus1) Chemical analysis3000ndash2850 cmminus1 Aliphatic ndashCH2 and CH3 stretching900ndash1250 cmminus1 ndashCndashNstretching shows the reaction of epoxy and aliphatic amine454 cmminus1 ZnndashOstretching vibration Obtained in STC1 only560 cmminus1 FendashOstretching Obtained in STC2 only1000ndash1260 cmminus1 ndashCndashO coupled with CndashC 997904rArr CndashCndashO800ndash1110 cmminus1 Strong band SindashOasymmetric stretching included TindashOStretching

600ndash950 cmminus1 TindashO(stretching) only the bands of some widespread pigments overlapped with several other pigments1600ndash1650 cmminus1 Quadrant Stretching of phenyl ring which shows the presence of epoxy resin1490ndash1540 cmminus1 AromaticradicCndashC which shows the presence of epoxy resin

3000 2500 2000 1500 100060

70

80

90

100

110

STC2STC1

STC2STC1

29211607

14681233

15081451

11761240

999

1013

869 721

661607822

600 550 500 45020

40

60

80

100

560

454

Tran

smitt

ance

()

Tran

smitt

ance

()

Wavenumber (cmminus1) Wavenumber (cmminus1)

(a)

3000 2500 2000 1500 100060

70

80

90

100

110

Tran

smitt

ance

()

Tran

smitt

ance

()

Benchmark 1Benchmark 2Benchmark 3

Benchmark 1Benchmark 2Benchmark 3

29231643

1505

14551507

1239 825

8721008

10131244

1176 825

1028

777

800 769687

600 550 500 45020

40

60

80

100

Wavenumber (cmminus1) Wavenumber (cmminus1)

(b)

Figure 4 Comparative FTIR results of (a) STC1 with STC2 (b) benchmark products

primer STC2 (Figure 5) show the homogenous dispersion ofZn particles MIO flakes and other fillers indicate good com-patibility between resin and filler particles while in otherssome agglomeration of silica particles occur which show theheterogenous dispersion indicating the weak compatibility

between the resin and filler particles This agglomerationof silica particles in benchmark coating generates internalstresses and cracks in coating so they do not provide sufficientcorrosion protection of substrate However this uniformdistribution of Zn and MIO particles reduces the internal

Journal of Coatings 7

(a) (b)

(c) (d)

(e)

Figure 5 SEMmicrographs of samples (a) STC1 (b) STC2 (c) benchmark 1 (d) benchmark 2 and (e) benchmark 3

stresses and cracking and also provides sufficient corrosionand barrier protection EDAX images as shown in Figure 6confirm the high percentage of zinc content (which is notavailable in benchmark coatings) in primer STC1 and pres-ence ofMIO in primer STC2 which are themain constituentsproviding cathodic and barrier protection respectively

33 Mechanical Testing Taber abrasion test (ASTM D4060-10) in this test coated panels (4 in times 4 in) were abraded withthe help of abrasive wheels wheel number CS-17 (Rubber +Al2O3) the wheel was 127mm thick and had an externaldiameter of 519mm A test of 1000 cycles was done toobserve the weight loss in the coating This test method hasbeen useful in evaluating the abrasion resistance of attached

coatings Taber abrasion test showed the wear resistance ofthe coatings As seen from Table 5 it is confirmed that boththe STC1 and STC2 coatings behave as good wear resistancedue to the presence of Zn and MIO flakes comparable toother products which indicate good crosslinking density ofthe primer

Pull off adhesion test (ASTMD4541) this test determineseither the greatest perpendicular force (in tension) that asurface area can bear before a plug of material is detachedor whether the surface remains intact at a prescribed force(passfail) Failure will occur along the weakest plane withinthe system comprised of the test fixture adhesive coatingsystem and substrate and will be exposed by the fracturesurface From Figure 7 and Table 5 it is observed that

8 Journal of Coatings

times102

100

80

60

40

20

0

1 2 3 4 5 6 7 8 9

Zn

Zn Zn

COTi Ti

SiAl Au

(keV)

Full scale counts 9403 Cursor 9972keV23 counts

Sample 4(1) pt3

(a)

times102

0

50

40

30

20

10

1 2 3 4 5 6 7 8 9

C

O

Ti

Ti

SiAl Au

Fe

Fe

Fe

Ca

(keV)

Full scale counts 3321 Cursor 9972keV10 counts

Sample 5(1) pt3

(b)

times102

0

50

40

30

20

10

60

0 2 4 6 8 10

C

O

Ti

TiSi

Al

AuAu FeCa

Mg

(keV)

Full scale counts 4644 Sample 1(1) pt2 Cursor 10221 keV15 counts

(c)

times102

80

60

40

20

0

0 2 4 6 8 10

CO

TiTi

Si

Au AuMg

(keV)

Full scale counts 6673 Sample 2(1) pt2 Cursor 10221 keV10 counts

(d)

times102

80

60

40

20

0

0 2 4 6 8 10

CO

Ti

Ti

Si

Au AuAu

(keV)

Full scale counts 11604

140

120

100

Sample 3(1) pt4 Cursor 10221 keV10 counts

(e)

Figure 6 EDAX images of samples (a) STC1 (b) STC2 (c) benchmark 1 (d) benchmark 2 and (e) benchmark 3

the STC1 and STC2underwent cohesive adhesion failureThisshows that the adhesion of the coatings was better than theother products which experienced adhesion failures

Results show that mechanical interlocking and chemicalinteractions throughout the interface are better in STC1 andSTC2 coatings as compared to other products in whichadhesion strength decreased The adhesion of STC2 is dueto MIO flakes which is oriented parallel to the substrateand reacts well with resin which improves the chemicalbonding between the MIO flakes and the resin This givesimprovement in interfacial strength

Impact resistance test (ASTM D2247) this test methodcovers a procedure for rapidly deforming by impact a coatingfilm and its substrate and for evaluating the effect of suchdeformation It has been observed from Table 5 that theSTC1 and STC2 systems surpassed the maximum height ofimpact and have maximum impact energy Sine both systems(STC1 and STC2) were synthesized by using polyamidoaminehardener (polyamine with a long chain fatty acid) which ishelpful in improving the coating flexibility while in bench-mark products polyamine curatives have been added which

is not sufficient to improving the flexibility of coating systemsbecause of short chain length In case of STC2 the MIOflakes in the coating induces stress relaxation eliminate stresspropagation residual stresses and reduce internal stressesFigure 8 shows the panels of coating systems after impacttest The MIO flakes transform and absorb energy whichprevents crack propagation and growing up when the coatingis subjected to an external stress and it will result in theimprovement of the coating flexibility The improvementof the coating flexibility will lead to improvement in thecohesion between the coating and substrate finally In otherproducts there is no MIO flakes and zinc which may be theresult of their low impact strength in case of benchmarks 1and 3

Contact angle measurement (ASTM D7734) this mea-surement was done by goniometer This test is useful forcharacterizing the wettability of surfaces A low advancingcontact angle value (lt45∘) is indicative of wetting and anglesof 10 to 20∘ are indicative of excellent wetting Water canbe used as a test liquid to establish whether a surfaceis hydrophilic (angle lt45∘) hydrophobic (angle gt90∘) or

Journal of Coatings 9

Benchmark 1

(a)

Benchmark 2

(b)

Benchmark 3

(c)

STC1

(d)

STC2

(e)

Figure 7 Pull off adhesion test images of samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

somewhere in between (angle of 45 to 90∘) All coatings werehydrophilic in nature as their contact angle is less than 90∘For coating to be hydrophobic the contact anglemust be equalto or greater than 90∘ (Table 5 and Figure 9)

Tensile test (ASTM D638) this test method is designedto produce tensile property data for the control and specifi-cation of plastic materials by using ultimate tensile strengthmachine From the tensile strength data shown in Table 5it can be concluded that primer STC1 and primer STC2show the tensile strength 1037MPa and 1058MPa which arehigher as compared to other competitive products This maybe due to better bonding strength between epoxy matrix andthe respective pigments (Zn MIO) When the coating underload the stress is transferred from hard pigment to softerepoxy matrixThese pigments provide the good combinationof strength and toughness to the coating which results ingood tensile strength

Flexibility test (ASTM D522) and scratch resistance(ASTMD7027-13) flexibility test methods cover the determi-nation of the resistance to cracking (flexibility) of attached

organic coatings on substrates when elongated by usingconical mandrel bend testerThe specimen is clamped againsta conical mandrel and is bent around the mandrel by aroller mounted on a hand operated lever The diameter ofthe mandrel at the point where the coating starts to crackcan be determined from a scale marked on the specimenclamp Scratch resistance test method is able to characterizethe scratch resistance of polymers by measuring many signif-icant material parameters Table 5 shows that all the coatingsystems passed the maximum bending angle and scratchresistance test (Table 5)

34 Corrosion Studies

341 Salt Spray Test (ASTM B117) Samples were placed incorrosion-resistant self-supporting polyethylene casing Saltspray test provides a controlled corrosive environment whichhas been utilized to produce relative corrosion resistanceinformation for specimens of metals and coated metalsexposed in a given test chamber The coated panels were

10 Journal of Coatings

Benchmark 1

(a)

Benchmark 2

(b)

Benchmark 3

(c)

STC1

(d)

STC2

(e)

Figure 8 Impact resistance test of coated samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

exposed for 2000 hours in salt spray chamber The saltspray chamber was maintained at 35∘C containing 35NaClsolution Figure 10 shows the coated panels at zero 500 1000and 2000 hours After 500 hours initiation of blistering anddelamination took place in benchmark coatings and numberof blisters increased Increased susceptibility of blistering anddelamination may be due to the increased ionic permeabilityof the coating and the formation of amine carbamate (formedby absorbing carbon dioxide and moisture present in atmo-sphere by polyamine curative) over coating surface which is aclear indication of blushing As a comparison to others STC1provided efficient protective function against delaminationaround scribed areas ensured intense galvanic function of theprimer The other products show significant corrosion nearthe scribed areas large blisters and delamination Table 6summarizes the changes that took place in panels during saltspray exposure

342 Electrochemical Test Electrochemical tests were doneby using an electrochemical analyzer CH 604C from CH

instruments USA A three-electrode glass cell equipped witha platinum counter electrode an AgAgClCl- referenceelectrode with uncoated and coated substrates was used forthe electrochemical measurements Electrochemical mea-surements were performed under extreme environmentalconditions consisting of an aqueous air exposed sodiumchloride 35 NaCl solution at room temperature Eachsamplemasked by paraffin and only left 10 cm2 (10lowast 10) areain the solution The working electrode included an electricalconnection wire which was initially attaching the surface ofsample with conducting glue Samples were allowed to stabi-lize at their open circuit potential (OCP) The corrosion rateof coatings was measured by immersion studies conducted in35 wt NaCl solution at room temperature after 2000 hrs ofsalt spray exposure

343 Electrochemical Polarization Test Potentiodynamicpolarization was performed at 001 Vsec scan rate From thepolarization curves (Figure 11) and the data from Table 6 it is

Journal of Coatings 11

(a) (b)

(c) (d)

(e)

Figure 9 Contact angle test of coated samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

clear that the STC1 has higher OCP and lower current density(29 times 10minus7 A cmminus2) and corrosion rate as compared to MIObased STC2 and other benchmark coatingsThis is due to thepresence of zinc oxide which provides cathodic protection tothe substrate initially

Later due to formation of the corrosion product that isZnO the zinc in the system gets consumed and the formedproduct which provides barrier protection to the substrate Inthe case of STC2 theMIOflakes are responsible for providingbarrier protection but since there is no zinc its corrosion rateis higher than STC1 So it is confirmed that the other productshave higher current densities and corrosion rate than theSTC1 and STC2 due to their lack of cathodic protection as

well as less barrier protection because of the absence of zincand MIO flakes in coating material

344 Durability Test All electrochemical impedance spec-troscopy (EIS) spectra were acquired at the open circuitpotential in a frequency range from 10Hz to 1000Hz withac excitation amplitude of 5mVs in a 35 NaCl solutionat room temperature The durability of the coating systemswas estimated by exposing the samples at zero 500 1000 and2000 hours The pore resistance of the coatings is calculatedby plotting bode plots at respective hours

Initially the STC1 shows excellent barrier protectionowing to the homogenous distribution of zinc particles It has

12 Journal of Coatings

At 500 hours At 1000 hours At 2000 hoursAt 0 hour

(a)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(b)

At 500 hours At 1000 hours At 2000 hoursAt 0 hour

(c)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(d)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(e)

Figure 10 Salt spray images of coated panels at 0 500 1000 and 2000 hours (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1and (e) STC2

been observed that from zero to 500 hours there is decreasein pore resistance from log (Zohm) 65 to 48 this may bedue to initiation of corrosion process due to percolation ofthe electrolyte solution After that from 500 to 2000 hrs thereis not much change in pore resistance due to the consumedzinc that formed the corrosion product as ZnO as shown in

bode plots (Figure 12) This is attributed to filling up of voidspaces of the coatings by corrosion products of Zn whichprovide additional barrier protection In STC2 theMIOplaysa key role for providing barrier protection to the substrateIt provides the permeability allowing the transport of watervapor into and out of the film which is helpful in preventing

Journal of Coatings 13

Table 5 Comparative mechanical test results of different kinds of surface tolerant coatings

Benchmark 1 Benchmark 2 Benchmark 3 STC1 STC2

Pull off adhesion (Mpa) 5Mpa 54Mpa 49Mpa 54Mpa 52MpaAdhesion failure Cohesive failure Adhesion failure Cohesive failure Cohesive failure

Impact energy load4730 kgmax height 2310158401015840

2318 J 2688 J 1854 J 2688 J 2688 J

Scratch resistance 10Kg passed 10Kg passed 10Kg passed 10Kg passed 10Kg passedFlexibility 140∘ passed 140∘ passed 140∘ passed 140∘ passed 140∘ passedTensile strength 846Mpa 576MPA 507MPa 1037MPa 1058MPaTaber abrasion results byweight loss (gm) 01277 00945 02080 00981 01073

Contact angle 5534 5234 6224 7474 6720

Table 6 Comparative corrosion test results of different kinds of surface tolerant coatings

SystemsSalt spray test (SST) Log (119885Ohm) Corrosion rate

(mpy-miles peryear)0ndash500 hours 500ndash1000 hours 1000ndash2000 hours 0 hour 500 hours 1000 hours 2000

hours

Benchmark 1Initiation of

blistering at 300hours

Number ofblisters incresed

Large blisters atthe centre and

edges65 48 38 2 3036mpy

Benchmark 2Initiation of

blistering at 350hours

Number ofblisters incresed

Number ofblisters increased 55 42 33 29 0795mpy

Benchmark 3 No blisteringLarge blisters atthe centre and

edges

Large number ofsmall edges 38 32 3 29 0420mpy

STC1 No blistering No blisteringInitiation of

blistering at 1600hours

75 48 42 41 0133mpy

STC2 No blistering No blisteringInitiation of

blistering at 1500hours

65 55 48 41 0311mpy

blistering and delamination even under severe temperaturegradients From Figure 13 it can be seen that initially theSTC1 shows higher value of coating resistance and the slope isless steep than the STC2The results show that the coatings atthis time were good shielding layers with large impedancesand the matrix was protected well After 500 hrs the poreresistance started decreasing assuming that the electrolytesolution was penetrating through the pores of the coatings(Figure 13 and Table 6) This could be because there was nopath in the coatings that allowed the electrolyte to reach thesubstrate with increasing exposure time The coating layerwas gradually attacked and thinned down by the electrolytewhich led to a decrease in the coating resistance (119877119901) becauseelectrolyte was transported to the metal substrate throughionic conducting paths in the coating The other benchmarkproducts show relatively less coating resistance

4 Conclusions

(1) Zinc dust pigmented surface tolerant coating (STC1)and micaceous iron oxide pigmented surface tolerant

14 12 10 08 06 04 02 00

log

(cur

rent

A)

Potential (V versus Calomel)

Benchmark 1Benchmark 2Benchmark 3

STC1STC2

minus100

minus95

minus90

minus85

minus80

minus75

minus70

minus65

minus60

minus55

minus50

minus45

Figure 11 Comparative Tafel plots of STC1 and 2 and benchmarks1 2 and 3

14 Journal of Coatings

16 20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

9

500 hours1000 hours

2000 hours0 hour

log

(ZO

hm)

log (freqHz)

(a)

20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

log (freqHz)

500 hours1000 hours

0 hour2000 hours

log

(ZO

hm)

(b)

18 21 24 27 30 33 36 39 42 45 4824

26

28

30

32

34

36

38

0 hours500 hours

2000 hours1000 hours

log (freqHz)

log

(ZO

hm)

(c)

16 20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

500 hours2000 hours

0 hour1000 hours

log (freqHz)

log

(ZO

hm)

(d)

20 24 28 32 36 40 44 48 5220

25

30

35

40

45

50

55

60

65

1000 hours2000 hours

500 hours0 hour

log (freqHz)

log

(ZO

hm)

(e)

Figure 12 Bode plots of various coating systems (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

Journal of Coatings 15

0 500 1000 1500 20000

1

2

3

4

5

6

7

8

Time (h)

Benchmark 1Benchmark 2Benchmark 3

STC1STC2

log

(ZO

hm)

Figure 13 Pore resistance with time for various coating systems

coating (STC2) were found to form a uniform coatingfilm over moist oil contaminated and surface pre-pared hot rolled sheets Excellent surface compatibil-ity to wet surface and good interfacial adhesion maybe due to low surface tension (28Nm) of the coatingscompared to competitive coatings (gt30Nm)

(2) The results of impact resistance tensile strength abra-sion resistance scratch resistance flexibility and pulloff adhesion were found superior than other availableproducts

(3) Anticorrosive pigments such as zinc dust (responsiblefor superior cathodic protection because of its lowerreduction potential than iron) and MIO (flaky shapewhich provide torturous path to the penetration ofcorrosive electrolytes) in the system have shown sig-nificant resistance against migration of chloride ionsand water and the free space between the particle andthe resin was less and thus restricted the penetrationof electrolyte through the pores in the coating filmThis is evident for high pore resistance over time in35 wt NaCl solution The rate of corrosion is alsofound 23 times less in 35 wt NaCl as compared tocompetitive products

(4) Marine simulation corrosion test as per ASTM B 117has shown significant delay in blister formation Thisis due to presence of anticorrosive pigments

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank Stanvac-Superon group forproviding funding and IIT Bombay and Tata Steel Industry

for providing research facilities for this work The authorswould like to thank all the Research Associate team also

References

[1] G C Soltz ldquoThe effects of substrate contaminates on the lifeof epoxy coatings in sea waterrdquo NSRP Report 0329 NationalShipbuilding Research Program 1991

[2] S B R Appleman S Boocock R E F Weaver and G CSoltz ldquoEffect of surface contaminates on coating liferdquo USDepartment of Transportation Federal Highway Administra-tion Publication FHWA-RD-91-011 1991

[3] National Steel and Shipbuilding NSRP Report ldquoPower ToolCleaning an alternate for abrasive blastingrdquo 1993

[4] J W Peart Evaluation of Coatings Applied on Less than IdealSurfaces withPeterson builders inc sturgeon bay Wis USA1995

[5] ldquoCuring Agent for Epoxy Resinsrdquo Three Bond Technical News1990

[6] N Rajgopalan and A S Khanna ldquoEffect of nano-ZnO in low-ering yellowing of aliphatic amine cured DGEBA-based epoxycoatings onUV exposurerdquo International Journal of Scientific andResearch vol 3 no 4 2013

[7] H Lee and K Neville Epoxy Resins Their Synthesis and Char-acterization and Curing of Epoxy Resins Their Applications andTechnology McGraw Hill

[8] Z W Wicks F N Jones and S P Pappas ldquoOrganic coatingsscience and technologyrdquo Dyes and Pigments vol 45 pp 85ndash862000

[9] L S Salem ldquoEpoxies for steelrdquo Journal of Protective Coatings andLinings vol 13 pp 77ndash98 1996

[10] M Ebert et al Polymer vol 32 no 3 p 139 1991[11] S Swier G van Assche W Vuchelen and B VanMele ldquoRole of

complex formation in the polymerization kinetics of modifiedepoxy-amine systemsrdquoMacromolecules vol 38 no 6 pp 2281ndash2288 2005

[12] S Shreepathi P Bajaj and B P Mallik ldquoElectrochemical imp-edance spectroscopy investigations of epoxy zinc rich coatingsrole of Zn content on corrosion protection mechanismrdquo Elec-trochimica Acta vol 55 no 18 pp 5129ndash5134 2010

[13] P A Soslashrensen S Kiil K Dam-Johansen and C E WeinellldquoAnticorrosive coatings a reviewrdquo Journal of Coatings Technol-ogy Research vol 6 no 2 pp 135ndash176 2009

[14] A Ruvolo-Filho and M Magaton ldquoEvaluating barrier proper-ties of acrylic polyurethane and aliphatic polyurethane coatingsloaded with micaceous iron oxide or red iron oxiderdquo PolymerPlastics Technology and Engineering vol 48 no 7 pp 682ndash6952009

