Research Article A Revisit to the Corrosion Inhibition of Aluminum in Aqueous …downloads.hindawi.com › journals › ijc › 2013 › 508596.pdf · 2019-07-31 · A Revisit to

Hindawi Publishing CorporationInternational Journal of CorrosionVolume 2013 Article ID 508596 8 pageshttpdxdoiorg1011552013508596

Research ArticleA Revisit to the Corrosion Inhibition of Aluminum inAqueous Alkaline Solutions by Water-Soluble Alginates andPectates as Anionic Polyelectrolyte Inhibitors

Refat Hassan1 Ishaq Zaafarany2 Adil Gobouri3 and Hideo Takagi4

1 Chemistry Department Faculty of Science Assiut University Assiut 71516 Egypt2 Chemistry Department Faculty of Applied Sciences Umm Al-Qura University Makkah Al-Mukarramah 13401 Saudi Arabia3 Chemistry Department Faculty of Science Taif University Taif 21995 Saudi Arabia4Chemistry Department Research Center for Materials Science Nagoya University Nagoya 464- 01 Japan

Correspondence should be addressed to Refat Hassan rmhassan2002yahoocom

Received 24 July 2013 Accepted 16 September 2013

Academic Editor Flavio Deflorian

Copyright copy 2013 Refat Hassan 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

The corrosion behavior of aluminum (Al) in alkalinemedia in presence of some natural polymer inhibitors has been reinvestigatedThe inhibition action of the tested inhibitors was found to obey both Langmuir and Freundlich isotherms models The inhibitionefficiency was found to increase with increasing the inhibitors concentration and decrease with increasing the temperaturesuggesting physical adsorption mechanism Factors such as the concentration and geometrical structure of the inhibitorconcentration of the corrosive medium and temperature affecting the corrosion rates were examinedThe kinetic parameters wereevaluated and a suitable corrosion mechanism consistent with the kinetic results obtained is suggested and discussed

1 Introduction

Aluminum and its alloys are known as attractive materialswhich have a wide application in engineering technologyowing to their low cost light weights and high thermal andelectrical conductivities [1]They also showed high resistivitytoward a wide variety of corrosion environments [2] Thisbehavior may be attributed to the formation of a protectivetightly adhered invisible oxide film on the metal surface

The remarkable potential applications of aluminum inindustrial technology particularly in aluminum-air industryencouraged many investigators to study the influence ofvarious inhibitors on Al dissolution in both acidic [1ndash14] andalkaline [15ndash20] media since the kinetics of dissolution isreduced by the presence of a thick oxide-hydroxide film at theanode surface Most of workers have directed their researchtowards concentrated alkalinemedia which permit optimumperformance of the air cathode and a low level of aluminumpolarization during normal operation [20]

Unfortunately most of the inhibitors available in themarkets are not only expensive but also toxic to living

beings Again the safety of environmental issues of corrosioninhibitors which may be arise in industry has always beena global concern Therefore the cheap nontoxic ecologi-cal and friendly corrosion inhibitors are of more impor-tance Consequently many alternative ecofriendly corrosioninhibitors have been developed [17]

Recently the influence of alginate and pectate anionicpolyelectrolyte as natural polymers inhibitors on the behav-ior of dissolution of Al metal in alkaline solutions hasbeen reported elsewhere [21] Unfortunately the adsorptionisotherm models have not been tested to the experimentalresults Hence the information on the corrosion mechanismstill remains incomplete

In view of the above arguments and our interest inphysicochemical properties of macromolecules in particu-larly biodegradable and nontoxic polysaccharides [22ndash38]the present work seems to merit a further reinvestigationwith the aims at shedding more highlights on the corro-sion behavior in terms of fitting the kinetic data to theadsorption isotherm models Furthermore this study aimsto throw some light on the role of the functional groups

2 International Journal of Corrosion

and geometrical configuration of the inhibitors used in theadsorption process as well as the influence of the nature ofthe medium on the corrosion mechanism

2 Experimental

21 Materials All materials used were of analytical gradeDoubly distilled conductivity water was used in all prepara-tions The temperature was controlled within plusmn01∘C

Sodium alginate (ALG) and sodium pectate (PEC)were purchased from Fluka and were used withoutfurther purification The degree of substitution was foundto be 43mmol gminus1 (091molmolminus1) and 41mmol gminus1(082molmolminus1) for alginates and pectates respectively

Aluminum metal used was of 9998 purity (VentronCrop Osaka Japan)