[15] C Giudice J C Benftez and M M Linares ldquoZinc-rich epoxyprimers based on lamellar zinc dustrdquo Surface Coatings Interna-tional vol 80 no 6 pp 279ndash284 1997

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

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BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Journal of Coatings 5

Table 2 In can properties of the various coatings

Systems High constitute ofingredients Polymer base Cross-linker Hard dry Main FT-IR peaks Surface tension

(newtonmeter)

Benchmark 1 Ti Mg Si and Al Epoxy resin Triethylenetetraminewith catalyst 14ndash16 hours Strong band

SindashO(asymm stret)includedTindashO(Stret) -800ndash1110 cmminus1

3042

Benchmark 2 Si and little amountof Ti and Mg Epoxy resin Triethylenetetramine

with catalyst 14ndash16 hours 3175

Benchmark 3 Si and littleamount of Ti Epoxy resin Triethylenetetramine

with catalyst 12ndash14 hours 3361

STC1 Zn Ti SiBisphenol A basedepoxy resin with

Zn dust

Fomulatedpolyamidoamine

adduct8ndash10 hours ZnndashO at 454 cmminus1 2992

STC2 Fe Ti SiBisphenol A basedepoxy resin with

MIO flakes

Fomulatedpolyamidoamine

adduct8ndash10 hours FendashO at 560 cmminus1 2920

Table 3 Tests for evaluating uniformity and adhesion properties of the films

Surface conditions SystemsBenchmark 1 Benchmark 2 Benchmark 3 STC1 STC2

Applicability

Moisture No uniform filmformation

No uniform filmformation

No uniform filmformation

Uniform filmformed

Uniform filmformed

Oil contaminatedNo uniform film

formationNo uniform film

formationNo uniform film

formationUniform film

formedUniform film

formed

ST2ST3(properlyprepared)

Uniform filmformed

Uniform filmformed

Uniform filmformed

Uniform filmformed

Uniform filmformed

Pull offadhesion(PSI)

Moist

Not possible as noadhesionuniformfilm formationbecause of highsurface tension

Not possible as noadhesionuniformfilm formationbecause of highsurface tension

Not possible as noadhesionuniformfilm formationbecause of highsurface tension

Tested and foundto be 49 (cohesive

failure

Tested and foundto be 47 (cohesive

failure)

Oil contaminated

Not possible as noadhesionuniformfilm formationbecause of highsurface tension

Not possible as noadhesionuniformfilm formationbecause of highsurface tension

Not possible as noadhesionuniformfilm formation

Tested and foundto be

48MPa (cohesivefailure)

Tested and foundto be 46 (cohesive

failure)

ST2 (thoroughlyprepared)

5MPa(adhesion failure)

54MPa(cohesive failure)

49MPa(adhesion failure)

54MPa (cohesivefailure)

52MPa (cohesivefailure)

oil contaminated surfaces so pull off adhesion test can bedone over these surfaces (passing criteria to be a surfacetolerant coating) All products formuniformfilm on properlyprepared surfaces

3 Results and Discussions

31 Chemical Bonding Analysis by FT-IR Spectroscopy Allspectra were recorded ranging from 3300 to 450 cmminus1 wavenumber by using Magna-IR TM spectrometer 550 (Nicolet)equipped with DTGS detector and averaging of 32 scansChemical bonding between the molecules was character-ized by FT-IR spectra FT-IR spectroscopy is a methodto detect functional groups by transition in vibrationallevel of the molecules like aliphatic CH3 stretching fallsin 2850ndash3000 cmminus1 Absorption peaks of other functional

groups involved in coating systems are shown in Table 4and Figure 4 The presence of the absorption peaks of CH3stretching and CndashN stretching shows that the basic structureof base polymer matrix of STC2 is not changed after theaddition of MIO While in benchmark products there are nosignificant absorption peaks of FendashO and ZnndashO in spectraas shown in Figure 4 and Table 4 which suggest no metallicoxide present in the benchmark coating systems

32 Surface Morphology by SemEdax Analysis Scanningelectron microscopy pictures were taken using Hitachi S-3400N microscope (acceleration voltage 15 kV)

SEM was used to determine the sample surface topogra-phy and to get the idea of the distribution of the pigmentspresent in primer STC1 and primer STC2 EDAX analysiswas used to evaluate elemental composition of the coatingson the surface region SEMmicrographs of primer STC1 and

6 Journal of Coatings

Table 4 Chemical bonding analysis by FT-IR spectroscopy

Wave number (cmminus1) Chemical analysis3000ndash2850 cmminus1 Aliphatic ndashCH2 and CH3 stretching900ndash1250 cmminus1 ndashCndashNstretching shows the reaction of epoxy and aliphatic amine454 cmminus1 ZnndashOstretching vibration Obtained in STC1 only560 cmminus1 FendashOstretching Obtained in STC2 only1000ndash1260 cmminus1 ndashCndashO coupled with CndashC 997904rArr CndashCndashO800ndash1110 cmminus1 Strong band SindashOasymmetric stretching included TindashOStretching

600ndash950 cmminus1 TindashO(stretching) only the bands of some widespread pigments overlapped with several other pigments1600ndash1650 cmminus1 Quadrant Stretching of phenyl ring which shows the presence of epoxy resin1490ndash1540 cmminus1 AromaticradicCndashC which shows the presence of epoxy resin

3000 2500 2000 1500 100060

70

80

90

100

110

STC2STC1

STC2STC1

29211607

14681233

15081451

11761240

999

1013

869 721

661607822

600 550 500 45020

40

60

80

100

560

454

Tran

smitt

ance

()

Tran

smitt

ance

()

Wavenumber (cmminus1) Wavenumber (cmminus1)

(a)

3000 2500 2000 1500 100060

70

80

90

100

110

Tran

smitt

ance

()

Tran

smitt

ance

()

Benchmark 1Benchmark 2Benchmark 3

Benchmark 1Benchmark 2Benchmark 3

29231643

1505

14551507

1239 825

8721008

10131244

1176 825

1028

777

800 769687

600 550 500 45020

40

60

80

100

Wavenumber (cmminus1) Wavenumber (cmminus1)

(b)

Figure 4 Comparative FTIR results of (a) STC1 with STC2 (b) benchmark products

primer STC2 (Figure 5) show the homogenous dispersion ofZn particles MIO flakes and other fillers indicate good com-patibility between resin and filler particles while in otherssome agglomeration of silica particles occur which show theheterogenous dispersion indicating the weak compatibility

between the resin and filler particles This agglomerationof silica particles in benchmark coating generates internalstresses and cracks in coating so they do not provide sufficientcorrosion protection of substrate However this uniformdistribution of Zn and MIO particles reduces the internal

Journal of Coatings 7

(a) (b)

(c) (d)

(e)

Figure 5 SEMmicrographs of samples (a) STC1 (b) STC2 (c) benchmark 1 (d) benchmark 2 and (e) benchmark 3

stresses and cracking and also provides sufficient corrosionand barrier protection EDAX images as shown in Figure 6confirm the high percentage of zinc content (which is notavailable in benchmark coatings) in primer STC1 and pres-ence ofMIO in primer STC2 which are themain constituentsproviding cathodic and barrier protection respectively

33 Mechanical Testing Taber abrasion test (ASTM D4060-10) in this test coated panels (4 in times 4 in) were abraded withthe help of abrasive wheels wheel number CS-17 (Rubber +Al2O3) the wheel was 127mm thick and had an externaldiameter of 519mm A test of 1000 cycles was done toobserve the weight loss in the coating This test method hasbeen useful in evaluating the abrasion resistance of attached

coatings Taber abrasion test showed the wear resistance ofthe coatings As seen from Table 5 it is confirmed that boththe STC1 and STC2 coatings behave as good wear resistancedue to the presence of Zn and MIO flakes comparable toother products which indicate good crosslinking density ofthe primer

Pull off adhesion test (ASTMD4541) this test determineseither the greatest perpendicular force (in tension) that asurface area can bear before a plug of material is detachedor whether the surface remains intact at a prescribed force(passfail) Failure will occur along the weakest plane withinthe system comprised of the test fixture adhesive coatingsystem and substrate and will be exposed by the fracturesurface From Figure 7 and Table 5 it is observed that

8 Journal of Coatings

times102

100

80

60

40

20

0

1 2 3 4 5 6 7 8 9

Zn

Zn Zn

COTi Ti

SiAl Au

(keV)

Full scale counts 9403 Cursor 9972keV23 counts

Sample 4(1) pt3

(a)

times102

0

50

40

30

20

10

1 2 3 4 5 6 7 8 9

C

O

Ti

Ti

SiAl Au

Fe

Fe

Fe

Ca

(keV)

Full scale counts 3321 Cursor 9972keV10 counts

Sample 5(1) pt3

(b)

times102

0

50

40

30

20

10

60

0 2 4 6 8 10

C

O

Ti

TiSi

Al

AuAu FeCa

Mg

(keV)

Full scale counts 4644 Sample 1(1) pt2 Cursor 10221 keV15 counts

(c)

times102

80

60

40

20

0

0 2 4 6 8 10

CO

TiTi

Si

Au AuMg

(keV)

Full scale counts 6673 Sample 2(1) pt2 Cursor 10221 keV10 counts

(d)

times102

80

60

40

20

0

0 2 4 6 8 10

CO

Ti

Ti

Si

Au AuAu

(keV)

Full scale counts 11604

140

120

100

Sample 3(1) pt4 Cursor 10221 keV10 counts

(e)

Figure 6 EDAX images of samples (a) STC1 (b) STC2 (c) benchmark 1 (d) benchmark 2 and (e) benchmark 3

the STC1 and STC2underwent cohesive adhesion failureThisshows that the adhesion of the coatings was better than theother products which experienced adhesion failures

Results show that mechanical interlocking and chemicalinteractions throughout the interface are better in STC1 andSTC2 coatings as compared to other products in whichadhesion strength decreased The adhesion of STC2 is dueto MIO flakes which is oriented parallel to the substrateand reacts well with resin which improves the chemicalbonding between the MIO flakes and the resin This givesimprovement in interfacial strength

Impact resistance test (ASTM D2247) this test methodcovers a procedure for rapidly deforming by impact a coatingfilm and its substrate and for evaluating the effect of suchdeformation It has been observed from Table 5 that theSTC1 and STC2 systems surpassed the maximum height ofimpact and have maximum impact energy Sine both systems(STC1 and STC2) were synthesized by using polyamidoaminehardener (polyamine with a long chain fatty acid) which ishelpful in improving the coating flexibility while in bench-mark products polyamine curatives have been added which

is not sufficient to improving the flexibility of coating systemsbecause of short chain length In case of STC2 the MIOflakes in the coating induces stress relaxation eliminate stresspropagation residual stresses and reduce internal stressesFigure 8 shows the panels of coating systems after impacttest The MIO flakes transform and absorb energy whichprevents crack propagation and growing up when the coatingis subjected to an external stress and it will result in theimprovement of the coating flexibility The improvementof the coating flexibility will lead to improvement in thecohesion between the coating and substrate finally In otherproducts there is no MIO flakes and zinc which may be theresult of their low impact strength in case of benchmarks 1and 3

Contact angle measurement (ASTM D7734) this mea-surement was done by goniometer This test is useful forcharacterizing the wettability of surfaces A low advancingcontact angle value (lt45∘) is indicative of wetting and anglesof 10 to 20∘ are indicative of excellent wetting Water canbe used as a test liquid to establish whether a surfaceis hydrophilic (angle lt45∘) hydrophobic (angle gt90∘) or

Journal of Coatings 9

Benchmark 1

(a)

Benchmark 2

(b)

Benchmark 3

(c)

STC1

(d)

STC2

(e)

Figure 7 Pull off adhesion test images of samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

somewhere in between (angle of 45 to 90∘) All coatings werehydrophilic in nature as their contact angle is less than 90∘For coating to be hydrophobic the contact anglemust be equalto or greater than 90∘ (Table 5 and Figure 9)

Tensile test (ASTM D638) this test method is designedto produce tensile property data for the control and specifi-cation of plastic materials by using ultimate tensile strengthmachine From the tensile strength data shown in Table 5it can be concluded that primer STC1 and primer STC2show the tensile strength 1037MPa and 1058MPa which arehigher as compared to other competitive products This maybe due to better bonding strength between epoxy matrix andthe respective pigments (Zn MIO) When the coating underload the stress is transferred from hard pigment to softerepoxy matrixThese pigments provide the good combinationof strength and toughness to the coating which results ingood tensile strength

Flexibility test (ASTM D522) and scratch resistance(ASTMD7027-13) flexibility test methods cover the determi-nation of the resistance to cracking (flexibility) of attached

organic coatings on substrates when elongated by usingconical mandrel bend testerThe specimen is clamped againsta conical mandrel and is bent around the mandrel by aroller mounted on a hand operated lever The diameter ofthe mandrel at the point where the coating starts to crackcan be determined from a scale marked on the specimenclamp Scratch resistance test method is able to characterizethe scratch resistance of polymers by measuring many signif-icant material parameters Table 5 shows that all the coatingsystems passed the maximum bending angle and scratchresistance test (Table 5)

34 Corrosion Studies

341 Salt Spray Test (ASTM B117) Samples were placed incorrosion-resistant self-supporting polyethylene casing Saltspray test provides a controlled corrosive environment whichhas been utilized to produce relative corrosion resistanceinformation for specimens of metals and coated metalsexposed in a given test chamber The coated panels were

10 Journal of Coatings

Benchmark 1

(a)

Benchmark 2

(b)

Benchmark 3

(c)

STC1

(d)

STC2

(e)

Figure 8 Impact resistance test of coated samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

exposed for 2000 hours in salt spray chamber The saltspray chamber was maintained at 35∘C containing 35NaClsolution Figure 10 shows the coated panels at zero 500 1000and 2000 hours After 500 hours initiation of blistering anddelamination took place in benchmark coatings and numberof blisters increased Increased susceptibility of blistering anddelamination may be due to the increased ionic permeabilityof the coating and the formation of amine carbamate (formedby absorbing carbon dioxide and moisture present in atmo-sphere by polyamine curative) over coating surface which is aclear indication of blushing As a comparison to others STC1provided efficient protective function against delaminationaround scribed areas ensured intense galvanic function of theprimer The other products show significant corrosion nearthe scribed areas large blisters and delamination Table 6summarizes the changes that took place in panels during saltspray exposure

342 Electrochemical Test Electrochemical tests were doneby using an electrochemical analyzer CH 604C from CH

instruments USA A three-electrode glass cell equipped witha platinum counter electrode an AgAgClCl- referenceelectrode with uncoated and coated substrates was used forthe electrochemical measurements Electrochemical mea-surements were performed under extreme environmentalconditions consisting of an aqueous air exposed sodiumchloride 35 NaCl solution at room temperature Eachsamplemasked by paraffin and only left 10 cm2 (10lowast 10) areain the solution The working electrode included an electricalconnection wire which was initially attaching the surface ofsample with conducting glue Samples were allowed to stabi-lize at their open circuit potential (OCP) The corrosion rateof coatings was measured by immersion studies conducted in35 wt NaCl solution at room temperature after 2000 hrs ofsalt spray exposure

343 Electrochemical Polarization Test Potentiodynamicpolarization was performed at 001 Vsec scan rate From thepolarization curves (Figure 11) and the data from Table 6 it is

Journal of Coatings 11

(a) (b)

(c) (d)

(e)

Figure 9 Contact angle test of coated samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

clear that the STC1 has higher OCP and lower current density(29 times 10minus7 A cmminus2) and corrosion rate as compared to MIObased STC2 and other benchmark coatingsThis is due to thepresence of zinc oxide which provides cathodic protection tothe substrate initially

Later due to formation of the corrosion product that isZnO the zinc in the system gets consumed and the formedproduct which provides barrier protection to the substrate Inthe case of STC2 theMIOflakes are responsible for providingbarrier protection but since there is no zinc its corrosion rateis higher than STC1 So it is confirmed that the other productshave higher current densities and corrosion rate than theSTC1 and STC2 due to their lack of cathodic protection as

well as less barrier protection because of the absence of zincand MIO flakes in coating material

344 Durability Test All electrochemical impedance spec-troscopy (EIS) spectra were acquired at the open circuitpotential in a frequency range from 10Hz to 1000Hz withac excitation amplitude of 5mVs in a 35 NaCl solutionat room temperature The durability of the coating systemswas estimated by exposing the samples at zero 500 1000 and2000 hours The pore resistance of the coatings is calculatedby plotting bode plots at respective hours

Initially the STC1 shows excellent barrier protectionowing to the homogenous distribution of zinc particles It has

12 Journal of Coatings

At 500 hours At 1000 hours At 2000 hoursAt 0 hour

(a)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(b)

At 500 hours At 1000 hours At 2000 hoursAt 0 hour

(c)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(d)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(e)

Figure 10 Salt spray images of coated panels at 0 500 1000 and 2000 hours (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1and (e) STC2

been observed that from zero to 500 hours there is decreasein pore resistance from log (Zohm) 65 to 48 this may bedue to initiation of corrosion process due to percolation ofthe electrolyte solution After that from 500 to 2000 hrs thereis not much change in pore resistance due to the consumedzinc that formed the corrosion product as ZnO as shown in

bode plots (Figure 12) This is attributed to filling up of voidspaces of the coatings by corrosion products of Zn whichprovide additional barrier protection In STC2 theMIOplaysa key role for providing barrier protection to the substrateIt provides the permeability allowing the transport of watervapor into and out of the film which is helpful in preventing

Journal of Coatings 13

Table 5 Comparative mechanical test results of different kinds of surface tolerant coatings

Benchmark 1 Benchmark 2 Benchmark 3 STC1 STC2

Pull off adhesion (Mpa) 5Mpa 54Mpa 49Mpa 54Mpa 52MpaAdhesion failure Cohesive failure Adhesion failure Cohesive failure Cohesive failure

Impact energy load4730 kgmax height 2310158401015840

2318 J 2688 J 1854 J 2688 J 2688 J

Scratch resistance 10Kg passed 10Kg passed 10Kg passed 10Kg passed 10Kg passedFlexibility 140∘ passed 140∘ passed 140∘ passed 140∘ passed 140∘ passedTensile strength 846Mpa 576MPA 507MPa 1037MPa 1058MPaTaber abrasion results byweight loss (gm) 01277 00945 02080 00981 01073

Contact angle 5534 5234 6224 7474 6720

Table 6 Comparative corrosion test results of different kinds of surface tolerant coatings

SystemsSalt spray test (SST) Log (119885Ohm) Corrosion rate

(mpy-miles peryear)0ndash500 hours 500ndash1000 hours 1000ndash2000 hours 0 hour 500 hours 1000 hours 2000

hours

Benchmark 1Initiation of

blistering at 300hours

Number ofblisters incresed

Large blisters atthe centre and

edges65 48 38 2 3036mpy

Benchmark 2Initiation of

blistering at 350hours

Number ofblisters incresed

Number ofblisters increased 55 42 33 29 0795mpy

Benchmark 3 No blisteringLarge blisters atthe centre and

edges

Large number ofsmall edges 38 32 3 29 0420mpy

STC1 No blistering No blisteringInitiation of

blistering at 1600hours

75 48 42 41 0133mpy

STC2 No blistering No blisteringInitiation of

blistering at 1500hours

65 55 48 41 0311mpy

blistering and delamination even under severe temperaturegradients From Figure 13 it can be seen that initially theSTC1 shows higher value of coating resistance and the slope isless steep than the STC2The results show that the coatings atthis time were good shielding layers with large impedancesand the matrix was protected well After 500 hrs the poreresistance started decreasing assuming that the electrolytesolution was penetrating through the pores of the coatings(Figure 13 and Table 6) This could be because there was nopath in the coatings that allowed the electrolyte to reach thesubstrate with increasing exposure time The coating layerwas gradually attacked and thinned down by the electrolytewhich led to a decrease in the coating resistance (119877119901) becauseelectrolyte was transported to the metal substrate throughionic conducting paths in the coating The other benchmarkproducts show relatively less coating resistance

4 Conclusions

(1) Zinc dust pigmented surface tolerant coating (STC1)and micaceous iron oxide pigmented surface tolerant

14 12 10 08 06 04 02 00

log

(cur

rent

A)

Potential (V versus Calomel)

Benchmark 1Benchmark 2Benchmark 3

STC1STC2

minus100

minus95

minus90

minus85

minus80

minus75

minus70

minus65

minus60

minus55

minus50

minus45

Figure 11 Comparative Tafel plots of STC1 and 2 and benchmarks1 2 and 3

14 Journal of Coatings

16 20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

9

500 hours1000 hours

2000 hours0 hour

log

(ZO

hm)

log (freqHz)

(a)

20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

log (freqHz)

500 hours1000 hours

0 hour2000 hours

log

(ZO

hm)

(b)

18 21 24 27 30 33 36 39 42 45 4824

26

28

30

32

34

36

38

0 hours500 hours

2000 hours1000 hours

log (freqHz)

log

(ZO

hm)

(c)

16 20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

500 hours2000 hours

0 hour1000 hours

log (freqHz)

log

(ZO

hm)

(d)