22 Preparation of Inhibitor Sols Sols of alginate and pectatepolysaccharides were prepared as described earlier [21 22]This process was performed by stepwise addition of the pow-der reagent to bidistilled water whilst rapidly and vigorouslystirring the solutions to avoid the formation of lumps whichswell with difficulty Then the prepared alginate or pectatesols were left at room temperature (25∘C) for about 24 h inorder to become air-bubbles-free being before used

23 Measurement Techniques Although the weight-losstechnique is the most employed method to acquire the cor-rosion rate data for metal coupons at natural environmentalcorrosion tests it makes the corrosion rate obtained a long-term average that is it needs a long-time immersion There-fore gasometric method is usually preferred for assessingthe inhibitive performance in case of short-time immersionof the corrosive metals in acidic or alkaline solutions as inthe cited work The technique was the same as describedelsewhere [18] The course of reaction was followed bymeasuring the evolved hydrogen gas as a function of time

Some kinetic measurements were performed using theclassical weight-loss method [1 13 39 40] in order to checkthe reproducibility of the gasometric data obtained Fortu-nately the results obtained for the corrosion rates in bothtechniqueswere found to be correlatedwith each otherwithinexperimental errors (plusmn5) This fact may indicate the repro-ducibility of the results obtained by the gasometric method

All experiments were repeated using different concentra-tions of NaOH and inhibitors at various temperatures Thecited results were at least an average of four experimentalruns The corrosion medium was not stirred during the testThe experimental data obtainedwere found towell agree withthat reported earlier (within experimental errors plusmn5) [21]

3 Results and Discussions

31 Hydrogen Evolution and Weight-Loss Measurements Thevolume of the evolved H

2gas (or the loss in Al weight) as

a function of time may be taken as the rate of dissolution

0 1 2 30

2

4

6

Time (min)

VH2

(mL

cm2)

Figure 1 A typical plot of the evolved119881H2 versus time for corrosionof Al in alkaline media in absence of inhibitors at 30∘C [OHminus] =40mol dmminus3

of aluminum in sodium hydroxide and can be expressedrespectively by

119877119888=

119881H2

119871 sdot 119905

(1)

119877119888=Δ119882

119871 sdot 119905

(2)

where119877119888is the corrosion rate 119871 is the surface area of Almetal

sheet (cm2) 119905 is the immersion period (min) 119881H2

is volumeof evolved hydrogen gas (mL) and Δ119882 is the weight-loss(mg) ofAlmetal dissolved into the corrosivemediumTypicalplots of the gasometric and weight-loss data are shown inFigures 1 and 2 respectively These plots revealed that thevolume of H

2evolved or the loss in weight is varied linearly

with the immersion times The rate of corrosion (119877119888) can be

obtained from the slopes of the linear portions of such plotswhich corresponds to the rate constants of dissolution of Alin alkaline media obtained from either evolved hydrogen orthe weight-loss methods These values were calculated by theleast-squares method and are summarized in Table 1

32 Inhibition Efficiency ( IE) The inhibition efficienciesof the added inhibitors were calculated using the followingrelationship

IE =119877∘

119888

minus 119877

1015840

119888

119877∘

119888

times 100 (3)

where119877∘119888

and1198771015840

c are the corrosion rates of Almetal in absenceand presence of such natural polymeric inhibitors respec-tively The results are summarized in Table 2 The values ofinhibition efficiency ( IE) listed in Table 2 were foundto follow the same trend which increases with increasingthe inhibitors concentration and decreases with rising thetemperature

International Journal of Corrosion 3

0 2 4 60

10

20

30

Time (min)

ΔW

(mg)

Figure 2 A typical plot of the weight-loss versus time for corrosionof Al in alkaline media in absence of inhibitors at 30∘C [OHminus] =40mol dmminus3

Table 1 The corrosion rates (119877119888

) for corrosion of Al in alkalinemedia in absence and presence of inhibitors [OHminus] = 40 and I =40mol dmminus3 at 30∘C

[Inhibitor]mol dmminus3

00 001 002 003 004

Alginate 052 (048)lowast 033 028 022 016

Pectates 052 (048)lowast 025 020 015 011lowastCalculated from the weight-loss method

Table 2 Percentage of inhibitor efficiency ( IE) for corrosion ofAl in alkaline media in presence of inhibitors [OHminus] = 40 and I =40mol dmminus3 at 30∘C


001 002 003 004

Alginate 3654 4615 5769 6923

Pectates 5192 6154 7115 7885

33 Dependence of Corrosion Rates on [OHminus] In order toexamine the corrosion rates as a function of alkali concen-tration some experimental runs were performed at variousinitial concentrations of the alkali and constants of all otherreagents Plots of 119881H