20 24 28 32 36 40 44 48 5220

25

30

35

40

45

50

55

60

65

1000 hours2000 hours

500 hours0 hour

log (freqHz)

log

(ZO

hm)

(e)

Figure 12 Bode plots of various coating systems (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

Journal of Coatings 15

0 500 1000 1500 20000

1

2

3

4

5

6

7

8

Time (h)

Benchmark 1Benchmark 2Benchmark 3

STC1STC2

log

(ZO

hm)

Figure 13 Pore resistance with time for various coating systems

coating (STC2) were found to form a uniform coatingfilm over moist oil contaminated and surface pre-pared hot rolled sheets Excellent surface compatibil-ity to wet surface and good interfacial adhesion maybe due to low surface tension (28Nm) of the coatingscompared to competitive coatings (gt30Nm)

(2) The results of impact resistance tensile strength abra-sion resistance scratch resistance flexibility and pulloff adhesion were found superior than other availableproducts

(3) Anticorrosive pigments such as zinc dust (responsiblefor superior cathodic protection because of its lowerreduction potential than iron) and MIO (flaky shapewhich provide torturous path to the penetration ofcorrosive electrolytes) in the system have shown sig-nificant resistance against migration of chloride ionsand water and the free space between the particle andthe resin was less and thus restricted the penetrationof electrolyte through the pores in the coating filmThis is evident for high pore resistance over time in35 wt NaCl solution The rate of corrosion is alsofound 23 times less in 35 wt NaCl as compared tocompetitive products

(4) Marine simulation corrosion test as per ASTM B 117has shown significant delay in blister formation Thisis due to presence of anticorrosive pigments

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank Stanvac-Superon group forproviding funding and IIT Bombay and Tata Steel Industry

for providing research facilities for this work The authorswould like to thank all the Research Associate team also

References

[1] G C Soltz ldquoThe effects of substrate contaminates on the lifeof epoxy coatings in sea waterrdquo NSRP Report 0329 NationalShipbuilding Research Program 1991

[2] S B R Appleman S Boocock R E F Weaver and G CSoltz ldquoEffect of surface contaminates on coating liferdquo USDepartment of Transportation Federal Highway Administra-tion Publication FHWA-RD-91-011 1991

[3] National Steel and Shipbuilding NSRP Report ldquoPower ToolCleaning an alternate for abrasive blastingrdquo 1993

[4] J W Peart Evaluation of Coatings Applied on Less than IdealSurfaces withPeterson builders inc sturgeon bay Wis USA1995

[5] ldquoCuring Agent for Epoxy Resinsrdquo Three Bond Technical News1990

[6] N Rajgopalan and A S Khanna ldquoEffect of nano-ZnO in low-ering yellowing of aliphatic amine cured DGEBA-based epoxycoatings onUV exposurerdquo International Journal of Scientific andResearch vol 3 no 4 2013

[7] H Lee and K Neville Epoxy Resins Their Synthesis and Char-acterization and Curing of Epoxy Resins Their Applications andTechnology McGraw Hill

[8] Z W Wicks F N Jones and S P Pappas ldquoOrganic coatingsscience and technologyrdquo Dyes and Pigments vol 45 pp 85ndash862000

[9] L S Salem ldquoEpoxies for steelrdquo Journal of Protective Coatings andLinings vol 13 pp 77ndash98 1996

[10] M Ebert et al Polymer vol 32 no 3 p 139 1991[11] S Swier G van Assche W Vuchelen and B VanMele ldquoRole of

complex formation in the polymerization kinetics of modifiedepoxy-amine systemsrdquoMacromolecules vol 38 no 6 pp 2281ndash2288 2005

[12] S Shreepathi P Bajaj and B P Mallik ldquoElectrochemical imp-edance spectroscopy investigations of epoxy zinc rich coatingsrole of Zn content on corrosion protection mechanismrdquo Elec-trochimica Acta vol 55 no 18 pp 5129ndash5134 2010

[13] P A Soslashrensen S Kiil K Dam-Johansen and C E WeinellldquoAnticorrosive coatings a reviewrdquo Journal of Coatings Technol-ogy Research vol 6 no 2 pp 135ndash176 2009

[14] A Ruvolo-Filho and M Magaton ldquoEvaluating barrier proper-ties of acrylic polyurethane and aliphatic polyurethane coatingsloaded with micaceous iron oxide or red iron oxiderdquo PolymerPlastics Technology and Engineering vol 48 no 7 pp 682ndash6952009

[15] C Giudice J C Benftez and M M Linares ldquoZinc-rich epoxyprimers based on lamellar zinc dustrdquo Surface Coatings Interna-tional vol 80 no 6 pp 279ndash284 1997

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

6 Journal of Coatings

Table 4 Chemical bonding analysis by FT-IR spectroscopy

Wave number (cmminus1) Chemical analysis3000ndash2850 cmminus1 Aliphatic ndashCH2 and CH3 stretching900ndash1250 cmminus1 ndashCndashNstretching shows the reaction of epoxy and aliphatic amine454 cmminus1 ZnndashOstretching vibration Obtained in STC1 only560 cmminus1 FendashOstretching Obtained in STC2 only1000ndash1260 cmminus1 ndashCndashO coupled with CndashC 997904rArr CndashCndashO800ndash1110 cmminus1 Strong band SindashOasymmetric stretching included TindashOStretching

600ndash950 cmminus1 TindashO(stretching) only the bands of some widespread pigments overlapped with several other pigments1600ndash1650 cmminus1 Quadrant Stretching of phenyl ring which shows the presence of epoxy resin1490ndash1540 cmminus1 AromaticradicCndashC which shows the presence of epoxy resin

3000 2500 2000 1500 100060

70

80

90

100

110

STC2STC1

STC2STC1

29211607

14681233

15081451

11761240

999

1013

869 721

661607822

600 550 500 45020

40

60

80

100

560

454

Tran

smitt

ance

()

Tran

smitt

ance

()

Wavenumber (cmminus1) Wavenumber (cmminus1)

(a)

3000 2500 2000 1500 100060

70

80

90

100

110

Tran

smitt

ance

()

Tran

smitt

ance

()

Benchmark 1Benchmark 2Benchmark 3

Benchmark 1Benchmark 2Benchmark 3

29231643

1505

14551507

1239 825

8721008

10131244

1176 825

1028

777

800 769687

600 550 500 45020

40

60

80

100

Wavenumber (cmminus1) Wavenumber (cmminus1)

(b)

Figure 4 Comparative FTIR results of (a) STC1 with STC2 (b) benchmark products

primer STC2 (Figure 5) show the homogenous dispersion ofZn particles MIO flakes and other fillers indicate good com-patibility between resin and filler particles while in otherssome agglomeration of silica particles occur which show theheterogenous dispersion indicating the weak compatibility

between the resin and filler particles This agglomerationof silica particles in benchmark coating generates internalstresses and cracks in coating so they do not provide sufficientcorrosion protection of substrate However this uniformdistribution of Zn and MIO particles reduces the internal

Journal of Coatings 7

(a) (b)

(c) (d)

(e)

Figure 5 SEMmicrographs of samples (a) STC1 (b) STC2 (c) benchmark 1 (d) benchmark 2 and (e) benchmark 3

stresses and cracking and also provides sufficient corrosionand barrier protection EDAX images as shown in Figure 6confirm the high percentage of zinc content (which is notavailable in benchmark coatings) in primer STC1 and pres-ence ofMIO in primer STC2 which are themain constituentsproviding cathodic and barrier protection respectively

33 Mechanical Testing Taber abrasion test (ASTM D4060-10) in this test coated panels (4 in times 4 in) were abraded withthe help of abrasive wheels wheel number CS-17 (Rubber +Al2O3) the wheel was 127mm thick and had an externaldiameter of 519mm A test of 1000 cycles was done toobserve the weight loss in the coating This test method hasbeen useful in evaluating the abrasion resistance of attached

coatings Taber abrasion test showed the wear resistance ofthe coatings As seen from Table 5 it is confirmed that boththe STC1 and STC2 coatings behave as good wear resistancedue to the presence of Zn and MIO flakes comparable toother products which indicate good crosslinking density ofthe primer

Pull off adhesion test (ASTMD4541) this test determineseither the greatest perpendicular force (in tension) that asurface area can bear before a plug of material is detachedor whether the surface remains intact at a prescribed force(passfail) Failure will occur along the weakest plane withinthe system comprised of the test fixture adhesive coatingsystem and substrate and will be exposed by the fracturesurface From Figure 7 and Table 5 it is observed that

8 Journal of Coatings

times102

100

80

60

40

20

0

1 2 3 4 5 6 7 8 9

Zn

Zn Zn

COTi Ti

SiAl Au

(keV)

Full scale counts 9403 Cursor 9972keV23 counts

Sample 4(1) pt3

(a)

times102

0

50

40

30

20

10

1 2 3 4 5 6 7 8 9

C

O

Ti

Ti

SiAl Au

Fe

Fe

Fe

Ca

(keV)

Full scale counts 3321 Cursor 9972keV10 counts

Sample 5(1) pt3

(b)

times102

0

50

40

30

20

10

60

0 2 4 6 8 10

C

O

Ti

TiSi

Al

AuAu FeCa

Mg

(keV)

Full scale counts 4644 Sample 1(1) pt2 Cursor 10221 keV15 counts

(c)

times102

80

60

40

20

0

0 2 4 6 8 10

CO

TiTi

Si

Au AuMg

(keV)

Full scale counts 6673 Sample 2(1) pt2 Cursor 10221 keV10 counts

(d)

times102

80

60

40

20

0

0 2 4 6 8 10

CO

Ti

Ti

Si

Au AuAu

(keV)

Full scale counts 11604

140

120

100

Sample 3(1) pt4 Cursor 10221 keV10 counts

(e)

Figure 6 EDAX images of samples (a) STC1 (b) STC2 (c) benchmark 1 (d) benchmark 2 and (e) benchmark 3

the STC1 and STC2underwent cohesive adhesion failureThisshows that the adhesion of the coatings was better than theother products which experienced adhesion failures

Results show that mechanical interlocking and chemicalinteractions throughout the interface are better in STC1 andSTC2 coatings as compared to other products in whichadhesion strength decreased The adhesion of STC2 is dueto MIO flakes which is oriented parallel to the substrateand reacts well with resin which improves the chemicalbonding between the MIO flakes and the resin This givesimprovement in interfacial strength

Impact resistance test (ASTM D2247) this test methodcovers a procedure for rapidly deforming by impact a coatingfilm and its substrate and for evaluating the effect of suchdeformation It has been observed from Table 5 that theSTC1 and STC2 systems surpassed the maximum height ofimpact and have maximum impact energy Sine both systems(STC1 and STC2) were synthesized by using polyamidoaminehardener (polyamine with a long chain fatty acid) which ishelpful in improving the coating flexibility while in bench-mark products polyamine curatives have been added which

is not sufficient to improving the flexibility of coating systemsbecause of short chain length In case of STC2 the MIOflakes in the coating induces stress relaxation eliminate stresspropagation residual stresses and reduce internal stressesFigure 8 shows the panels of coating systems after impacttest The MIO flakes transform and absorb energy whichprevents crack propagation and growing up when the coatingis subjected to an external stress and it will result in theimprovement of the coating flexibility The improvementof the coating flexibility will lead to improvement in thecohesion between the coating and substrate finally In otherproducts there is no MIO flakes and zinc which may be theresult of their low impact strength in case of benchmarks 1and 3

Contact angle measurement (ASTM D7734) this mea-surement was done by goniometer This test is useful forcharacterizing the wettability of surfaces A low advancingcontact angle value (lt45∘) is indicative of wetting and anglesof 10 to 20∘ are indicative of excellent wetting Water canbe used as a test liquid to establish whether a surfaceis hydrophilic (angle lt45∘) hydrophobic (angle gt90∘) or

Journal of Coatings 9

Benchmark 1

(a)

Benchmark 2

(b)

Benchmark 3

(c)

STC1

(d)

STC2

(e)

Figure 7 Pull off adhesion test images of samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

somewhere in between (angle of 45 to 90∘) All coatings werehydrophilic in nature as their contact angle is less than 90∘For coating to be hydrophobic the contact anglemust be equalto or greater than 90∘ (Table 5 and Figure 9)

Tensile test (ASTM D638) this test method is designedto produce tensile property data for the control and specifi-cation of plastic materials by using ultimate tensile strengthmachine From the tensile strength data shown in Table 5it can be concluded that primer STC1 and primer STC2show the tensile strength 1037MPa and 1058MPa which arehigher as compared to other competitive products This maybe due to better bonding strength between epoxy matrix andthe respective pigments (Zn MIO) When the coating underload the stress is transferred from hard pigment to softerepoxy matrixThese pigments provide the good combinationof strength and toughness to the coating which results ingood tensile strength

Flexibility test (ASTM D522) and scratch resistance(ASTMD7027-13) flexibility test methods cover the determi-nation of the resistance to cracking (flexibility) of attached

organic coatings on substrates when elongated by usingconical mandrel bend testerThe specimen is clamped againsta conical mandrel and is bent around the mandrel by aroller mounted on a hand operated lever The diameter ofthe mandrel at the point where the coating starts to crackcan be determined from a scale marked on the specimenclamp Scratch resistance test method is able to characterizethe scratch resistance of polymers by measuring many signif-icant material parameters Table 5 shows that all the coatingsystems passed the maximum bending angle and scratchresistance test (Table 5)

34 Corrosion Studies

341 Salt Spray Test (ASTM B117) Samples were placed incorrosion-resistant self-supporting polyethylene casing Saltspray test provides a controlled corrosive environment whichhas been utilized to produce relative corrosion resistanceinformation for specimens of metals and coated metalsexposed in a given test chamber The coated panels were

10 Journal of Coatings

Benchmark 1

(a)

Benchmark 2

(b)

Benchmark 3

(c)

STC1

(d)

STC2

(e)

Figure 8 Impact resistance test of coated samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

exposed for 2000 hours in salt spray chamber The saltspray chamber was maintained at 35∘C containing 35NaClsolution Figure 10 shows the coated panels at zero 500 1000and 2000 hours After 500 hours initiation of blistering anddelamination took place in benchmark coatings and numberof blisters increased Increased susceptibility of blistering anddelamination may be due to the increased ionic permeabilityof the coating and the formation of amine carbamate (formedby absorbing carbon dioxide and moisture present in atmo-sphere by polyamine curative) over coating surface which is aclear indication of blushing As a comparison to others STC1provided efficient protective function against delaminationaround scribed areas ensured intense galvanic function of theprimer The other products show significant corrosion nearthe scribed areas large blisters and delamination Table 6summarizes the changes that took place in panels during saltspray exposure

342 Electrochemical Test Electrochemical tests were doneby using an electrochemical analyzer CH 604C from CH

instruments USA A three-electrode glass cell equipped witha platinum counter electrode an AgAgClCl- referenceelectrode with uncoated and coated substrates was used forthe electrochemical measurements Electrochemical mea-surements were performed under extreme environmentalconditions consisting of an aqueous air exposed sodiumchloride 35 NaCl solution at room temperature Eachsamplemasked by paraffin and only left 10 cm2 (10lowast 10) areain the solution The working electrode included an electricalconnection wire which was initially attaching the surface ofsample with conducting glue Samples were allowed to stabi-lize at their open circuit potential (OCP) The corrosion rateof coatings was measured by immersion studies conducted in35 wt NaCl solution at room temperature after 2000 hrs ofsalt spray exposure

343 Electrochemical Polarization Test Potentiodynamicpolarization was performed at 001 Vsec scan rate From thepolarization curves (Figure 11) and the data from Table 6 it is

Journal of Coatings 11

(a) (b)

(c) (d)

(e)

Figure 9 Contact angle test of coated samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

clear that the STC1 has higher OCP and lower current density(29 times 10minus7 A cmminus2) and corrosion rate as compared to MIObased STC2 and other benchmark coatingsThis is due to thepresence of zinc oxide which provides cathodic protection tothe substrate initially

Later due to formation of the corrosion product that isZnO the zinc in the system gets consumed and the formedproduct which provides barrier protection to the substrate Inthe case of STC2 theMIOflakes are responsible for providingbarrier protection but since there is no zinc its corrosion rateis higher than STC1 So it is confirmed that the other productshave higher current densities and corrosion rate than theSTC1 and STC2 due to their lack of cathodic protection as

well as less barrier protection because of the absence of zincand MIO flakes in coating material

344 Durability Test All electrochemical impedance spec-troscopy (EIS) spectra were acquired at the open circuitpotential in a frequency range from 10Hz to 1000Hz withac excitation amplitude of 5mVs in a 35 NaCl solutionat room temperature The durability of the coating systemswas estimated by exposing the samples at zero 500 1000 and2000 hours The pore resistance of the coatings is calculatedby plotting bode plots at respective hours

Initially the STC1 shows excellent barrier protectionowing to the homogenous distribution of zinc particles It has

12 Journal of Coatings

At 500 hours At 1000 hours At 2000 hoursAt 0 hour

(a)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(b)

At 500 hours At 1000 hours At 2000 hoursAt 0 hour

(c)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(d)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(e)

Figure 10 Salt spray images of coated panels at 0 500 1000 and 2000 hours (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1and (e) STC2

been observed that from zero to 500 hours there is decreasein pore resistance from log (Zohm) 65 to 48 this may bedue to initiation of corrosion process due to percolation ofthe electrolyte solution After that from 500 to 2000 hrs thereis not much change in pore resistance due to the consumedzinc that formed the corrosion product as ZnO as shown in

bode plots (Figure 12) This is attributed to filling up of voidspaces of the coatings by corrosion products of Zn whichprovide additional barrier protection In STC2 theMIOplaysa key role for providing barrier protection to the substrateIt provides the permeability allowing the transport of watervapor into and out of the film which is helpful in preventing

Journal of Coatings 13

Table 5 Comparative mechanical test results of different kinds of surface tolerant coatings

Benchmark 1 Benchmark 2 Benchmark 3 STC1 STC2

Pull off adhesion (Mpa) 5Mpa 54Mpa 49Mpa 54Mpa 52MpaAdhesion failure Cohesive failure Adhesion failure Cohesive failure Cohesive failure

Impact energy load4730 kgmax height 2310158401015840

2318 J 2688 J 1854 J 2688 J 2688 J

Scratch resistance 10Kg passed 10Kg passed 10Kg passed 10Kg passed 10Kg passedFlexibility 140∘ passed 140∘ passed 140∘ passed 140∘ passed 140∘ passedTensile strength 846Mpa 576MPA 507MPa 1037MPa 1058MPaTaber abrasion results byweight loss (gm) 01277 00945 02080 00981 01073

Contact angle 5534 5234 6224 7474 6720

Table 6 Comparative corrosion test results of different kinds of surface tolerant coatings

SystemsSalt spray test (SST) Log (119885Ohm) Corrosion rate

(mpy-miles peryear)0ndash500 hours 500ndash1000 hours 1000ndash2000 hours 0 hour 500 hours 1000 hours 2000

hours

Benchmark 1Initiation of

blistering at 300hours

Number ofblisters incresed

Large blisters atthe centre and

edges65 48 38 2 3036mpy

Benchmark 2Initiation of

blistering at 350hours

Number ofblisters incresed

Number ofblisters increased 55 42 33 29 0795mpy

Benchmark 3 No blisteringLarge blisters atthe centre and

edges

Large number ofsmall edges 38 32 3 29 0420mpy

STC1 No blistering No blisteringInitiation of

blistering at 1600hours

75 48 42 41 0133mpy

STC2 No blistering No blisteringInitiation of

blistering at 1500hours

65 55 48 41 0311mpy

blistering and delamination even under severe temperaturegradients From Figure 13 it can be seen that initially theSTC1 shows higher value of coating resistance and the slope isless steep than the STC2The results show that the coatings atthis time were good shielding layers with large impedancesand the matrix was protected well After 500 hrs the poreresistance started decreasing assuming that the electrolytesolution was penetrating through the pores of the coatings(Figure 13 and Table 6) This could be because there was nopath in the coatings that allowed the electrolyte to reach thesubstrate with increasing exposure time The coating layerwas gradually attacked and thinned down by the electrolytewhich led to a decrease in the coating resistance (119877119901) becauseelectrolyte was transported to the metal substrate throughionic conducting paths in the coating The other benchmarkproducts show relatively less coating resistance

4 Conclusions

(1) Zinc dust pigmented surface tolerant coating (STC1)and micaceous iron oxide pigmented surface tolerant

14 12 10 08 06 04 02 00

log

(cur

rent

A)

Potential (V versus Calomel)

Benchmark 1Benchmark 2Benchmark 3

STC1STC2

minus100

minus95

minus90

minus85

minus80

minus75

minus70

minus65

minus60

minus55

minus50

minus45

Figure 11 Comparative Tafel plots of STC1 and 2 and benchmarks1 2 and 3

14 Journal of Coatings

16 20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

9

500 hours1000 hours

2000 hours0 hour

log

(ZO

hm)

log (freqHz)

(a)

20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

log (freqHz)

500 hours1000 hours

0 hour2000 hours

log

(ZO

hm)

(b)

18 21 24 27 30 33 36 39 42 45 4824

26

28

30

32

34

36

38

0 hours500 hours

2000 hours1000 hours

log (freqHz)

log

(ZO

hm)

(c)

16 20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

500 hours2000 hours

0 hour1000 hours

log (freqHz)

log

(ZO

hm)

(d)

20 24 28 32 36 40 44 48 5220

25

30

35

40

45

50

55

60

65

1000 hours2000 hours

500 hours0 hour

log (freqHz)

log

(ZO

hm)

(e)

Figure 12 Bode plots of various coating systems (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

Journal of Coatings 15

0 500 1000 1500 20000

1

2

3

4

5

6

7

8

Time (h)

Benchmark 1Benchmark 2Benchmark 3

STC1STC2

log

(ZO

hm)

Figure 13 Pore resistance with time for various coating systems

coating (STC2) were found to form a uniform coatingfilm over moist oil contaminated and surface pre-pared hot rolled sheets Excellent surface compatibil-ity to wet surface and good interfacial adhesion maybe due to low surface tension (28Nm) of the coatingscompared to competitive coatings (gt30Nm)

(2) The results of impact resistance tensile strength abra-sion resistance scratch resistance flexibility and pulloff adhesion were found superior than other availableproducts

(3) Anticorrosive pigments such as zinc dust (responsiblefor superior cathodic protection because of its lowerreduction potential than iron) and MIO (flaky shapewhich provide torturous path to the penetration ofcorrosive electrolytes) in the system have shown sig-nificant resistance against migration of chloride ionsand water and the free space between the particle andthe resin was less and thus restricted the penetrationof electrolyte through the pores in the coating filmThis is evident for high pore resistance over time in35 wt NaCl solution The rate of corrosion is alsofound 23 times less in 35 wt NaCl as compared tocompetitive products

(4) Marine simulation corrosion test as per ASTM B 117has shown significant delay in blister formation Thisis due to presence of anticorrosive pigments

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank Stanvac-Superon group forproviding funding and IIT Bombay and Tata Steel Industry

for providing research facilities for this work The authorswould like to thank all the Research Associate team also

References

[1] G C Soltz ldquoThe effects of substrate contaminates on the lifeof epoxy coatings in sea waterrdquo NSRP Report 0329 NationalShipbuilding Research Program 1991

[2] S B R Appleman S Boocock R E F Weaver and G CSoltz ldquoEffect of surface contaminates on coating liferdquo USDepartment of Transportation Federal Highway Administra-tion Publication FHWA-RD-91-011 1991

[3] National Steel and Shipbuilding NSRP Report ldquoPower ToolCleaning an alternate for abrasive blastingrdquo 1993

[4] J W Peart Evaluation of Coatings Applied on Less than IdealSurfaces withPeterson builders inc sturgeon bay Wis USA1995

[5] ldquoCuring Agent for Epoxy Resinsrdquo Three Bond Technical News1990

[6] N Rajgopalan and A S Khanna ldquoEffect of nano-ZnO in low-ering yellowing of aliphatic amine cured DGEBA-based epoxycoatings onUV exposurerdquo International Journal of Scientific andResearch vol 3 no 4 2013

[7] H Lee and K Neville Epoxy Resins Their Synthesis and Char-acterization and Curing of Epoxy Resins Their Applications andTechnology McGraw Hill

[8] Z W Wicks F N Jones and S P Pappas ldquoOrganic coatingsscience and technologyrdquo Dyes and Pigments vol 45 pp 85ndash862000

[9] L S Salem ldquoEpoxies for steelrdquo Journal of Protective Coatings andLinings vol 13 pp 77ndash98 1996

[10] M Ebert et al Polymer vol 32 no 3 p 139 1991[11] S Swier G van Assche W Vuchelen and B VanMele ldquoRole of

complex formation in the polymerization kinetics of modifiedepoxy-amine systemsrdquoMacromolecules vol 38 no 6 pp 2281ndash2288 2005

[12] S Shreepathi P Bajaj and B P Mallik ldquoElectrochemical imp-edance spectroscopy investigations of epoxy zinc rich coatingsrole of Zn content on corrosion protection mechanismrdquo Elec-trochimica Acta vol 55 no 18 pp 5129ndash5134 2010

[13] P A Soslashrensen S Kiil K Dam-Johansen and C E WeinellldquoAnticorrosive coatings a reviewrdquo Journal of Coatings Technol-ogy Research vol 6 no 2 pp 135ndash176 2009

[14] A Ruvolo-Filho and M Magaton ldquoEvaluating barrier proper-ties of acrylic polyurethane and aliphatic polyurethane coatingsloaded with micaceous iron oxide or red iron oxiderdquo PolymerPlastics Technology and Engineering vol 48 no 7 pp 682ndash6952009

[15] C Giudice J C Benftez and M M Linares ldquoZinc-rich epoxyprimers based on lamellar zinc dustrdquo Surface Coatings Interna-tional vol 80 no 6 pp 279ndash284 1997

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Journal of Coatings 7

(a) (b)

(c) (d)

(e)

Figure 5 SEMmicrographs of samples (a) STC1 (b) STC2 (c) benchmark 1 (d) benchmark 2 and (e) benchmark 3

stresses and cracking and also provides sufficient corrosionand barrier protection EDAX images as shown in Figure 6confirm the high percentage of zinc content (which is notavailable in benchmark coatings) in primer STC1 and pres-ence ofMIO in primer STC2 which are themain constituentsproviding cathodic and barrier protection respectively

33 Mechanical Testing Taber abrasion test (ASTM D4060-10) in this test coated panels (4 in times 4 in) were abraded withthe help of abrasive wheels wheel number CS-17 (Rubber +Al2O3) the wheel was 127mm thick and had an externaldiameter of 519mm A test of 1000 cycles was done toobserve the weight loss in the coating This test method hasbeen useful in evaluating the abrasion resistance of attached

coatings Taber abrasion test showed the wear resistance ofthe coatings As seen from Table 5 it is confirmed that boththe STC1 and STC2 coatings behave as good wear resistancedue to the presence of Zn and MIO flakes comparable toother products which indicate good crosslinking density ofthe primer

Pull off adhesion test (ASTMD4541) this test determineseither the greatest perpendicular force (in tension) that asurface area can bear before a plug of material is detachedor whether the surface remains intact at a prescribed force(passfail) Failure will occur along the weakest plane withinthe system comprised of the test fixture adhesive coatingsystem and substrate and will be exposed by the fracturesurface From Figure 7 and Table 5 it is observed that

8 Journal of Coatings

times102

100

80

60

40

20

0

1 2 3 4 5 6 7 8 9

Zn

Zn Zn

COTi Ti

SiAl Au

(keV)

Full scale counts 9403 Cursor 9972keV23 counts

Sample 4(1) pt3

(a)

times102

0

50

40

30

20

10

1 2 3 4 5 6 7 8 9

C

O

Ti

Ti

SiAl Au

Fe

Fe

Fe

Ca

(keV)

Full scale counts 3321 Cursor 9972keV10 counts

Sample 5(1) pt3

(b)

times102

0

50

40

30

20

10

60

0 2 4 6 8 10

C

O

Ti

TiSi

Al

AuAu FeCa

Mg

(keV)

Full scale counts 4644 Sample 1(1) pt2 Cursor 10221 keV15 counts

(c)

times102

80

60

40

20

0

0 2 4 6 8 10

CO

TiTi

Si

Au AuMg

(keV)

Full scale counts 6673 Sample 2(1) pt2 Cursor 10221 keV10 counts

(d)

times102

80

60

40

20

0

0 2 4 6 8 10

CO

Ti

Ti

Si

Au AuAu

(keV)

Full scale counts 11604

140

120

100

Sample 3(1) pt4 Cursor 10221 keV10 counts

(e)

Figure 6 EDAX images of samples (a) STC1 (b) STC2 (c) benchmark 1 (d) benchmark 2 and (e) benchmark 3

the STC1 and STC2underwent cohesive adhesion failureThisshows that the adhesion of the coatings was better than theother products which experienced adhesion failures

Results show that mechanical interlocking and chemicalinteractions throughout the interface are better in STC1 andSTC2 coatings as compared to other products in whichadhesion strength decreased The adhesion of STC2 is dueto MIO flakes which is oriented parallel to the substrateand reacts well with resin which improves the chemicalbonding between the MIO flakes and the resin This givesimprovement in interfacial strength

Impact resistance test (ASTM D2247) this test methodcovers a procedure for rapidly deforming by impact a coatingfilm and its substrate and for evaluating the effect of suchdeformation It has been observed from Table 5 that theSTC1 and STC2 systems surpassed the maximum height ofimpact and have maximum impact energy Sine both systems(STC1 and STC2) were synthesized by using polyamidoaminehardener (polyamine with a long chain fatty acid) which ishelpful in improving the coating flexibility while in bench-mark products polyamine curatives have been added which

is not sufficient to improving the flexibility of coating systemsbecause of short chain length In case of STC2 the MIOflakes in the coating induces stress relaxation eliminate stresspropagation residual stresses and reduce internal stressesFigure 8 shows the panels of coating systems after impacttest The MIO flakes transform and absorb energy whichprevents crack propagation and growing up when the coatingis subjected to an external stress and it will result in theimprovement of the coating flexibility The improvementof the coating flexibility will lead to improvement in thecohesion between the coating and substrate finally In otherproducts there is no MIO flakes and zinc which may be theresult of their low impact strength in case of benchmarks 1and 3

Contact angle measurement (ASTM D7734) this mea-surement was done by goniometer This test is useful forcharacterizing the wettability of surfaces A low advancingcontact angle value (lt45∘) is indicative of wetting and anglesof 10 to 20∘ are indicative of excellent wetting Water canbe used as a test liquid to establish whether a surfaceis hydrophilic (angle lt45∘) hydrophobic (angle gt90∘) or

Journal of Coatings 9

Benchmark 1

(a)

Benchmark 2

(b)

Benchmark 3

(c)

STC1

(d)

STC2

(e)

Figure 7 Pull off adhesion test images of samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

somewhere in between (angle of 45 to 90∘) All coatings werehydrophilic in nature as their contact angle is less than 90∘For coating to be hydrophobic the contact anglemust be equalto or greater than 90∘ (Table 5 and Figure 9)

Tensile test (ASTM D638) this test method is designedto produce tensile property data for the control and specifi-cation of plastic materials by using ultimate tensile strengthmachine From the tensile strength data shown in Table 5it can be concluded that primer STC1 and primer STC2show the tensile strength 1037MPa and 1058MPa which arehigher as compared to other competitive products This maybe due to better bonding strength between epoxy matrix andthe respective pigments (Zn MIO) When the coating underload the stress is transferred from hard pigment to softerepoxy matrixThese pigments provide the good combinationof strength and toughness to the coating which results ingood tensile strength

Flexibility test (ASTM D522) and scratch resistance(ASTMD7027-13) flexibility test methods cover the determi-nation of the resistance to cracking (flexibility) of attached

organic coatings on substrates when elongated by usingconical mandrel bend testerThe specimen is clamped againsta conical mandrel and is bent around the mandrel by aroller mounted on a hand operated lever The diameter ofthe mandrel at the point where the coating starts to crackcan be determined from a scale marked on the specimenclamp Scratch resistance test method is able to characterizethe scratch resistance of polymers by measuring many signif-icant material parameters Table 5 shows that all the coatingsystems passed the maximum bending angle and scratchresistance test (Table 5)

34 Corrosion Studies

341 Salt Spray Test (ASTM B117) Samples were placed incorrosion-resistant self-supporting polyethylene casing Saltspray test provides a controlled corrosive environment whichhas been utilized to produce relative corrosion resistanceinformation for specimens of metals and coated metalsexposed in a given test chamber The coated panels were

10 Journal of Coatings

Benchmark 1

(a)

Benchmark 2

(b)

Benchmark 3

(c)

STC1

(d)

STC2

(e)

Figure 8 Impact resistance test of coated samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

exposed for 2000 hours in salt spray chamber The saltspray chamber was maintained at 35∘C containing 35NaClsolution Figure 10 shows the coated panels at zero 500 1000and 2000 hours After 500 hours initiation of blistering anddelamination took place in benchmark coatings and numberof blisters increased Increased susceptibility of blistering anddelamination may be due to the increased ionic permeabilityof the coating and the formation of amine carbamate (formedby absorbing carbon dioxide and moisture present in atmo-sphere by polyamine curative) over coating surface which is aclear indication of blushing As a comparison to others STC1provided efficient protective function against delaminationaround scribed areas ensured intense galvanic function of theprimer The other products show significant corrosion nearthe scribed areas large blisters and delamination Table 6summarizes the changes that took place in panels during saltspray exposure

342 Electrochemical Test Electrochemical tests were doneby using an electrochemical analyzer CH 604C from CH

instruments USA A three-electrode glass cell equipped witha platinum counter electrode an AgAgClCl- referenceelectrode with uncoated and coated substrates was used forthe electrochemical measurements Electrochemical mea-surements were performed under extreme environmentalconditions consisting of an aqueous air exposed sodiumchloride 35 NaCl solution at room temperature Eachsamplemasked by paraffin and only left 10 cm2 (10lowast 10) areain the solution The working electrode included an electricalconnection wire which was initially attaching the surface ofsample with conducting glue Samples were allowed to stabi-lize at their open circuit potential (OCP) The corrosion rateof coatings was measured by immersion studies conducted in35 wt NaCl solution at room temperature after 2000 hrs ofsalt spray exposure

343 Electrochemical Polarization Test Potentiodynamicpolarization was performed at 001 Vsec scan rate From thepolarization curves (Figure 11) and the data from Table 6 it is

Journal of Coatings 11

(a) (b)

(c) (d)

(e)

Figure 9 Contact angle test of coated samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

clear that the STC1 has higher OCP and lower current density(29 times 10minus7 A cmminus2) and corrosion rate as compared to MIObased STC2 and other benchmark coatingsThis is due to thepresence of zinc oxide which provides cathodic protection tothe substrate initially

Later due to formation of the corrosion product that isZnO the zinc in the system gets consumed and the formedproduct which provides barrier protection to the substrate Inthe case of STC2 theMIOflakes are responsible for providingbarrier protection but since there is no zinc its corrosion rateis higher than STC1 So it is confirmed that the other productshave higher current densities and corrosion rate than theSTC1 and STC2 due to their lack of cathodic protection as

well as less barrier protection because of the absence of zincand MIO flakes in coating material

344 Durability Test All electrochemical impedance spec-troscopy (EIS) spectra were acquired at the open circuitpotential in a frequency range from 10Hz to 1000Hz withac excitation amplitude of 5mVs in a 35 NaCl solutionat room temperature The durability of the coating systemswas estimated by exposing the samples at zero 500 1000 and2000 hours The pore resistance of the coatings is calculatedby plotting bode plots at respective hours

Initially the STC1 shows excellent barrier protectionowing to the homogenous distribution of zinc particles It has

12 Journal of Coatings

At 500 hours At 1000 hours At 2000 hoursAt 0 hour

(a)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(b)

At 500 hours At 1000 hours At 2000 hoursAt 0 hour

(c)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(d)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(e)

Figure 10 Salt spray images of coated panels at 0 500 1000 and 2000 hours (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1and (e) STC2

been observed that from zero to 500 hours there is decreasein pore resistance from log (Zohm) 65 to 48 this may bedue to initiation of corrosion process due to percolation ofthe electrolyte solution After that from 500 to 2000 hrs thereis not much change in pore resistance due to the consumedzinc that formed the corrosion product as ZnO as shown in

bode plots (Figure 12) This is attributed to filling up of voidspaces of the coatings by corrosion products of Zn whichprovide additional barrier protection In STC2 theMIOplaysa key role for providing barrier protection to the substrateIt provides the permeability allowing the transport of watervapor into and out of the film which is helpful in preventing

Journal of Coatings 13

Table 5 Comparative mechanical test results of different kinds of surface tolerant coatings

Benchmark 1 Benchmark 2 Benchmark 3 STC1 STC2

Pull off adhesion (Mpa) 5Mpa 54Mpa 49Mpa 54Mpa 52MpaAdhesion failure Cohesive failure Adhesion failure Cohesive failure Cohesive failure

Impact energy load4730 kgmax height 2310158401015840

2318 J 2688 J 1854 J 2688 J 2688 J

Scratch resistance 10Kg passed 10Kg passed 10Kg passed 10Kg passed 10Kg passedFlexibility 140∘ passed 140∘ passed 140∘ passed 140∘ passed 140∘ passedTensile strength 846Mpa 576MPA 507MPa 1037MPa 1058MPaTaber abrasion results byweight loss (gm) 01277 00945 02080 00981 01073

Contact angle 5534 5234 6224 7474 6720

Table 6 Comparative corrosion test results of different kinds of surface tolerant coatings

SystemsSalt spray test (SST) Log (119885Ohm) Corrosion rate

(mpy-miles peryear)0ndash500 hours 500ndash1000 hours 1000ndash2000 hours 0 hour 500 hours 1000 hours 2000

hours

Benchmark 1Initiation of

blistering at 300hours

Number ofblisters incresed

Large blisters atthe centre and

edges65 48 38 2 3036mpy

Benchmark 2Initiation of

blistering at 350hours

Number ofblisters incresed

Number ofblisters increased 55 42 33 29 0795mpy

Benchmark 3 No blisteringLarge blisters atthe centre and

edges

Large number ofsmall edges 38 32 3 29 0420mpy

STC1 No blistering No blisteringInitiation of

blistering at 1600hours

75 48 42 41 0133mpy

STC2 No blistering No blisteringInitiation of

blistering at 1500hours

65 55 48 41 0311mpy

blistering and delamination even under severe temperaturegradients From Figure 13 it can be seen that initially theSTC1 shows higher value of coating resistance and the slope isless steep than the STC2The results show that the coatings atthis time were good shielding layers with large impedancesand the matrix was protected well After 500 hrs the poreresistance started decreasing assuming that the electrolytesolution was penetrating through the pores of the coatings(Figure 13 and Table 6) This could be because there was nopath in the coatings that allowed the electrolyte to reach thesubstrate with increasing exposure time The coating layerwas gradually attacked and thinned down by the electrolytewhich led to a decrease in the coating resistance (119877119901) becauseelectrolyte was transported to the metal substrate throughionic conducting paths in the coating The other benchmarkproducts show relatively less coating resistance

4 Conclusions

(1) Zinc dust pigmented surface tolerant coating (STC1)and micaceous iron oxide pigmented surface tolerant

14 12 10 08 06 04 02 00

log

(cur

rent

A)

Potential (V versus Calomel)

Benchmark 1Benchmark 2Benchmark 3

STC1STC2

minus100

minus95

minus90

minus85

minus80

minus75

minus70

minus65

minus60

minus55

minus50

minus45

Figure 11 Comparative Tafel plots of STC1 and 2 and benchmarks1 2 and 3

14 Journal of Coatings

16 20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

9

500 hours1000 hours

2000 hours0 hour

log

(ZO

hm)

log (freqHz)

(a)

20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

log (freqHz)

500 hours1000 hours

0 hour2000 hours

log

(ZO

hm)

(b)

18 21 24 27 30 33 36 39 42 45 4824

26

28

30

32

34

36

38

0 hours500 hours

2000 hours1000 hours

log (freqHz)

log

(ZO

hm)

(c)

16 20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

500 hours2000 hours

0 hour1000 hours

log (freqHz)

log

(ZO

hm)

(d)

20 24 28 32 36 40 44 48 5220

25

30

35

40

45

50

55

60

65

1000 hours2000 hours

500 hours0 hour

log (freqHz)

log

(ZO

hm)

(e)

Figure 12 Bode plots of various coating systems (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

Journal of Coatings 15

0 500 1000 1500 20000

1

2

3

4

5

6

7

8

Time (h)

Benchmark 1Benchmark 2Benchmark 3

STC1STC2

log

(ZO

hm)

Figure 13 Pore resistance with time for various coating systems

coating (STC2) were found to form a uniform coatingfilm over moist oil contaminated and surface pre-pared hot rolled sheets Excellent surface compatibil-ity to wet surface and good interfacial adhesion maybe due to low surface tension (28Nm) of the coatingscompared to competitive coatings (gt30Nm)

(2) The results of impact resistance tensile strength abra-sion resistance scratch resistance flexibility and pulloff adhesion were found superior than other availableproducts

(3) Anticorrosive pigments such as zinc dust (responsiblefor superior cathodic protection because of its lowerreduction potential than iron) and MIO (flaky shapewhich provide torturous path to the penetration ofcorrosive electrolytes) in the system have shown sig-nificant resistance against migration of chloride ionsand water and the free space between the particle andthe resin was less and thus restricted the penetrationof electrolyte through the pores in the coating filmThis is evident for high pore resistance over time in35 wt NaCl solution The rate of corrosion is alsofound 23 times less in 35 wt NaCl as compared tocompetitive products

(4) Marine simulation corrosion test as per ASTM B 117has shown significant delay in blister formation Thisis due to presence of anticorrosive pigments

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank Stanvac-Superon group forproviding funding and IIT Bombay and Tata Steel Industry

for providing research facilities for this work The authorswould like to thank all the Research Associate team also