2

gas versus time (evolved active H2)

were found to be linear in which the rate constants increasedwith increasing the [OHminus] as shown in Figure 3 This resultmeans that the corrosion rate is a function of the alkaliconcentration

34 Dependence of Corrosion Rates on Inhibitor Concentra-tions The relative rapidity and effectiveness of the hydrogenevolution method as well as its suitability for monitoring anyin situ interruption of the inhibitors with regard to the gasevolution in metalcoordinate systems have been discussedelsewhere [4 40]

0 1 2 30

2

4

6

8

10

A

B

C

Time (min)

VH2

(mL

cm2)

Figure 3 Plots of evolved 119881H2 versus time for corrosion of Al inalkaline media in absence of inhibitors at 30∘C [OHminus] (119860) = 20(119861) = 30 (119862) = 40mol dmminus3

00 08 16 240

4

8

12

16

A

B

C

Time (min)

VH2

(mL

cm2)

Figure 4 Influence of alginates as inhibitor of corrosion of Al inalkaline media [OHminus] = 40 and I = 40mol dmminus3 at 35∘C 119860absence of inhibitor 119861 003mol dmminus3 inhibitor 119862 006mol dmminus3inhibitor

The reduction in hydrogen evolution rate for dissolutionof Al metal in NaOH was found to be dependent uponthe concentration of the inhibitors which decreased withincreasing the inhibitors concentration (ALG and PEC) asshown in Table 1 and Figures 4 and 5 On the other handthe rate of hydrogen evolution was increased with rising thetemperature in either the presence or absence of inhibitorsadded


00 08 16 240

5

10

15

20V

H2

(mL

cm2)

A

B

C

Time (min)

Figure 5 Influence of pectates as inhibitor of corrosion of Al inalkaline media [OHminus] = 40 and I = 40mol dmminus3 at 35∘C 119860absence of inhibitor 119861 003mol dmminus3 inhibitor 119862 006mol dmminus3inhibitor

In view of the above aspects and the experimentalobservations a tentative corrosion mechanism based on theelectrochemical processes for dissolution of Al in NaOHmaybe suggested This mechanism can be illustrated by anodic(4)ndash(7) and cathodic (8) reactions respectively For the anodeprocess

Al +OHminus = Al(OH)ads + eminus

(4)

Al(OH)ads +OHminus

= Al(OH)2ads + e

minus

(5)

Al(OH)2ads +OH

minus

= Al(OH)3ads + e

minus

(6)

Al(OH)3ads +OH

minus

= Al(OH)minus4ads (7)

and for the cathode process

H2O + eminus = H +OHminus (8)

The overall electrochemical process is

2Al + 2OHminus + 6H2O = 2Al(OH)

4

minus

+ 3H2 (9)

The dissolution of Al metal in the anodic reaction isaccompanied by the cathodic reaction which consumesthe electrons released in the anodic process in order toform hydrogen atoms which react by combining with otheradsorbed hydrogen atoms to give bubbles ofH

2gasmolecules

at the metal surface

H +H2O + eminus = H

2+OHminus (10)

The lesser H2gas liberated from Al metal surface in

the presence of ALG or PEC inhibitors compared to theblank solution indicates that the cited inhibitors are actually

effective inhibitors for the corrosion of Al metal in alkalinemedia

Of course a little amount of the formed hydrogen atomswill remain without adsorption but it does not affect the cor-rosion processes So the rate of combination and adsorptionof hydrogen atoms is the same for all inhibitor levelsThis factmay be confirmed by the observed identical results obtainedfrom the gasometric and weight-loss techniques (Table 1)

35 Corrosion Activation Parameters Arrhenius suggestedthe famous equation that correlates the temperature variationwith rate constants (119877

119888) [41]

ln119877119888= ln119860 minus

119864=

app

119877119879

(11)

Here119860 is the frequency factor119864 =app is the apparent activationenergy 119877 is the gas constant and 119879 is the absolute tempera-ture Equation (11) predicts that plotting of ln119877

119888versus 1119879

should be linear as was experimentally observed The slopeof the line gives minus119864 =app119877119879 whereas the intercept of the linesextrapolated to (minus1119879 = 0) gives ln119860

On the other hand the changes in enthalpies (Δ119867 = ) andentropies (Δ119878 = ) of activation for the activated complexesformation in the transition states can be obtained from thetransition state theory [42]

minus ln 119877ℎ119873119879

119877119888=Δ119867=

119877119879

minusΔ119878=

119877

(12)

where ℎ is Planckrsquos constant and119873 is Avogadrorsquos numberAccording to (12) plots of minus ln(119877ℎ119873119879)119877