References

[1] G C Soltz ldquoThe effects of substrate contaminates on the lifeof epoxy coatings in sea waterrdquo NSRP Report 0329 NationalShipbuilding Research Program 1991

[2] S B R Appleman S Boocock R E F Weaver and G CSoltz ldquoEffect of surface contaminates on coating liferdquo USDepartment of Transportation Federal Highway Administra-tion Publication FHWA-RD-91-011 1991

[3] National Steel and Shipbuilding NSRP Report ldquoPower ToolCleaning an alternate for abrasive blastingrdquo 1993

[4] J W Peart Evaluation of Coatings Applied on Less than IdealSurfaces withPeterson builders inc sturgeon bay Wis USA1995

[5] ldquoCuring Agent for Epoxy Resinsrdquo Three Bond Technical News1990

[6] N Rajgopalan and A S Khanna ldquoEffect of nano-ZnO in low-ering yellowing of aliphatic amine cured DGEBA-based epoxycoatings onUV exposurerdquo International Journal of Scientific andResearch vol 3 no 4 2013

[7] H Lee and K Neville Epoxy Resins Their Synthesis and Char-acterization and Curing of Epoxy Resins Their Applications andTechnology McGraw Hill

[8] Z W Wicks F N Jones and S P Pappas ldquoOrganic coatingsscience and technologyrdquo Dyes and Pigments vol 45 pp 85ndash862000

[9] L S Salem ldquoEpoxies for steelrdquo Journal of Protective Coatings andLinings vol 13 pp 77ndash98 1996

[10] M Ebert et al Polymer vol 32 no 3 p 139 1991[11] S Swier G van Assche W Vuchelen and B VanMele ldquoRole of

complex formation in the polymerization kinetics of modifiedepoxy-amine systemsrdquoMacromolecules vol 38 no 6 pp 2281ndash2288 2005

[12] S Shreepathi P Bajaj and B P Mallik ldquoElectrochemical imp-edance spectroscopy investigations of epoxy zinc rich coatingsrole of Zn content on corrosion protection mechanismrdquo Elec-trochimica Acta vol 55 no 18 pp 5129ndash5134 2010

[13] P A Soslashrensen S Kiil K Dam-Johansen and C E WeinellldquoAnticorrosive coatings a reviewrdquo Journal of Coatings Technol-ogy Research vol 6 no 2 pp 135ndash176 2009

[14] A Ruvolo-Filho and M Magaton ldquoEvaluating barrier proper-ties of acrylic polyurethane and aliphatic polyurethane coatingsloaded with micaceous iron oxide or red iron oxiderdquo PolymerPlastics Technology and Engineering vol 48 no 7 pp 682ndash6952009

[15] C Giudice J C Benftez and M M Linares ldquoZinc-rich epoxyprimers based on lamellar zinc dustrdquo Surface Coatings Interna-tional vol 80 no 6 pp 279ndash284 1997

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

8 Journal of Coatings

times102

100

80

60

40

20

0

1 2 3 4 5 6 7 8 9

Zn

Zn Zn

COTi Ti

SiAl Au

(keV)

Full scale counts 9403 Cursor 9972keV23 counts

Sample 4(1) pt3

(a)

times102

0

50

40

30

20

10

1 2 3 4 5 6 7 8 9

C

O

Ti

Ti

SiAl Au

Fe

Fe

Fe

Ca

(keV)

Full scale counts 3321 Cursor 9972keV10 counts

Sample 5(1) pt3

(b)

times102

0

50

40

30

20

10

60

0 2 4 6 8 10

C

O

Ti

TiSi

Al

AuAu FeCa

Mg

(keV)

Full scale counts 4644 Sample 1(1) pt2 Cursor 10221 keV15 counts

(c)

times102

80

60

40

20

0

0 2 4 6 8 10

CO

TiTi

Si

Au AuMg

(keV)

Full scale counts 6673 Sample 2(1) pt2 Cursor 10221 keV10 counts

(d)

times102

80

60

40

20

0

0 2 4 6 8 10

CO

Ti

Ti

Si

Au AuAu

(keV)

Full scale counts 11604

140

120

100

Sample 3(1) pt4 Cursor 10221 keV10 counts

(e)

Figure 6 EDAX images of samples (a) STC1 (b) STC2 (c) benchmark 1 (d) benchmark 2 and (e) benchmark 3

the STC1 and STC2underwent cohesive adhesion failureThisshows that the adhesion of the coatings was better than theother products which experienced adhesion failures

Results show that mechanical interlocking and chemicalinteractions throughout the interface are better in STC1 andSTC2 coatings as compared to other products in whichadhesion strength decreased The adhesion of STC2 is dueto MIO flakes which is oriented parallel to the substrateand reacts well with resin which improves the chemicalbonding between the MIO flakes and the resin This givesimprovement in interfacial strength

Impact resistance test (ASTM D2247) this test methodcovers a procedure for rapidly deforming by impact a coatingfilm and its substrate and for evaluating the effect of suchdeformation It has been observed from Table 5 that theSTC1 and STC2 systems surpassed the maximum height ofimpact and have maximum impact energy Sine both systems(STC1 and STC2) were synthesized by using polyamidoaminehardener (polyamine with a long chain fatty acid) which ishelpful in improving the coating flexibility while in bench-mark products polyamine curatives have been added which

is not sufficient to improving the flexibility of coating systemsbecause of short chain length In case of STC2 the MIOflakes in the coating induces stress relaxation eliminate stresspropagation residual stresses and reduce internal stressesFigure 8 shows the panels of coating systems after impacttest The MIO flakes transform and absorb energy whichprevents crack propagation and growing up when the coatingis subjected to an external stress and it will result in theimprovement of the coating flexibility The improvementof the coating flexibility will lead to improvement in thecohesion between the coating and substrate finally In otherproducts there is no MIO flakes and zinc which may be theresult of their low impact strength in case of benchmarks 1and 3

Contact angle measurement (ASTM D7734) this mea-surement was done by goniometer This test is useful forcharacterizing the wettability of surfaces A low advancingcontact angle value (lt45∘) is indicative of wetting and anglesof 10 to 20∘ are indicative of excellent wetting Water canbe used as a test liquid to establish whether a surfaceis hydrophilic (angle lt45∘) hydrophobic (angle gt90∘) or

Journal of Coatings 9

Benchmark 1

(a)

Benchmark 2

(b)

Benchmark 3

(c)

STC1

(d)

STC2

(e)

Figure 7 Pull off adhesion test images of samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

somewhere in between (angle of 45 to 90∘) All coatings werehydrophilic in nature as their contact angle is less than 90∘For coating to be hydrophobic the contact anglemust be equalto or greater than 90∘ (Table 5 and Figure 9)

Tensile test (ASTM D638) this test method is designedto produce tensile property data for the control and specifi-cation of plastic materials by using ultimate tensile strengthmachine From the tensile strength data shown in Table 5it can be concluded that primer STC1 and primer STC2show the tensile strength 1037MPa and 1058MPa which arehigher as compared to other competitive products This maybe due to better bonding strength between epoxy matrix andthe respective pigments (Zn MIO) When the coating underload the stress is transferred from hard pigment to softerepoxy matrixThese pigments provide the good combinationof strength and toughness to the coating which results ingood tensile strength

Flexibility test (ASTM D522) and scratch resistance(ASTMD7027-13) flexibility test methods cover the determi-nation of the resistance to cracking (flexibility) of attached

organic coatings on substrates when elongated by usingconical mandrel bend testerThe specimen is clamped againsta conical mandrel and is bent around the mandrel by aroller mounted on a hand operated lever The diameter ofthe mandrel at the point where the coating starts to crackcan be determined from a scale marked on the specimenclamp Scratch resistance test method is able to characterizethe scratch resistance of polymers by measuring many signif-icant material parameters Table 5 shows that all the coatingsystems passed the maximum bending angle and scratchresistance test (Table 5)

34 Corrosion Studies

341 Salt Spray Test (ASTM B117) Samples were placed incorrosion-resistant self-supporting polyethylene casing Saltspray test provides a controlled corrosive environment whichhas been utilized to produce relative corrosion resistanceinformation for specimens of metals and coated metalsexposed in a given test chamber The coated panels were

10 Journal of Coatings

Benchmark 1

(a)

Benchmark 2

(b)

Benchmark 3

(c)

STC1

(d)

STC2

(e)

Figure 8 Impact resistance test of coated samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

exposed for 2000 hours in salt spray chamber The saltspray chamber was maintained at 35∘C containing 35NaClsolution Figure 10 shows the coated panels at zero 500 1000and 2000 hours After 500 hours initiation of blistering anddelamination took place in benchmark coatings and numberof blisters increased Increased susceptibility of blistering anddelamination may be due to the increased ionic permeabilityof the coating and the formation of amine carbamate (formedby absorbing carbon dioxide and moisture present in atmo-sphere by polyamine curative) over coating surface which is aclear indication of blushing As a comparison to others STC1provided efficient protective function against delaminationaround scribed areas ensured intense galvanic function of theprimer The other products show significant corrosion nearthe scribed areas large blisters and delamination Table 6summarizes the changes that took place in panels during saltspray exposure

342 Electrochemical Test Electrochemical tests were doneby using an electrochemical analyzer CH 604C from CH

instruments USA A three-electrode glass cell equipped witha platinum counter electrode an AgAgClCl- referenceelectrode with uncoated and coated substrates was used forthe electrochemical measurements Electrochemical mea-surements were performed under extreme environmentalconditions consisting of an aqueous air exposed sodiumchloride 35 NaCl solution at room temperature Eachsamplemasked by paraffin and only left 10 cm2 (10lowast 10) areain the solution The working electrode included an electricalconnection wire which was initially attaching the surface ofsample with conducting glue Samples were allowed to stabi-lize at their open circuit potential (OCP) The corrosion rateof coatings was measured by immersion studies conducted in35 wt NaCl solution at room temperature after 2000 hrs ofsalt spray exposure

343 Electrochemical Polarization Test Potentiodynamicpolarization was performed at 001 Vsec scan rate From thepolarization curves (Figure 11) and the data from Table 6 it is

Journal of Coatings 11

(a) (b)

(c) (d)

(e)

Figure 9 Contact angle test of coated samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

clear that the STC1 has higher OCP and lower current density(29 times 10minus7 A cmminus2) and corrosion rate as compared to MIObased STC2 and other benchmark coatingsThis is due to thepresence of zinc oxide which provides cathodic protection tothe substrate initially

Later due to formation of the corrosion product that isZnO the zinc in the system gets consumed and the formedproduct which provides barrier protection to the substrate Inthe case of STC2 theMIOflakes are responsible for providingbarrier protection but since there is no zinc its corrosion rateis higher than STC1 So it is confirmed that the other productshave higher current densities and corrosion rate than theSTC1 and STC2 due to their lack of cathodic protection as

well as less barrier protection because of the absence of zincand MIO flakes in coating material

344 Durability Test All electrochemical impedance spec-troscopy (EIS) spectra were acquired at the open circuitpotential in a frequency range from 10Hz to 1000Hz withac excitation amplitude of 5mVs in a 35 NaCl solutionat room temperature The durability of the coating systemswas estimated by exposing the samples at zero 500 1000 and2000 hours The pore resistance of the coatings is calculatedby plotting bode plots at respective hours

Initially the STC1 shows excellent barrier protectionowing to the homogenous distribution of zinc particles It has

12 Journal of Coatings

At 500 hours At 1000 hours At 2000 hoursAt 0 hour

(a)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(b)

At 500 hours At 1000 hours At 2000 hoursAt 0 hour

(c)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(d)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(e)

Figure 10 Salt spray images of coated panels at 0 500 1000 and 2000 hours (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1and (e) STC2

been observed that from zero to 500 hours there is decreasein pore resistance from log (Zohm) 65 to 48 this may bedue to initiation of corrosion process due to percolation ofthe electrolyte solution After that from 500 to 2000 hrs thereis not much change in pore resistance due to the consumedzinc that formed the corrosion product as ZnO as shown in

bode plots (Figure 12) This is attributed to filling up of voidspaces of the coatings by corrosion products of Zn whichprovide additional barrier protection In STC2 theMIOplaysa key role for providing barrier protection to the substrateIt provides the permeability allowing the transport of watervapor into and out of the film which is helpful in preventing

Journal of Coatings 13

Table 5 Comparative mechanical test results of different kinds of surface tolerant coatings

Benchmark 1 Benchmark 2 Benchmark 3 STC1 STC2

Pull off adhesion (Mpa) 5Mpa 54Mpa 49Mpa 54Mpa 52MpaAdhesion failure Cohesive failure Adhesion failure Cohesive failure Cohesive failure

Impact energy load4730 kgmax height 2310158401015840

2318 J 2688 J 1854 J 2688 J 2688 J

Scratch resistance 10Kg passed 10Kg passed 10Kg passed 10Kg passed 10Kg passedFlexibility 140∘ passed 140∘ passed 140∘ passed 140∘ passed 140∘ passedTensile strength 846Mpa 576MPA 507MPa 1037MPa 1058MPaTaber abrasion results byweight loss (gm) 01277 00945 02080 00981 01073

Contact angle 5534 5234 6224 7474 6720

Table 6 Comparative corrosion test results of different kinds of surface tolerant coatings

SystemsSalt spray test (SST) Log (119885Ohm) Corrosion rate

(mpy-miles peryear)0ndash500 hours 500ndash1000 hours 1000ndash2000 hours 0 hour 500 hours 1000 hours 2000

hours

Benchmark 1Initiation of

blistering at 300hours

Number ofblisters incresed

Large blisters atthe centre and

edges65 48 38 2 3036mpy

Benchmark 2Initiation of

blistering at 350hours

Number ofblisters incresed

Number ofblisters increased 55 42 33 29 0795mpy

Benchmark 3 No blisteringLarge blisters atthe centre and

edges

Large number ofsmall edges 38 32 3 29 0420mpy

STC1 No blistering No blisteringInitiation of

blistering at 1600hours

75 48 42 41 0133mpy

STC2 No blistering No blisteringInitiation of

blistering at 1500hours

65 55 48 41 0311mpy

blistering and delamination even under severe temperaturegradients From Figure 13 it can be seen that initially theSTC1 shows higher value of coating resistance and the slope isless steep than the STC2The results show that the coatings atthis time were good shielding layers with large impedancesand the matrix was protected well After 500 hrs the poreresistance started decreasing assuming that the electrolytesolution was penetrating through the pores of the coatings(Figure 13 and Table 6) This could be because there was nopath in the coatings that allowed the electrolyte to reach thesubstrate with increasing exposure time The coating layerwas gradually attacked and thinned down by the electrolytewhich led to a decrease in the coating resistance (119877119901) becauseelectrolyte was transported to the metal substrate throughionic conducting paths in the coating The other benchmarkproducts show relatively less coating resistance

4 Conclusions

(1) Zinc dust pigmented surface tolerant coating (STC1)and micaceous iron oxide pigmented surface tolerant

14 12 10 08 06 04 02 00

log

(cur

rent

A)

Potential (V versus Calomel)

Benchmark 1Benchmark 2Benchmark 3

STC1STC2

minus100

minus95

minus90

minus85

minus80

minus75

minus70

minus65

minus60

minus55

minus50

minus45

Figure 11 Comparative Tafel plots of STC1 and 2 and benchmarks1 2 and 3

14 Journal of Coatings

16 20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

9

500 hours1000 hours

2000 hours0 hour

log

(ZO

hm)

log (freqHz)

(a)

20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

log (freqHz)

500 hours1000 hours

0 hour2000 hours

log

(ZO

hm)

(b)

18 21 24 27 30 33 36 39 42 45 4824

26

28

30

32

34

36

38

0 hours500 hours

2000 hours1000 hours

log (freqHz)

log

(ZO

hm)

(c)

16 20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

500 hours2000 hours

0 hour1000 hours

log (freqHz)

log

(ZO

hm)

(d)

20 24 28 32 36 40 44 48 5220

25

30

35

40

45

50

55

60

65

1000 hours2000 hours

500 hours0 hour

log (freqHz)

log

(ZO

hm)

(e)

Figure 12 Bode plots of various coating systems (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

Journal of Coatings 15

0 500 1000 1500 20000

1

2

3

4

5

6

7

8

Time (h)

Benchmark 1Benchmark 2Benchmark 3

STC1STC2

log

(ZO

hm)

Figure 13 Pore resistance with time for various coating systems

coating (STC2) were found to form a uniform coatingfilm over moist oil contaminated and surface pre-pared hot rolled sheets Excellent surface compatibil-ity to wet surface and good interfacial adhesion maybe due to low surface tension (28Nm) of the coatingscompared to competitive coatings (gt30Nm)

(2) The results of impact resistance tensile strength abra-sion resistance scratch resistance flexibility and pulloff adhesion were found superior than other availableproducts

(3) Anticorrosive pigments such as zinc dust (responsiblefor superior cathodic protection because of its lowerreduction potential than iron) and MIO (flaky shapewhich provide torturous path to the penetration ofcorrosive electrolytes) in the system have shown sig-nificant resistance against migration of chloride ionsand water and the free space between the particle andthe resin was less and thus restricted the penetrationof electrolyte through the pores in the coating filmThis is evident for high pore resistance over time in35 wt NaCl solution The rate of corrosion is alsofound 23 times less in 35 wt NaCl as compared tocompetitive products

(4) Marine simulation corrosion test as per ASTM B 117has shown significant delay in blister formation Thisis due to presence of anticorrosive pigments

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank Stanvac-Superon group forproviding funding and IIT Bombay and Tata Steel Industry

for providing research facilities for this work The authorswould like to thank all the Research Associate team also

References

[1] G C Soltz ldquoThe effects of substrate contaminates on the lifeof epoxy coatings in sea waterrdquo NSRP Report 0329 NationalShipbuilding Research Program 1991

[2] S B R Appleman S Boocock R E F Weaver and G CSoltz ldquoEffect of surface contaminates on coating liferdquo USDepartment of Transportation Federal Highway Administra-tion Publication FHWA-RD-91-011 1991

[3] National Steel and Shipbuilding NSRP Report ldquoPower ToolCleaning an alternate for abrasive blastingrdquo 1993

[4] J W Peart Evaluation of Coatings Applied on Less than IdealSurfaces withPeterson builders inc sturgeon bay Wis USA1995

[5] ldquoCuring Agent for Epoxy Resinsrdquo Three Bond Technical News1990

[6] N Rajgopalan and A S Khanna ldquoEffect of nano-ZnO in low-ering yellowing of aliphatic amine cured DGEBA-based epoxycoatings onUV exposurerdquo International Journal of Scientific andResearch vol 3 no 4 2013

[7] H Lee and K Neville Epoxy Resins Their Synthesis and Char-acterization and Curing of Epoxy Resins Their Applications andTechnology McGraw Hill

[8] Z W Wicks F N Jones and S P Pappas ldquoOrganic coatingsscience and technologyrdquo Dyes and Pigments vol 45 pp 85ndash862000

[9] L S Salem ldquoEpoxies for steelrdquo Journal of Protective Coatings andLinings vol 13 pp 77ndash98 1996

[10] M Ebert et al Polymer vol 32 no 3 p 139 1991[11] S Swier G van Assche W Vuchelen and B VanMele ldquoRole of

complex formation in the polymerization kinetics of modifiedepoxy-amine systemsrdquoMacromolecules vol 38 no 6 pp 2281ndash2288 2005

[12] S Shreepathi P Bajaj and B P Mallik ldquoElectrochemical imp-edance spectroscopy investigations of epoxy zinc rich coatingsrole of Zn content on corrosion protection mechanismrdquo Elec-trochimica Acta vol 55 no 18 pp 5129ndash5134 2010

[13] P A Soslashrensen S Kiil K Dam-Johansen and C E WeinellldquoAnticorrosive coatings a reviewrdquo Journal of Coatings Technol-ogy Research vol 6 no 2 pp 135ndash176 2009

[14] A Ruvolo-Filho and M Magaton ldquoEvaluating barrier proper-ties of acrylic polyurethane and aliphatic polyurethane coatingsloaded with micaceous iron oxide or red iron oxiderdquo PolymerPlastics Technology and Engineering vol 48 no 7 pp 682ndash6952009

[15] C Giudice J C Benftez and M M Linares ldquoZinc-rich epoxyprimers based on lamellar zinc dustrdquo Surface Coatings Interna-tional vol 80 no 6 pp 279ndash284 1997

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Journal of Coatings 9

Benchmark 1

(a)

Benchmark 2

(b)

Benchmark 3

(c)

STC1

(d)

STC2

(e)

Figure 7 Pull off adhesion test images of samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

somewhere in between (angle of 45 to 90∘) All coatings werehydrophilic in nature as their contact angle is less than 90∘For coating to be hydrophobic the contact anglemust be equalto or greater than 90∘ (Table 5 and Figure 9)

Tensile test (ASTM D638) this test method is designedto produce tensile property data for the control and specifi-cation of plastic materials by using ultimate tensile strengthmachine From the tensile strength data shown in Table 5it can be concluded that primer STC1 and primer STC2show the tensile strength 1037MPa and 1058MPa which arehigher as compared to other competitive products This maybe due to better bonding strength between epoxy matrix andthe respective pigments (Zn MIO) When the coating underload the stress is transferred from hard pigment to softerepoxy matrixThese pigments provide the good combinationof strength and toughness to the coating which results ingood tensile strength

Flexibility test (ASTM D522) and scratch resistance(ASTMD7027-13) flexibility test methods cover the determi-nation of the resistance to cracking (flexibility) of attached

organic coatings on substrates when elongated by usingconical mandrel bend testerThe specimen is clamped againsta conical mandrel and is bent around the mandrel by aroller mounted on a hand operated lever The diameter ofthe mandrel at the point where the coating starts to crackcan be determined from a scale marked on the specimenclamp Scratch resistance test method is able to characterizethe scratch resistance of polymers by measuring many signif-icant material parameters Table 5 shows that all the coatingsystems passed the maximum bending angle and scratchresistance test (Table 5)

34 Corrosion Studies

341 Salt Spray Test (ASTM B117) Samples were placed incorrosion-resistant self-supporting polyethylene casing Saltspray test provides a controlled corrosive environment whichhas been utilized to produce relative corrosion resistanceinformation for specimens of metals and coated metalsexposed in a given test chamber The coated panels were

10 Journal of Coatings

Benchmark 1

(a)

Benchmark 2

(b)

Benchmark 3

(c)

STC1

(d)

STC2

(e)

Figure 8 Impact resistance test of coated samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

exposed for 2000 hours in salt spray chamber The saltspray chamber was maintained at 35∘C containing 35NaClsolution Figure 10 shows the coated panels at zero 500 1000and 2000 hours After 500 hours initiation of blistering anddelamination took place in benchmark coatings and numberof blisters increased Increased susceptibility of blistering anddelamination may be due to the increased ionic permeabilityof the coating and the formation of amine carbamate (formedby absorbing carbon dioxide and moisture present in atmo-sphere by polyamine curative) over coating surface which is aclear indication of blushing As a comparison to others STC1provided efficient protective function against delaminationaround scribed areas ensured intense galvanic function of theprimer The other products show significant corrosion nearthe scribed areas large blisters and delamination Table 6summarizes the changes that took place in panels during saltspray exposure

342 Electrochemical Test Electrochemical tests were doneby using an electrochemical analyzer CH 604C from CH

instruments USA A three-electrode glass cell equipped witha platinum counter electrode an AgAgClCl- referenceelectrode with uncoated and coated substrates was used forthe electrochemical measurements Electrochemical mea-surements were performed under extreme environmentalconditions consisting of an aqueous air exposed sodiumchloride 35 NaCl solution at room temperature Eachsamplemasked by paraffin and only left 10 cm2 (10lowast 10) areain the solution The working electrode included an electricalconnection wire which was initially attaching the surface ofsample with conducting glue Samples were allowed to stabi-lize at their open circuit potential (OCP) The corrosion rateof coatings was measured by immersion studies conducted in35 wt NaCl solution at room temperature after 2000 hrs ofsalt spray exposure

343 Electrochemical Polarization Test Potentiodynamicpolarization was performed at 001 Vsec scan rate From thepolarization curves (Figure 11) and the data from Table 6 it is

Journal of Coatings 11

(a) (b)

(c) (d)

(e)

Figure 9 Contact angle test of coated samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

clear that the STC1 has higher OCP and lower current density(29 times 10minus7 A cmminus2) and corrosion rate as compared to MIObased STC2 and other benchmark coatingsThis is due to thepresence of zinc oxide which provides cathodic protection tothe substrate initially

Later due to formation of the corrosion product that isZnO the zinc in the system gets consumed and the formedproduct which provides barrier protection to the substrate Inthe case of STC2 theMIOflakes are responsible for providingbarrier protection but since there is no zinc its corrosion rateis higher than STC1 So it is confirmed that the other productshave higher current densities and corrosion rate than theSTC1 and STC2 due to their lack of cathodic protection as

well as less barrier protection because of the absence of zincand MIO flakes in coating material

344 Durability Test All electrochemical impedance spec-troscopy (EIS) spectra were acquired at the open circuitpotential in a frequency range from 10Hz to 1000Hz withac excitation amplitude of 5mVs in a 35 NaCl solutionat room temperature The durability of the coating systemswas estimated by exposing the samples at zero 500 1000 and2000 hours The pore resistance of the coatings is calculatedby plotting bode plots at respective hours

Initially the STC1 shows excellent barrier protectionowing to the homogenous distribution of zinc particles It has

12 Journal of Coatings

At 500 hours At 1000 hours At 2000 hoursAt 0 hour

(a)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(b)

At 500 hours At 1000 hours At 2000 hoursAt 0 hour

(c)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(d)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(e)

Figure 10 Salt spray images of coated panels at 0 500 1000 and 2000 hours (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1and (e) STC2

been observed that from zero to 500 hours there is decreasein pore resistance from log (Zohm) 65 to 48 this may bedue to initiation of corrosion process due to percolation ofthe electrolyte solution After that from 500 to 2000 hrs thereis not much change in pore resistance due to the consumedzinc that formed the corrosion product as ZnO as shown in

bode plots (Figure 12) This is attributed to filling up of voidspaces of the coatings by corrosion products of Zn whichprovide additional barrier protection In STC2 theMIOplaysa key role for providing barrier protection to the substrateIt provides the permeability allowing the transport of watervapor into and out of the film which is helpful in preventing

Journal of Coatings 13

Table 5 Comparative mechanical test results of different kinds of surface tolerant coatings

Benchmark 1 Benchmark 2 Benchmark 3 STC1 STC2

Pull off adhesion (Mpa) 5Mpa 54Mpa 49Mpa 54Mpa 52MpaAdhesion failure Cohesive failure Adhesion failure Cohesive failure Cohesive failure

Impact energy load4730 kgmax height 2310158401015840

2318 J 2688 J 1854 J 2688 J 2688 J

Scratch resistance 10Kg passed 10Kg passed 10Kg passed 10Kg passed 10Kg passedFlexibility 140∘ passed 140∘ passed 140∘ passed 140∘ passed 140∘ passedTensile strength 846Mpa 576MPA 507MPa 1037MPa 1058MPaTaber abrasion results byweight loss (gm) 01277 00945 02080 00981 01073

Contact angle 5534 5234 6224 7474 6720

Table 6 Comparative corrosion test results of different kinds of surface tolerant coatings

SystemsSalt spray test (SST) Log (119885Ohm) Corrosion rate

(mpy-miles peryear)0ndash500 hours 500ndash1000 hours 1000ndash2000 hours 0 hour 500 hours 1000 hours 2000

hours

Benchmark 1Initiation of

blistering at 300hours

Number ofblisters incresed

Large blisters atthe centre and

edges65 48 38 2 3036mpy

Benchmark 2Initiation of

blistering at 350hours

Number ofblisters incresed

Number ofblisters increased 55 42 33 29 0795mpy

Benchmark 3 No blisteringLarge blisters atthe centre and

edges

Large number ofsmall edges 38 32 3 29 0420mpy

STC1 No blistering No blisteringInitiation of

blistering at 1600hours

75 48 42 41 0133mpy

STC2 No blistering No blisteringInitiation of

blistering at 1500hours

65 55 48 41 0311mpy

blistering and delamination even under severe temperaturegradients From Figure 13 it can be seen that initially theSTC1 shows higher value of coating resistance and the slope isless steep than the STC2The results show that the coatings atthis time were good shielding layers with large impedancesand the matrix was protected well After 500 hrs the poreresistance started decreasing assuming that the electrolytesolution was penetrating through the pores of the coatings(Figure 13 and Table 6) This could be because there was nopath in the coatings that allowed the electrolyte to reach thesubstrate with increasing exposure time The coating layerwas gradually attacked and thinned down by the electrolytewhich led to a decrease in the coating resistance (119877119901) becauseelectrolyte was transported to the metal substrate throughionic conducting paths in the coating The other benchmarkproducts show relatively less coating resistance

4 Conclusions

(1) Zinc dust pigmented surface tolerant coating (STC1)and micaceous iron oxide pigmented surface tolerant

14 12 10 08 06 04 02 00

log

(cur

rent

A)

Potential (V versus Calomel)

Benchmark 1Benchmark 2Benchmark 3

STC1STC2

minus100

minus95

minus90

minus85

minus80

minus75

minus70

minus65

minus60

minus55

minus50

minus45

Figure 11 Comparative Tafel plots of STC1 and 2 and benchmarks1 2 and 3

14 Journal of Coatings

16 20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

9

500 hours1000 hours

2000 hours0 hour

log

(ZO

hm)

log (freqHz)

(a)

20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

log (freqHz)

500 hours1000 hours

0 hour2000 hours

log

(ZO

hm)

(b)

18 21 24 27 30 33 36 39 42 45 4824

26

28

30

32

34

36

38

0 hours500 hours

2000 hours1000 hours

log (freqHz)

log

(ZO

hm)

(c)

16 20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

500 hours2000 hours

0 hour1000 hours

log (freqHz)

log

(ZO

hm)

(d)

20 24 28 32 36 40 44 48 5220

25

30

35

40

45

50

55

60

65

1000 hours2000 hours

500 hours0 hour

log (freqHz)

log

(ZO

hm)

(e)

Figure 12 Bode plots of various coating systems (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

Journal of Coatings 15

0 500 1000 1500 20000

1

2

3

4

5

6

7

8

Time (h)

Benchmark 1Benchmark 2Benchmark 3

STC1STC2

log

(ZO

hm)

Figure 13 Pore resistance with time for various coating systems

coating (STC2) were found to form a uniform coatingfilm over moist oil contaminated and surface pre-pared hot rolled sheets Excellent surface compatibil-ity to wet surface and good interfacial adhesion maybe due to low surface tension (28Nm) of the coatingscompared to competitive coatings (gt30Nm)

(2) The results of impact resistance tensile strength abra-sion resistance scratch resistance flexibility and pulloff adhesion were found superior than other availableproducts

(3) Anticorrosive pigments such as zinc dust (responsiblefor superior cathodic protection because of its lowerreduction potential than iron) and MIO (flaky shapewhich provide torturous path to the penetration ofcorrosive electrolytes) in the system have shown sig-nificant resistance against migration of chloride ionsand water and the free space between the particle andthe resin was less and thus restricted the penetrationof electrolyte through the pores in the coating filmThis is evident for high pore resistance over time in35 wt NaCl solution The rate of corrosion is alsofound 23 times less in 35 wt NaCl as compared tocompetitive products

(4) Marine simulation corrosion test as per ASTM B 117has shown significant delay in blister formation Thisis due to presence of anticorrosive pigments

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank Stanvac-Superon group forproviding funding and IIT Bombay and Tata Steel Industry

for providing research facilities for this work The authorswould like to thank all the Research Associate team also

References

[1] G C Soltz ldquoThe effects of substrate contaminates on the lifeof epoxy coatings in sea waterrdquo NSRP Report 0329 NationalShipbuilding Research Program 1991

[2] S B R Appleman S Boocock R E F Weaver and G CSoltz ldquoEffect of surface contaminates on coating liferdquo USDepartment of Transportation Federal Highway Administra-tion Publication FHWA-RD-91-011 1991

[3] National Steel and Shipbuilding NSRP Report ldquoPower ToolCleaning an alternate for abrasive blastingrdquo 1993

[4] J W Peart Evaluation of Coatings Applied on Less than IdealSurfaces withPeterson builders inc sturgeon bay Wis USA1995

[5] ldquoCuring Agent for Epoxy Resinsrdquo Three Bond Technical News1990

[6] N Rajgopalan and A S Khanna ldquoEffect of nano-ZnO in low-ering yellowing of aliphatic amine cured DGEBA-based epoxycoatings onUV exposurerdquo International Journal of Scientific andResearch vol 3 no 4 2013

[7] H Lee and K Neville Epoxy Resins Their Synthesis and Char-acterization and Curing of Epoxy Resins Their Applications andTechnology McGraw Hill

[8] Z W Wicks F N Jones and S P Pappas ldquoOrganic coatingsscience and technologyrdquo Dyes and Pigments vol 45 pp 85ndash862000

[9] L S Salem ldquoEpoxies for steelrdquo Journal of Protective Coatings andLinings vol 13 pp 77ndash98 1996

[10] M Ebert et al Polymer vol 32 no 3 p 139 1991[11] S Swier G van Assche W Vuchelen and B VanMele ldquoRole of

complex formation in the polymerization kinetics of modifiedepoxy-amine systemsrdquoMacromolecules vol 38 no 6 pp 2281ndash2288 2005

[12] S Shreepathi P Bajaj and B P Mallik ldquoElectrochemical imp-edance spectroscopy investigations of epoxy zinc rich coatingsrole of Zn content on corrosion protection mechanismrdquo Elec-trochimica Acta vol 55 no 18 pp 5129ndash5134 2010

[13] P A Soslashrensen S Kiil K Dam-Johansen and C E WeinellldquoAnticorrosive coatings a reviewrdquo Journal of Coatings Technol-ogy Research vol 6 no 2 pp 135ndash176 2009

[14] A Ruvolo-Filho and M Magaton ldquoEvaluating barrier proper-ties of acrylic polyurethane and aliphatic polyurethane coatingsloaded with micaceous iron oxide or red iron oxiderdquo PolymerPlastics Technology and Engineering vol 48 no 7 pp 682ndash6952009

[15] C Giudice J C Benftez and M M Linares ldquoZinc-rich epoxyprimers based on lamellar zinc dustrdquo Surface Coatings Interna-tional vol 80 no 6 pp 279ndash284 1997

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

10 Journal of Coatings

Benchmark 1

(a)

Benchmark 2

(b)

Benchmark 3

(c)

STC1

(d)

STC2

(e)

Figure 8 Impact resistance test of coated samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

exposed for 2000 hours in salt spray chamber The saltspray chamber was maintained at 35∘C containing 35NaClsolution Figure 10 shows the coated panels at zero 500 1000and 2000 hours After 500 hours initiation of blistering anddelamination took place in benchmark coatings and numberof blisters increased Increased susceptibility of blistering anddelamination may be due to the increased ionic permeabilityof the coating and the formation of amine carbamate (formedby absorbing carbon dioxide and moisture present in atmo-sphere by polyamine curative) over coating surface which is aclear indication of blushing As a comparison to others STC1provided efficient protective function against delaminationaround scribed areas ensured intense galvanic function of theprimer The other products show significant corrosion nearthe scribed areas large blisters and delamination Table 6summarizes the changes that took place in panels during saltspray exposure

342 Electrochemical Test Electrochemical tests were doneby using an electrochemical analyzer CH 604C from CH

instruments USA A three-electrode glass cell equipped witha platinum counter electrode an AgAgClCl- referenceelectrode with uncoated and coated substrates was used forthe electrochemical measurements Electrochemical mea-surements were performed under extreme environmentalconditions consisting of an aqueous air exposed sodiumchloride 35 NaCl solution at room temperature Eachsamplemasked by paraffin and only left 10 cm2 (10lowast 10) areain the solution The working electrode included an electricalconnection wire which was initially attaching the surface ofsample with conducting glue Samples were allowed to stabi-lize at their open circuit potential (OCP) The corrosion rateof coatings was measured by immersion studies conducted in35 wt NaCl solution at room temperature after 2000 hrs ofsalt spray exposure

343 Electrochemical Polarization Test Potentiodynamicpolarization was performed at 001 Vsec scan rate From thepolarization curves (Figure 11) and the data from Table 6 it is

Journal of Coatings 11

(a) (b)

(c) (d)

(e)

Figure 9 Contact angle test of coated samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

clear that the STC1 has higher OCP and lower current density(29 times 10minus7 A cmminus2) and corrosion rate as compared to MIObased STC2 and other benchmark coatingsThis is due to thepresence of zinc oxide which provides cathodic protection tothe substrate initially

Later due to formation of the corrosion product that isZnO the zinc in the system gets consumed and the formedproduct which provides barrier protection to the substrate Inthe case of STC2 theMIOflakes are responsible for providingbarrier protection but since there is no zinc its corrosion rateis higher than STC1 So it is confirmed that the other productshave higher current densities and corrosion rate than theSTC1 and STC2 due to their lack of cathodic protection as

well as less barrier protection because of the absence of zincand MIO flakes in coating material

344 Durability Test All electrochemical impedance spec-troscopy (EIS) spectra were acquired at the open circuitpotential in a frequency range from 10Hz to 1000Hz withac excitation amplitude of 5mVs in a 35 NaCl solutionat room temperature The durability of the coating systemswas estimated by exposing the samples at zero 500 1000 and2000 hours The pore resistance of the coatings is calculatedby plotting bode plots at respective hours

Initially the STC1 shows excellent barrier protectionowing to the homogenous distribution of zinc particles It has

12 Journal of Coatings

At 500 hours At 1000 hours At 2000 hoursAt 0 hour

(a)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(b)

At 500 hours At 1000 hours At 2000 hoursAt 0 hour

(c)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(d)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(e)

Figure 10 Salt spray images of coated panels at 0 500 1000 and 2000 hours (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1and (e) STC2

been observed that from zero to 500 hours there is decreasein pore resistance from log (Zohm) 65 to 48 this may bedue to initiation of corrosion process due to percolation ofthe electrolyte solution After that from 500 to 2000 hrs thereis not much change in pore resistance due to the consumedzinc that formed the corrosion product as ZnO as shown in

bode plots (Figure 12) This is attributed to filling up of voidspaces of the coatings by corrosion products of Zn whichprovide additional barrier protection In STC2 theMIOplaysa key role for providing barrier protection to the substrateIt provides the permeability allowing the transport of watervapor into and out of the film which is helpful in preventing

Journal of Coatings 13

Table 5 Comparative mechanical test results of different kinds of surface tolerant coatings

Benchmark 1 Benchmark 2 Benchmark 3 STC1 STC2

Pull off adhesion (Mpa) 5Mpa 54Mpa 49Mpa 54Mpa 52MpaAdhesion failure Cohesive failure Adhesion failure Cohesive failure Cohesive failure

Impact energy load4730 kgmax height 2310158401015840

2318 J 2688 J 1854 J 2688 J 2688 J

Scratch resistance 10Kg passed 10Kg passed 10Kg passed 10Kg passed 10Kg passedFlexibility 140∘ passed 140∘ passed 140∘ passed 140∘ passed 140∘ passedTensile strength 846Mpa 576MPA 507MPa 1037MPa 1058MPaTaber abrasion results byweight loss (gm) 01277 00945 02080 00981 01073

Contact angle 5534 5234 6224 7474 6720

Table 6 Comparative corrosion test results of different kinds of surface tolerant coatings

SystemsSalt spray test (SST) Log (119885Ohm) Corrosion rate

(mpy-miles peryear)0ndash500 hours 500ndash1000 hours 1000ndash2000 hours 0 hour 500 hours 1000 hours 2000

hours

Benchmark 1Initiation of

blistering at 300hours

Number ofblisters incresed

Large blisters atthe centre and

edges65 48 38 2 3036mpy

Benchmark 2Initiation of

blistering at 350hours

Number ofblisters incresed

Number ofblisters increased 55 42 33 29 0795mpy

Benchmark 3 No blisteringLarge blisters atthe centre and

edges

Large number ofsmall edges 38 32 3 29 0420mpy

STC1 No blistering No blisteringInitiation of

blistering at 1600hours

75 48 42 41 0133mpy

STC2 No blistering No blisteringInitiation of

blistering at 1500hours

65 55 48 41 0311mpy

blistering and delamination even under severe temperaturegradients From Figure 13 it can be seen that initially theSTC1 shows higher value of coating resistance and the slope isless steep than the STC2The results show that the coatings atthis time were good shielding layers with large impedancesand the matrix was protected well After 500 hrs the poreresistance started decreasing assuming that the electrolytesolution was penetrating through the pores of the coatings(Figure 13 and Table 6) This could be because there was nopath in the coatings that allowed the electrolyte to reach thesubstrate with increasing exposure time The coating layerwas gradually attacked and thinned down by the electrolytewhich led to a decrease in the coating resistance (119877119901) becauseelectrolyte was transported to the metal substrate throughionic conducting paths in the coating The other benchmarkproducts show relatively less coating resistance

4 Conclusions

(1) Zinc dust pigmented surface tolerant coating (STC1)and micaceous iron oxide pigmented surface tolerant

14 12 10 08 06 04 02 00

log

(cur

rent

A)

Potential (V versus Calomel)

Benchmark 1Benchmark 2Benchmark 3

STC1STC2

minus100

minus95

minus90

minus85

minus80

minus75

minus70

minus65

minus60

minus55

minus50

minus45

Figure 11 Comparative Tafel plots of STC1 and 2 and benchmarks1 2 and 3

14 Journal of Coatings

16 20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

9

500 hours1000 hours

2000 hours0 hour

log

(ZO

hm)

log (freqHz)

(a)

20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

log (freqHz)

500 hours1000 hours

0 hour2000 hours

log

(ZO

hm)

(b)