119888versus 1119879

gave good straight lines with intercepts on 119910 axis fromwhoseslopes and intercepts the activation parameters Δ119867 = andΔ119878= can be evaluated respectively These values were calcu-

lated using the least-squares method and are summarized inTable 3

The values of the 119864 =app for non-inhibited solutions arehigher than those of inhibited ones indicating the inhibitiveaction of influence of both ALG and PEC inhibitors on thecorrosion processes by increasing the energy barriers for thecorrosion processes emphasizing the electrostatic characterof the inhibitors adsorption on Al surface

Again the decrease of 119864 =app value with increasing theinhibitor concentration (Table 3) may be attributed to theshift of the net corrosion reaction from that on the uncoveredsurface to one involving the adsorbed sites [43] In fact onehas to take into account the effect of the frequency factor (119860)It was found that the tendency of variation in the frequencyfactor seemed to be quite similar to that in the appreciatedactivation energy A similar phenomenon has been observedelsewhere [43 44]

36 Adsorption Isotherms Adsorption isotherms providebasic information on the nature of interaction between theinhibitor and the Al metal through applying some adsorp-tion isotherm models Two main types of interaction candescribe the adsorption of inhibitors on the metal surface


Table 3 Activation parameters for corrosion of Al in alkaline media in absence and presence of some added inhibitors [OHminus] = 40 and I =40mol dmminus3

Inhibitor[Inhibitor]mol dmminus3

ParameterΔ119867=

kJmolminus1Δ119878=

Jmolminus1 Kminus1Δ119866=

kJmolminus1119864119886

=

kJmolminus1119860

molminus1 sminus1

Alginate00 5885 +6197 7731 6115 111 times 10

11

001 6661 minus3064 7574 6903 414 times 1011

003 6360 minus4410 7674 6617 871 times 1011

Pectates00 5885 +2671 7731 6115 111 times 10

11

001 6494 minus3845 7640 6751 172 times 1011

003 6148 minus5423 7764 6405 257 times 1010

Table 4 Some kinetic parameters from Langmuir isotherm model for corrosion of Al in alkaline media [OHminus] = 40 and I = 40mol dmminus3

Inhibitor Temp (∘C) Δ119866∘

ads (kJmolminus1) Slope (119899) 119870ads (dm3 molminus1) 119877

2

Alginate30 minus1966 1004 5038 gt09935 minus2074 1032 6780 gt09945 minus2183 1094 9091 gt099

Pectates30 minus2131 1042 9804 gt09935 minus2203 1006 11299 gt09945 minus2310 0984 12903 gt099

Table 5 Thermodynamic parameters of Δ119867∘ads and Δ119878∘ads forcorrosion ofAl in alkalinemedia in the absence andpresence ofALGand PEC inhibitors [OHminus] = 40 and I = 40mol dmminus3

Inhibitor ParametersΔ119867∘

ads (kJmolminus1) Δ119878∘

ads (Jmolminus1 Kminus1) 1198772

Alginate 4505 21715 gt099Pectates 2098 14191 gt099

they are physisorption and chemisorption depending on thechemical structure of the inhibitor the type of the corrosivemedium and the charge and nature of corrosive metal

In aqueous solutions the metal surface is always coveredwith adsorbed water molecules Therefore the adsorption ofinhibitor molecules from an aqueous solution is a quasisub-stituted process [45] and the inhibitors that have the abilityto be adsorbed strongly on the metal surface will hinder thedissolution reaction of the immersedmetal into the corrosivemedium The mechanism of corrosion inhibition can beexplained in terms of the adsorption behavior based on thecalculated surface coverage degrees

Generally several adsorption isotherms such as Lang-muir Freundlich Temkin Frukmin and El-Wady et alisothermmodels were postulated for graphical fitting of thesecalculated surface coverage values [46 47] Here the degreeof surface coverage (120579) for different inhibitor concentrationswas calculated from the gas evolution data using the relation-ship

120579 = 1 minus

119877∘

119888

1198771015840

119888

(13)

The correlation coefficient (1198772) can be used to determinethe best fit isotherm By far the best fit model for the

present experimental data was fitted with applying Langmuiradsorption isotherm

119862

120579

=1

119870ads+ 119862 (14)

where 120579 is the surface coverage 119862 is the inhibitor concentra-tion and119870ads is the equilibrium constant of adsorption