18 21 24 27 30 33 36 39 42 45 4824

26

28

30

32

34

36

38

0 hours500 hours

2000 hours1000 hours

log (freqHz)

log

(ZO

hm)

(c)

16 20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

500 hours2000 hours

0 hour1000 hours

log (freqHz)

log

(ZO

hm)

(d)

20 24 28 32 36 40 44 48 5220

25

30

35

40

45

50

55

60

65

1000 hours2000 hours

500 hours0 hour

log (freqHz)

log

(ZO

hm)

(e)

Figure 12 Bode plots of various coating systems (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

Journal of Coatings 15

0 500 1000 1500 20000

1

2

3

4

5

6

7

8

Time (h)

Benchmark 1Benchmark 2Benchmark 3

STC1STC2

log

(ZO

hm)

Figure 13 Pore resistance with time for various coating systems

coating (STC2) were found to form a uniform coatingfilm over moist oil contaminated and surface pre-pared hot rolled sheets Excellent surface compatibil-ity to wet surface and good interfacial adhesion maybe due to low surface tension (28Nm) of the coatingscompared to competitive coatings (gt30Nm)

(2) The results of impact resistance tensile strength abra-sion resistance scratch resistance flexibility and pulloff adhesion were found superior than other availableproducts

(3) Anticorrosive pigments such as zinc dust (responsiblefor superior cathodic protection because of its lowerreduction potential than iron) and MIO (flaky shapewhich provide torturous path to the penetration ofcorrosive electrolytes) in the system have shown sig-nificant resistance against migration of chloride ionsand water and the free space between the particle andthe resin was less and thus restricted the penetrationof electrolyte through the pores in the coating filmThis is evident for high pore resistance over time in35 wt NaCl solution The rate of corrosion is alsofound 23 times less in 35 wt NaCl as compared tocompetitive products

(4) Marine simulation corrosion test as per ASTM B 117has shown significant delay in blister formation Thisis due to presence of anticorrosive pigments

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank Stanvac-Superon group forproviding funding and IIT Bombay and Tata Steel Industry

for providing research facilities for this work The authorswould like to thank all the Research Associate team also

References

[1] G C Soltz ldquoThe effects of substrate contaminates on the lifeof epoxy coatings in sea waterrdquo NSRP Report 0329 NationalShipbuilding Research Program 1991

[2] S B R Appleman S Boocock R E F Weaver and G CSoltz ldquoEffect of surface contaminates on coating liferdquo USDepartment of Transportation Federal Highway Administra-tion Publication FHWA-RD-91-011 1991

[3] National Steel and Shipbuilding NSRP Report ldquoPower ToolCleaning an alternate for abrasive blastingrdquo 1993

[4] J W Peart Evaluation of Coatings Applied on Less than IdealSurfaces withPeterson builders inc sturgeon bay Wis USA1995

[5] ldquoCuring Agent for Epoxy Resinsrdquo Three Bond Technical News1990

[6] N Rajgopalan and A S Khanna ldquoEffect of nano-ZnO in low-ering yellowing of aliphatic amine cured DGEBA-based epoxycoatings onUV exposurerdquo International Journal of Scientific andResearch vol 3 no 4 2013

[7] H Lee and K Neville Epoxy Resins Their Synthesis and Char-acterization and Curing of Epoxy Resins Their Applications andTechnology McGraw Hill

[8] Z W Wicks F N Jones and S P Pappas ldquoOrganic coatingsscience and technologyrdquo Dyes and Pigments vol 45 pp 85ndash862000

[9] L S Salem ldquoEpoxies for steelrdquo Journal of Protective Coatings andLinings vol 13 pp 77ndash98 1996

[10] M Ebert et al Polymer vol 32 no 3 p 139 1991[11] S Swier G van Assche W Vuchelen and B VanMele ldquoRole of

complex formation in the polymerization kinetics of modifiedepoxy-amine systemsrdquoMacromolecules vol 38 no 6 pp 2281ndash2288 2005

[12] S Shreepathi P Bajaj and B P Mallik ldquoElectrochemical imp-edance spectroscopy investigations of epoxy zinc rich coatingsrole of Zn content on corrosion protection mechanismrdquo Elec-trochimica Acta vol 55 no 18 pp 5129ndash5134 2010

[13] P A Soslashrensen S Kiil K Dam-Johansen and C E WeinellldquoAnticorrosive coatings a reviewrdquo Journal of Coatings Technol-ogy Research vol 6 no 2 pp 135ndash176 2009

[14] A Ruvolo-Filho and M Magaton ldquoEvaluating barrier proper-ties of acrylic polyurethane and aliphatic polyurethane coatingsloaded with micaceous iron oxide or red iron oxiderdquo PolymerPlastics Technology and Engineering vol 48 no 7 pp 682ndash6952009

[15] C Giudice J C Benftez and M M Linares ldquoZinc-rich epoxyprimers based on lamellar zinc dustrdquo Surface Coatings Interna-tional vol 80 no 6 pp 279ndash284 1997

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Journal of Coatings 11

(a) (b)

(c) (d)

(e)

Figure 9 Contact angle test of coated samples (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

clear that the STC1 has higher OCP and lower current density(29 times 10minus7 A cmminus2) and corrosion rate as compared to MIObased STC2 and other benchmark coatingsThis is due to thepresence of zinc oxide which provides cathodic protection tothe substrate initially

Later due to formation of the corrosion product that isZnO the zinc in the system gets consumed and the formedproduct which provides barrier protection to the substrate Inthe case of STC2 theMIOflakes are responsible for providingbarrier protection but since there is no zinc its corrosion rateis higher than STC1 So it is confirmed that the other productshave higher current densities and corrosion rate than theSTC1 and STC2 due to their lack of cathodic protection as

well as less barrier protection because of the absence of zincand MIO flakes in coating material

344 Durability Test All electrochemical impedance spec-troscopy (EIS) spectra were acquired at the open circuitpotential in a frequency range from 10Hz to 1000Hz withac excitation amplitude of 5mVs in a 35 NaCl solutionat room temperature The durability of the coating systemswas estimated by exposing the samples at zero 500 1000 and2000 hours The pore resistance of the coatings is calculatedby plotting bode plots at respective hours

Initially the STC1 shows excellent barrier protectionowing to the homogenous distribution of zinc particles It has

12 Journal of Coatings

At 500 hours At 1000 hours At 2000 hoursAt 0 hour

(a)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(b)

At 500 hours At 1000 hours At 2000 hoursAt 0 hour

(c)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(d)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(e)

Figure 10 Salt spray images of coated panels at 0 500 1000 and 2000 hours (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1and (e) STC2

been observed that from zero to 500 hours there is decreasein pore resistance from log (Zohm) 65 to 48 this may bedue to initiation of corrosion process due to percolation ofthe electrolyte solution After that from 500 to 2000 hrs thereis not much change in pore resistance due to the consumedzinc that formed the corrosion product as ZnO as shown in

bode plots (Figure 12) This is attributed to filling up of voidspaces of the coatings by corrosion products of Zn whichprovide additional barrier protection In STC2 theMIOplaysa key role for providing barrier protection to the substrateIt provides the permeability allowing the transport of watervapor into and out of the film which is helpful in preventing

Journal of Coatings 13

Table 5 Comparative mechanical test results of different kinds of surface tolerant coatings

Benchmark 1 Benchmark 2 Benchmark 3 STC1 STC2

Pull off adhesion (Mpa) 5Mpa 54Mpa 49Mpa 54Mpa 52MpaAdhesion failure Cohesive failure Adhesion failure Cohesive failure Cohesive failure

Impact energy load4730 kgmax height 2310158401015840

2318 J 2688 J 1854 J 2688 J 2688 J

Scratch resistance 10Kg passed 10Kg passed 10Kg passed 10Kg passed 10Kg passedFlexibility 140∘ passed 140∘ passed 140∘ passed 140∘ passed 140∘ passedTensile strength 846Mpa 576MPA 507MPa 1037MPa 1058MPaTaber abrasion results byweight loss (gm) 01277 00945 02080 00981 01073

Contact angle 5534 5234 6224 7474 6720

Table 6 Comparative corrosion test results of different kinds of surface tolerant coatings

SystemsSalt spray test (SST) Log (119885Ohm) Corrosion rate

(mpy-miles peryear)0ndash500 hours 500ndash1000 hours 1000ndash2000 hours 0 hour 500 hours 1000 hours 2000

hours

Benchmark 1Initiation of

blistering at 300hours

Number ofblisters incresed

Large blisters atthe centre and

edges65 48 38 2 3036mpy

Benchmark 2Initiation of

blistering at 350hours

Number ofblisters incresed

Number ofblisters increased 55 42 33 29 0795mpy

Benchmark 3 No blisteringLarge blisters atthe centre and

edges

Large number ofsmall edges 38 32 3 29 0420mpy

STC1 No blistering No blisteringInitiation of

blistering at 1600hours

75 48 42 41 0133mpy

STC2 No blistering No blisteringInitiation of

blistering at 1500hours

65 55 48 41 0311mpy

blistering and delamination even under severe temperaturegradients From Figure 13 it can be seen that initially theSTC1 shows higher value of coating resistance and the slope isless steep than the STC2The results show that the coatings atthis time were good shielding layers with large impedancesand the matrix was protected well After 500 hrs the poreresistance started decreasing assuming that the electrolytesolution was penetrating through the pores of the coatings(Figure 13 and Table 6) This could be because there was nopath in the coatings that allowed the electrolyte to reach thesubstrate with increasing exposure time The coating layerwas gradually attacked and thinned down by the electrolytewhich led to a decrease in the coating resistance (119877119901) becauseelectrolyte was transported to the metal substrate throughionic conducting paths in the coating The other benchmarkproducts show relatively less coating resistance

4 Conclusions

(1) Zinc dust pigmented surface tolerant coating (STC1)and micaceous iron oxide pigmented surface tolerant

14 12 10 08 06 04 02 00

log

(cur

rent

A)

Potential (V versus Calomel)

Benchmark 1Benchmark 2Benchmark 3

STC1STC2

minus100

minus95

minus90

minus85

minus80

minus75

minus70

minus65

minus60

minus55

minus50

minus45

Figure 11 Comparative Tafel plots of STC1 and 2 and benchmarks1 2 and 3

14 Journal of Coatings

16 20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

9

500 hours1000 hours

2000 hours0 hour

log

(ZO

hm)

log (freqHz)

(a)

20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

log (freqHz)

500 hours1000 hours

0 hour2000 hours

log

(ZO

hm)

(b)

18 21 24 27 30 33 36 39 42 45 4824

26

28

30

32

34

36

38

0 hours500 hours

2000 hours1000 hours

log (freqHz)

log

(ZO

hm)

(c)

16 20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

500 hours2000 hours

0 hour1000 hours

log (freqHz)

log

(ZO

hm)

(d)

20 24 28 32 36 40 44 48 5220

25

30

35

40

45

50

55

60

65

1000 hours2000 hours

500 hours0 hour

log (freqHz)

log

(ZO

hm)

(e)

Figure 12 Bode plots of various coating systems (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

Journal of Coatings 15

0 500 1000 1500 20000

1

2

3

4

5

6

7

8

Time (h)

Benchmark 1Benchmark 2Benchmark 3

STC1STC2

log

(ZO

hm)

Figure 13 Pore resistance with time for various coating systems

coating (STC2) were found to form a uniform coatingfilm over moist oil contaminated and surface pre-pared hot rolled sheets Excellent surface compatibil-ity to wet surface and good interfacial adhesion maybe due to low surface tension (28Nm) of the coatingscompared to competitive coatings (gt30Nm)

(2) The results of impact resistance tensile strength abra-sion resistance scratch resistance flexibility and pulloff adhesion were found superior than other availableproducts

(3) Anticorrosive pigments such as zinc dust (responsiblefor superior cathodic protection because of its lowerreduction potential than iron) and MIO (flaky shapewhich provide torturous path to the penetration ofcorrosive electrolytes) in the system have shown sig-nificant resistance against migration of chloride ionsand water and the free space between the particle andthe resin was less and thus restricted the penetrationof electrolyte through the pores in the coating filmThis is evident for high pore resistance over time in35 wt NaCl solution The rate of corrosion is alsofound 23 times less in 35 wt NaCl as compared tocompetitive products

(4) Marine simulation corrosion test as per ASTM B 117has shown significant delay in blister formation Thisis due to presence of anticorrosive pigments

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank Stanvac-Superon group forproviding funding and IIT Bombay and Tata Steel Industry

for providing research facilities for this work The authorswould like to thank all the Research Associate team also

References

[1] G C Soltz ldquoThe effects of substrate contaminates on the lifeof epoxy coatings in sea waterrdquo NSRP Report 0329 NationalShipbuilding Research Program 1991

[2] S B R Appleman S Boocock R E F Weaver and G CSoltz ldquoEffect of surface contaminates on coating liferdquo USDepartment of Transportation Federal Highway Administra-tion Publication FHWA-RD-91-011 1991

[3] National Steel and Shipbuilding NSRP Report ldquoPower ToolCleaning an alternate for abrasive blastingrdquo 1993

[4] J W Peart Evaluation of Coatings Applied on Less than IdealSurfaces withPeterson builders inc sturgeon bay Wis USA1995

[5] ldquoCuring Agent for Epoxy Resinsrdquo Three Bond Technical News1990

[6] N Rajgopalan and A S Khanna ldquoEffect of nano-ZnO in low-ering yellowing of aliphatic amine cured DGEBA-based epoxycoatings onUV exposurerdquo International Journal of Scientific andResearch vol 3 no 4 2013

[7] H Lee and K Neville Epoxy Resins Their Synthesis and Char-acterization and Curing of Epoxy Resins Their Applications andTechnology McGraw Hill

[8] Z W Wicks F N Jones and S P Pappas ldquoOrganic coatingsscience and technologyrdquo Dyes and Pigments vol 45 pp 85ndash862000

[9] L S Salem ldquoEpoxies for steelrdquo Journal of Protective Coatings andLinings vol 13 pp 77ndash98 1996

[10] M Ebert et al Polymer vol 32 no 3 p 139 1991[11] S Swier G van Assche W Vuchelen and B VanMele ldquoRole of

complex formation in the polymerization kinetics of modifiedepoxy-amine systemsrdquoMacromolecules vol 38 no 6 pp 2281ndash2288 2005

[12] S Shreepathi P Bajaj and B P Mallik ldquoElectrochemical imp-edance spectroscopy investigations of epoxy zinc rich coatingsrole of Zn content on corrosion protection mechanismrdquo Elec-trochimica Acta vol 55 no 18 pp 5129ndash5134 2010

[13] P A Soslashrensen S Kiil K Dam-Johansen and C E WeinellldquoAnticorrosive coatings a reviewrdquo Journal of Coatings Technol-ogy Research vol 6 no 2 pp 135ndash176 2009

[14] A Ruvolo-Filho and M Magaton ldquoEvaluating barrier proper-ties of acrylic polyurethane and aliphatic polyurethane coatingsloaded with micaceous iron oxide or red iron oxiderdquo PolymerPlastics Technology and Engineering vol 48 no 7 pp 682ndash6952009

[15] C Giudice J C Benftez and M M Linares ldquoZinc-rich epoxyprimers based on lamellar zinc dustrdquo Surface Coatings Interna-tional vol 80 no 6 pp 279ndash284 1997

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

12 Journal of Coatings

At 500 hours At 1000 hours At 2000 hoursAt 0 hour

(a)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(b)

At 500 hours At 1000 hours At 2000 hoursAt 0 hour

(c)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(d)

At 0 hour At 500 hours At 1000 hours At 2000 hours

(e)

Figure 10 Salt spray images of coated panels at 0 500 1000 and 2000 hours (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1and (e) STC2

been observed that from zero to 500 hours there is decreasein pore resistance from log (Zohm) 65 to 48 this may bedue to initiation of corrosion process due to percolation ofthe electrolyte solution After that from 500 to 2000 hrs thereis not much change in pore resistance due to the consumedzinc that formed the corrosion product as ZnO as shown in

bode plots (Figure 12) This is attributed to filling up of voidspaces of the coatings by corrosion products of Zn whichprovide additional barrier protection In STC2 theMIOplaysa key role for providing barrier protection to the substrateIt provides the permeability allowing the transport of watervapor into and out of the film which is helpful in preventing

Journal of Coatings 13

Table 5 Comparative mechanical test results of different kinds of surface tolerant coatings

Benchmark 1 Benchmark 2 Benchmark 3 STC1 STC2

Pull off adhesion (Mpa) 5Mpa 54Mpa 49Mpa 54Mpa 52MpaAdhesion failure Cohesive failure Adhesion failure Cohesive failure Cohesive failure

Impact energy load4730 kgmax height 2310158401015840

2318 J 2688 J 1854 J 2688 J 2688 J

Scratch resistance 10Kg passed 10Kg passed 10Kg passed 10Kg passed 10Kg passedFlexibility 140∘ passed 140∘ passed 140∘ passed 140∘ passed 140∘ passedTensile strength 846Mpa 576MPA 507MPa 1037MPa 1058MPaTaber abrasion results byweight loss (gm) 01277 00945 02080 00981 01073

Contact angle 5534 5234 6224 7474 6720

Table 6 Comparative corrosion test results of different kinds of surface tolerant coatings

SystemsSalt spray test (SST) Log (119885Ohm) Corrosion rate

(mpy-miles peryear)0ndash500 hours 500ndash1000 hours 1000ndash2000 hours 0 hour 500 hours 1000 hours 2000

hours

Benchmark 1Initiation of

blistering at 300hours

Number ofblisters incresed

Large blisters atthe centre and

edges65 48 38 2 3036mpy

Benchmark 2Initiation of

blistering at 350hours

Number ofblisters incresed

Number ofblisters increased 55 42 33 29 0795mpy

Benchmark 3 No blisteringLarge blisters atthe centre and

edges

Large number ofsmall edges 38 32 3 29 0420mpy

STC1 No blistering No blisteringInitiation of

blistering at 1600hours

75 48 42 41 0133mpy

STC2 No blistering No blisteringInitiation of

blistering at 1500hours

65 55 48 41 0311mpy

blistering and delamination even under severe temperaturegradients From Figure 13 it can be seen that initially theSTC1 shows higher value of coating resistance and the slope isless steep than the STC2The results show that the coatings atthis time were good shielding layers with large impedancesand the matrix was protected well After 500 hrs the poreresistance started decreasing assuming that the electrolytesolution was penetrating through the pores of the coatings(Figure 13 and Table 6) This could be because there was nopath in the coatings that allowed the electrolyte to reach thesubstrate with increasing exposure time The coating layerwas gradually attacked and thinned down by the electrolytewhich led to a decrease in the coating resistance (119877119901) becauseelectrolyte was transported to the metal substrate throughionic conducting paths in the coating The other benchmarkproducts show relatively less coating resistance

4 Conclusions

(1) Zinc dust pigmented surface tolerant coating (STC1)and micaceous iron oxide pigmented surface tolerant

14 12 10 08 06 04 02 00

log

(cur

rent

A)

Potential (V versus Calomel)

Benchmark 1Benchmark 2Benchmark 3

STC1STC2

minus100

minus95

minus90

minus85

minus80

minus75

minus70

minus65

minus60

minus55

minus50

minus45

Figure 11 Comparative Tafel plots of STC1 and 2 and benchmarks1 2 and 3

14 Journal of Coatings

16 20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

9

500 hours1000 hours

2000 hours0 hour

log

(ZO

hm)

log (freqHz)

(a)

20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

log (freqHz)

500 hours1000 hours

0 hour2000 hours

log

(ZO

hm)

(b)

18 21 24 27 30 33 36 39 42 45 4824

26

28

30

32

34

36

38

0 hours500 hours

2000 hours1000 hours

log (freqHz)

log

(ZO

hm)

(c)

16 20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

500 hours2000 hours

0 hour1000 hours

log (freqHz)

log

(ZO

hm)

(d)

20 24 28 32 36 40 44 48 5220

25

30

35

40

45

50

55

60

65

1000 hours2000 hours

500 hours0 hour

log (freqHz)

log

(ZO

hm)

(e)

Figure 12 Bode plots of various coating systems (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

Journal of Coatings 15

0 500 1000 1500 20000

1

2

3

4

5

6

7

8

Time (h)

Benchmark 1Benchmark 2Benchmark 3

STC1STC2

log

(ZO

hm)

Figure 13 Pore resistance with time for various coating systems

coating (STC2) were found to form a uniform coatingfilm over moist oil contaminated and surface pre-pared hot rolled sheets Excellent surface compatibil-ity to wet surface and good interfacial adhesion maybe due to low surface tension (28Nm) of the coatingscompared to competitive coatings (gt30Nm)

(2) The results of impact resistance tensile strength abra-sion resistance scratch resistance flexibility and pulloff adhesion were found superior than other availableproducts

(3) Anticorrosive pigments such as zinc dust (responsiblefor superior cathodic protection because of its lowerreduction potential than iron) and MIO (flaky shapewhich provide torturous path to the penetration ofcorrosive electrolytes) in the system have shown sig-nificant resistance against migration of chloride ionsand water and the free space between the particle andthe resin was less and thus restricted the penetrationof electrolyte through the pores in the coating filmThis is evident for high pore resistance over time in35 wt NaCl solution The rate of corrosion is alsofound 23 times less in 35 wt NaCl as compared tocompetitive products