The value of119870ads is related to the standard free-energy ofadsorption Δ119866∘ads by the following equation [48]

ln119870ads = minus ln119862H2O minusΔ119866∘

ads119877119879

(15)

or

Δ119866∘

ads = minus119877119879 (555119870ads) (16)

where 119862H2O is the molar concentration of water expressed in

mol dmminus3 (the same as that of inhibitor concentration)As shown in Figure 6 plotting of 119862120579 against [119862] was

fairly linear for all inhibitors concentrations and differenttemperatures The slopes were found to be approximatelyunity in all cases as suggested by Langmuir adsorptionisotherm (1198772 gt 099) Also it was surprising when the resultsobtainedwere also found to verify the thermodynamicmodelof Freundlich isotherm as is shown in Figure 7

log 120579 = log119870ads + 119899 log119862 (17)

The kinetic parameters for adsorption were calculatedby the least-squares method and are summarized in Tables4 5 and 6 The values of 119870ads were found to increase withincreasing the temperature indicating that the adsorptionprocesses are endothermic in nature This trend may also


Table 6 Some kinetic parameters from Freundlich isothermmodel for corrosion of Al in alkaline media [OHminus] = 40 and I = 40mol dmminus3


ads kJmolminus1 Slope (119899) 119870ads dm3 molminus1 119877

2

Alginate30 minus738 045 036 sim09935 minus787 038 041 sim09945 minus857 030 051 sim098

Pectates30 minus815 031 048 sim09935 minus845 027 052 sim09945 minus879 025 053 sim098

000 001 002 003 004 005000

004

008

AlginatePectate

[C]

[C]120579

Figure 6 A plot of Langmuir isotherm for corrosion of Al inalkaline media at 35∘C

indicate that the inhibitor molecules are physically adsorbedon Al metal surface Again the negative values observed ofΔ119866∘

ads (Tables 4 and 6) are consistent with the spontaneity forthe adsorption processes and stability of the adsorbed layeron Al metal surface that is it may confirm the existence ofa physical adsorption mechanism In view of the correlationcoefficients (1198772) Langmuir isotherm model is the morefavorable one to fit the experimental data of the presentinvestigation

Generally the adsorption can be described by two maintypes namely chemisorptions [49] and physisorption [50]respectively Physisorption involves electrostatic interactionbetween ionic charges or dipoles on the adsorbed speciesand the electric charge at the metalsolution surface whilechemisorption involves charge sharing or charge transferprocess from the inhibitor molecules to the metal surface inorder to form a sort of covalent or coordinate bonds

It has been accepted that the values of Δ119866∘ads up to simminus20 kJmolminus1 are corresponding to the physisorption inwhichthe inhibition action is due to the electrostatic interactionbetween the charged molecules and the charged metal Onthe other hand the values which lie around minus40 kJmolminus1 orsmaller are corresponding to chemisorption process and areattributed to the charge sharing or transfer processes fromthe inhibitor molecules to the metal surface in order to form

12 15 18 2100

02

04

Alginate Pectate

log [C]

log120579

Figure 7 A plot of Freundlich isotherm for corrosion of Al inalkaline media at 35∘C

a sort of covalent or coordinate bonds [51 52] Thereforethe thermodynamic parameters obtained can be consideredas a useful tool for clarifying the adsorption behavior of theinhibitor used [53]

References

[1] G Y El-Wady I A El-Said and A S Fouda ldquoAnion surfactantsas corrosion inhibitors for aluminum dissolution in HCl solu-tionsrdquo International Journal of Electrochemical Science vol 3 pp177ndash190 2008

[2] P S Desai and S M Kapopara ldquoInhibiting effect of anisidineson corrosion of aluminium in hydrochloric acidrdquo Indian Journalof Chemical Technology vol 16 no 6 pp 486ndash491 2009

[3] G K Gomma and M H Wahdan ldquoSchiff bases as corrosioninhibitors for aluminium in hydrochloric acid solutionrdquo Mate-rials Chemistry amp Physics vol 39 no 3 pp 209ndash213 1995

[4] S Li S Chen S Lei H Ma R Yu and D Liu ldquoInvestigationon some Schiff bases as HCl corrosion inhibitors for copperrdquoCorrosion Science vol 41 no 7 pp 1273ndash1287 1999

[5] A Y El-Etre ldquoInhibition of aluminum corrosion using Opuntiaextractrdquo Corrosion Science vol 45 no 11 pp 2485ndash2495 2003

[6] M Abdallah ldquoAntibacterial drugs as corrosion inhibitors forcorrosion of aluminium in hydrochloric solutionrdquo CorrosionScience vol 46 no 8 pp 1981ndash1996 2004


[7] S S Andel Rehim H H Hassan and M A Amin ldquoCorrosioninhibition study