(4) Marine simulation corrosion test as per ASTM B 117has shown significant delay in blister formation Thisis due to presence of anticorrosive pigments

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank Stanvac-Superon group forproviding funding and IIT Bombay and Tata Steel Industry

for providing research facilities for this work The authorswould like to thank all the Research Associate team also

References

[1] G C Soltz ldquoThe effects of substrate contaminates on the lifeof epoxy coatings in sea waterrdquo NSRP Report 0329 NationalShipbuilding Research Program 1991

[2] S B R Appleman S Boocock R E F Weaver and G CSoltz ldquoEffect of surface contaminates on coating liferdquo USDepartment of Transportation Federal Highway Administra-tion Publication FHWA-RD-91-011 1991

[3] National Steel and Shipbuilding NSRP Report ldquoPower ToolCleaning an alternate for abrasive blastingrdquo 1993

[4] J W Peart Evaluation of Coatings Applied on Less than IdealSurfaces withPeterson builders inc sturgeon bay Wis USA1995

[5] ldquoCuring Agent for Epoxy Resinsrdquo Three Bond Technical News1990

[6] N Rajgopalan and A S Khanna ldquoEffect of nano-ZnO in low-ering yellowing of aliphatic amine cured DGEBA-based epoxycoatings onUV exposurerdquo International Journal of Scientific andResearch vol 3 no 4 2013

[7] H Lee and K Neville Epoxy Resins Their Synthesis and Char-acterization and Curing of Epoxy Resins Their Applications andTechnology McGraw Hill

[8] Z W Wicks F N Jones and S P Pappas ldquoOrganic coatingsscience and technologyrdquo Dyes and Pigments vol 45 pp 85ndash862000

[9] L S Salem ldquoEpoxies for steelrdquo Journal of Protective Coatings andLinings vol 13 pp 77ndash98 1996

[10] M Ebert et al Polymer vol 32 no 3 p 139 1991[11] S Swier G van Assche W Vuchelen and B VanMele ldquoRole of

complex formation in the polymerization kinetics of modifiedepoxy-amine systemsrdquoMacromolecules vol 38 no 6 pp 2281ndash2288 2005

[12] S Shreepathi P Bajaj and B P Mallik ldquoElectrochemical imp-edance spectroscopy investigations of epoxy zinc rich coatingsrole of Zn content on corrosion protection mechanismrdquo Elec-trochimica Acta vol 55 no 18 pp 5129ndash5134 2010

[13] P A Soslashrensen S Kiil K Dam-Johansen and C E WeinellldquoAnticorrosive coatings a reviewrdquo Journal of Coatings Technol-ogy Research vol 6 no 2 pp 135ndash176 2009

[14] A Ruvolo-Filho and M Magaton ldquoEvaluating barrier proper-ties of acrylic polyurethane and aliphatic polyurethane coatingsloaded with micaceous iron oxide or red iron oxiderdquo PolymerPlastics Technology and Engineering vol 48 no 7 pp 682ndash6952009

[15] C Giudice J C Benftez and M M Linares ldquoZinc-rich epoxyprimers based on lamellar zinc dustrdquo Surface Coatings Interna-tional vol 80 no 6 pp 279ndash284 1997

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Journal of Coatings 13

Table 5 Comparative mechanical test results of different kinds of surface tolerant coatings

Benchmark 1 Benchmark 2 Benchmark 3 STC1 STC2

Pull off adhesion (Mpa) 5Mpa 54Mpa 49Mpa 54Mpa 52MpaAdhesion failure Cohesive failure Adhesion failure Cohesive failure Cohesive failure

Impact energy load4730 kgmax height 2310158401015840

2318 J 2688 J 1854 J 2688 J 2688 J

Scratch resistance 10Kg passed 10Kg passed 10Kg passed 10Kg passed 10Kg passedFlexibility 140∘ passed 140∘ passed 140∘ passed 140∘ passed 140∘ passedTensile strength 846Mpa 576MPA 507MPa 1037MPa 1058MPaTaber abrasion results byweight loss (gm) 01277 00945 02080 00981 01073

Contact angle 5534 5234 6224 7474 6720

Table 6 Comparative corrosion test results of different kinds of surface tolerant coatings

SystemsSalt spray test (SST) Log (119885Ohm) Corrosion rate

(mpy-miles peryear)0ndash500 hours 500ndash1000 hours 1000ndash2000 hours 0 hour 500 hours 1000 hours 2000

hours

Benchmark 1Initiation of

blistering at 300hours

Number ofblisters incresed

Large blisters atthe centre and

edges65 48 38 2 3036mpy

Benchmark 2Initiation of

blistering at 350hours

Number ofblisters incresed

Number ofblisters increased 55 42 33 29 0795mpy

Benchmark 3 No blisteringLarge blisters atthe centre and

edges

Large number ofsmall edges 38 32 3 29 0420mpy

STC1 No blistering No blisteringInitiation of

blistering at 1600hours

75 48 42 41 0133mpy

STC2 No blistering No blisteringInitiation of

blistering at 1500hours

65 55 48 41 0311mpy

blistering and delamination even under severe temperaturegradients From Figure 13 it can be seen that initially theSTC1 shows higher value of coating resistance and the slope isless steep than the STC2The results show that the coatings atthis time were good shielding layers with large impedancesand the matrix was protected well After 500 hrs the poreresistance started decreasing assuming that the electrolytesolution was penetrating through the pores of the coatings(Figure 13 and Table 6) This could be because there was nopath in the coatings that allowed the electrolyte to reach thesubstrate with increasing exposure time The coating layerwas gradually attacked and thinned down by the electrolytewhich led to a decrease in the coating resistance (119877119901) becauseelectrolyte was transported to the metal substrate throughionic conducting paths in the coating The other benchmarkproducts show relatively less coating resistance

4 Conclusions

(1) Zinc dust pigmented surface tolerant coating (STC1)and micaceous iron oxide pigmented surface tolerant

14 12 10 08 06 04 02 00

log

(cur

rent

A)

Potential (V versus Calomel)

Benchmark 1Benchmark 2Benchmark 3

STC1STC2

minus100

minus95

minus90

minus85

minus80

minus75

minus70

minus65

minus60

minus55

minus50

minus45

Figure 11 Comparative Tafel plots of STC1 and 2 and benchmarks1 2 and 3

14 Journal of Coatings

16 20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

9

500 hours1000 hours

2000 hours0 hour

log

(ZO

hm)

log (freqHz)

(a)

20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

log (freqHz)

500 hours1000 hours

0 hour2000 hours

log

(ZO

hm)

(b)

18 21 24 27 30 33 36 39 42 45 4824

26

28

30

32

34

36

38

0 hours500 hours

2000 hours1000 hours

log (freqHz)

log

(ZO

hm)

(c)

16 20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

500 hours2000 hours

0 hour1000 hours

log (freqHz)

log

(ZO

hm)

(d)

20 24 28 32 36 40 44 48 5220

25

30

35

40

45

50

55

60

65

1000 hours2000 hours

500 hours0 hour

log (freqHz)

log

(ZO

hm)

(e)

Figure 12 Bode plots of various coating systems (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

Journal of Coatings 15

0 500 1000 1500 20000

1

2

3

4

5

6

7

8

Time (h)

Benchmark 1Benchmark 2Benchmark 3

STC1STC2

log

(ZO

hm)

Figure 13 Pore resistance with time for various coating systems

coating (STC2) were found to form a uniform coatingfilm over moist oil contaminated and surface pre-pared hot rolled sheets Excellent surface compatibil-ity to wet surface and good interfacial adhesion maybe due to low surface tension (28Nm) of the coatingscompared to competitive coatings (gt30Nm)

(2) The results of impact resistance tensile strength abra-sion resistance scratch resistance flexibility and pulloff adhesion were found superior than other availableproducts

(3) Anticorrosive pigments such as zinc dust (responsiblefor superior cathodic protection because of its lowerreduction potential than iron) and MIO (flaky shapewhich provide torturous path to the penetration ofcorrosive electrolytes) in the system have shown sig-nificant resistance against migration of chloride ionsand water and the free space between the particle andthe resin was less and thus restricted the penetrationof electrolyte through the pores in the coating filmThis is evident for high pore resistance over time in35 wt NaCl solution The rate of corrosion is alsofound 23 times less in 35 wt NaCl as compared tocompetitive products

(4) Marine simulation corrosion test as per ASTM B 117has shown significant delay in blister formation Thisis due to presence of anticorrosive pigments

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank Stanvac-Superon group forproviding funding and IIT Bombay and Tata Steel Industry

for providing research facilities for this work The authorswould like to thank all the Research Associate team also

References

[1] G C Soltz ldquoThe effects of substrate contaminates on the lifeof epoxy coatings in sea waterrdquo NSRP Report 0329 NationalShipbuilding Research Program 1991

[2] S B R Appleman S Boocock R E F Weaver and G CSoltz ldquoEffect of surface contaminates on coating liferdquo USDepartment of Transportation Federal Highway Administra-tion Publication FHWA-RD-91-011 1991

[3] National Steel and Shipbuilding NSRP Report ldquoPower ToolCleaning an alternate for abrasive blastingrdquo 1993

[4] J W Peart Evaluation of Coatings Applied on Less than IdealSurfaces withPeterson builders inc sturgeon bay Wis USA1995

[5] ldquoCuring Agent for Epoxy Resinsrdquo Three Bond Technical News1990

[6] N Rajgopalan and A S Khanna ldquoEffect of nano-ZnO in low-ering yellowing of aliphatic amine cured DGEBA-based epoxycoatings onUV exposurerdquo International Journal of Scientific andResearch vol 3 no 4 2013

[7] H Lee and K Neville Epoxy Resins Their Synthesis and Char-acterization and Curing of Epoxy Resins Their Applications andTechnology McGraw Hill

[8] Z W Wicks F N Jones and S P Pappas ldquoOrganic coatingsscience and technologyrdquo Dyes and Pigments vol 45 pp 85ndash862000

[9] L S Salem ldquoEpoxies for steelrdquo Journal of Protective Coatings andLinings vol 13 pp 77ndash98 1996

[10] M Ebert et al Polymer vol 32 no 3 p 139 1991[11] S Swier G van Assche W Vuchelen and B VanMele ldquoRole of

complex formation in the polymerization kinetics of modifiedepoxy-amine systemsrdquoMacromolecules vol 38 no 6 pp 2281ndash2288 2005

[12] S Shreepathi P Bajaj and B P Mallik ldquoElectrochemical imp-edance spectroscopy investigations of epoxy zinc rich coatingsrole of Zn content on corrosion protection mechanismrdquo Elec-trochimica Acta vol 55 no 18 pp 5129ndash5134 2010

[13] P A Soslashrensen S Kiil K Dam-Johansen and C E WeinellldquoAnticorrosive coatings a reviewrdquo Journal of Coatings Technol-ogy Research vol 6 no 2 pp 135ndash176 2009

[14] A Ruvolo-Filho and M Magaton ldquoEvaluating barrier proper-ties of acrylic polyurethane and aliphatic polyurethane coatingsloaded with micaceous iron oxide or red iron oxiderdquo PolymerPlastics Technology and Engineering vol 48 no 7 pp 682ndash6952009

[15] C Giudice J C Benftez and M M Linares ldquoZinc-rich epoxyprimers based on lamellar zinc dustrdquo Surface Coatings Interna-tional vol 80 no 6 pp 279ndash284 1997

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

14 Journal of Coatings

16 20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

9

500 hours1000 hours

2000 hours0 hour

log

(ZO

hm)

log (freqHz)

(a)

20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

log (freqHz)

500 hours1000 hours

0 hour2000 hours

log

(ZO

hm)

(b)

18 21 24 27 30 33 36 39 42 45 4824

26

28

30

32

34

36

38

0 hours500 hours

2000 hours1000 hours

log (freqHz)

log

(ZO

hm)

(c)

16 20 24 28 32 36 40 44 48 522

3

4

5

6

7

8

500 hours2000 hours

0 hour1000 hours

log (freqHz)

log

(ZO

hm)

(d)

20 24 28 32 36 40 44 48 5220

25

30

35

40

45

50

55

60

65

1000 hours2000 hours

500 hours0 hour

log (freqHz)

log

(ZO

hm)

(e)

Figure 12 Bode plots of various coating systems (a) benchmark 1 (b) benchmark 2 (c) benchmark 3 (d) STC1 and (e) STC2

Journal of Coatings 15

0 500 1000 1500 20000

1

2

3

4

5

6

7

8

Time (h)

Benchmark 1Benchmark 2Benchmark 3

STC1STC2

log

(ZO

hm)

Figure 13 Pore resistance with time for various coating systems

coating (STC2) were found to form a uniform coatingfilm over moist oil contaminated and surface pre-pared hot rolled sheets Excellent surface compatibil-ity to wet surface and good interfacial adhesion maybe due to low surface tension (28Nm) of the coatingscompared to competitive coatings (gt30Nm)

(2) The results of impact resistance tensile strength abra-sion resistance scratch resistance flexibility and pulloff adhesion were found superior than other availableproducts

(3) Anticorrosive pigments such as zinc dust (responsiblefor superior cathodic protection because of its lowerreduction potential than iron) and MIO (flaky shapewhich provide torturous path to the penetration ofcorrosive electrolytes) in the system have shown sig-nificant resistance against migration of chloride ionsand water and the free space between the particle andthe resin was less and thus restricted the penetrationof electrolyte through the pores in the coating filmThis is evident for high pore resistance over time in35 wt NaCl solution The rate of corrosion is alsofound 23 times less in 35 wt NaCl as compared tocompetitive products

(4) Marine simulation corrosion test as per ASTM B 117has shown significant delay in blister formation Thisis due to presence of anticorrosive pigments

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank Stanvac-Superon group forproviding funding and IIT Bombay and Tata Steel Industry

for providing research facilities for this work The authorswould like to thank all the Research Associate team also

References

[1] G C Soltz ldquoThe effects of substrate contaminates on the lifeof epoxy coatings in sea waterrdquo NSRP Report 0329 NationalShipbuilding Research Program 1991

[2] S B R Appleman S Boocock R E F Weaver and G CSoltz ldquoEffect of surface contaminates on coating liferdquo USDepartment of Transportation Federal Highway Administra-tion Publication FHWA-RD-91-011 1991

[3] National Steel and Shipbuilding NSRP Report ldquoPower ToolCleaning an alternate for abrasive blastingrdquo 1993

[4] J W Peart Evaluation of Coatings Applied on Less than IdealSurfaces withPeterson builders inc sturgeon bay Wis USA1995

[5] ldquoCuring Agent for Epoxy Resinsrdquo Three Bond Technical News1990

[6] N Rajgopalan and A S Khanna ldquoEffect of nano-ZnO in low-ering yellowing of aliphatic amine cured DGEBA-based epoxycoatings onUV exposurerdquo International Journal of Scientific andResearch vol 3 no 4 2013

[7] H Lee and K Neville Epoxy Resins Their Synthesis and Char-acterization and Curing of Epoxy Resins Their Applications andTechnology McGraw Hill

[8] Z W Wicks F N Jones and S P Pappas ldquoOrganic coatingsscience and technologyrdquo Dyes and Pigments vol 45 pp 85ndash862000

[9] L S Salem ldquoEpoxies for steelrdquo Journal of Protective Coatings andLinings vol 13 pp 77ndash98 1996

[10] M Ebert et al Polymer vol 32 no 3 p 139 1991[11] S Swier G van Assche W Vuchelen and B VanMele ldquoRole of

complex formation in the polymerization kinetics of modifiedepoxy-amine systemsrdquoMacromolecules vol 38 no 6 pp 2281ndash2288 2005

[12] S Shreepathi P Bajaj and B P Mallik ldquoElectrochemical imp-edance spectroscopy investigations of epoxy zinc rich coatingsrole of Zn content on corrosion protection mechanismrdquo Elec-trochimica Acta vol 55 no 18 pp 5129ndash5134 2010

[13] P A Soslashrensen S Kiil K Dam-Johansen and C E WeinellldquoAnticorrosive coatings a reviewrdquo Journal of Coatings Technol-ogy Research vol 6 no 2 pp 135ndash176 2009

[14] A Ruvolo-Filho and M Magaton ldquoEvaluating barrier proper-ties of acrylic polyurethane and aliphatic polyurethane coatingsloaded with micaceous iron oxide or red iron oxiderdquo PolymerPlastics Technology and Engineering vol 48 no 7 pp 682ndash6952009

[15] C Giudice J C Benftez and M M Linares ldquoZinc-rich epoxyprimers based on lamellar zinc dustrdquo Surface Coatings Interna-tional vol 80 no 6 pp 279ndash284 1997

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Journal of Coatings 15

0 500 1000 1500 20000

1

2

3

4

5

6

7

8

Time (h)

Benchmark 1Benchmark 2Benchmark 3

STC1STC2

log

(ZO

hm)

Figure 13 Pore resistance with time for various coating systems

coating (STC2) were found to form a uniform coatingfilm over moist oil contaminated and surface pre-pared hot rolled sheets Excellent surface compatibil-ity to wet surface and good interfacial adhesion maybe due to low surface tension (28Nm) of the coatingscompared to competitive coatings (gt30Nm)

(2) The results of impact resistance tensile strength abra-sion resistance scratch resistance flexibility and pulloff adhesion were found superior than other availableproducts

(3) Anticorrosive pigments such as zinc dust (responsiblefor superior cathodic protection because of its lowerreduction potential than iron) and MIO (flaky shapewhich provide torturous path to the penetration ofcorrosive electrolytes) in the system have shown sig-nificant resistance against migration of chloride ionsand water and the free space between the particle andthe resin was less and thus restricted the penetrationof electrolyte through the pores in the coating filmThis is evident for high pore resistance over time in35 wt NaCl solution The rate of corrosion is alsofound 23 times less in 35 wt NaCl as compared tocompetitive products

(4) Marine simulation corrosion test as per ASTM B 117has shown significant delay in blister formation Thisis due to presence of anticorrosive pigments

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank Stanvac-Superon group forproviding funding and IIT Bombay and Tata Steel Industry

for providing research facilities for this work The authorswould like to thank all the Research Associate team also

References

[1] G C Soltz ldquoThe effects of substrate contaminates on the lifeof epoxy coatings in sea waterrdquo NSRP Report 0329 NationalShipbuilding Research Program 1991

[2] S B R Appleman S Boocock R E F Weaver and G CSoltz ldquoEffect of surface contaminates on coating liferdquo USDepartment of Transportation Federal Highway Administra-tion Publication FHWA-RD-91-011 1991

[3] National Steel and Shipbuilding NSRP Report ldquoPower ToolCleaning an alternate for abrasive blastingrdquo 1993

[4] J W Peart Evaluation of Coatings Applied on Less than IdealSurfaces withPeterson builders inc sturgeon bay Wis USA1995

[5] ldquoCuring Agent for Epoxy Resinsrdquo Three Bond Technical News1990

[6] N Rajgopalan and A S Khanna ldquoEffect of nano-ZnO in low-ering yellowing of aliphatic amine cured DGEBA-based epoxycoatings onUV exposurerdquo International Journal of Scientific andResearch vol 3 no 4 2013

[7] H Lee and K Neville Epoxy Resins Their Synthesis and Char-acterization and Curing of Epoxy Resins Their Applications andTechnology McGraw Hill

[8] Z W Wicks F N Jones and S P Pappas ldquoOrganic coatingsscience and technologyrdquo Dyes and Pigments vol 45 pp 85ndash862000

[9] L S Salem ldquoEpoxies for steelrdquo Journal of Protective Coatings andLinings vol 13 pp 77ndash98 1996

[10] M Ebert et al Polymer vol 32 no 3 p 139 1991[11] S Swier G van Assche W Vuchelen and B VanMele ldquoRole of

complex formation in the polymerization kinetics of modifiedepoxy-amine systemsrdquoMacromolecules vol 38 no 6 pp 2281ndash2288 2005

[12] S Shreepathi P Bajaj and B P Mallik ldquoElectrochemical imp-edance spectroscopy investigations of epoxy zinc rich coatingsrole of Zn content on corrosion protection mechanismrdquo Elec-trochimica Acta vol 55 no 18 pp 5129ndash5134 2010

[13] P A Soslashrensen S Kiil K Dam-Johansen and C E WeinellldquoAnticorrosive coatings a reviewrdquo Journal of Coatings Technol-ogy Research vol 6 no 2 pp 135ndash176 2009

[14] A Ruvolo-Filho and M Magaton ldquoEvaluating barrier proper-ties of acrylic polyurethane and aliphatic polyurethane coatingsloaded with micaceous iron oxide or red iron oxiderdquo PolymerPlastics Technology and Engineering vol 48 no 7 pp 682ndash6952009

[15] C Giudice J C Benftez and M M Linares ldquoZinc-rich epoxyprimers based on lamellar zinc dustrdquo Surface Coatings Interna-tional vol 80 no 6 pp 279ndash284 1997

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials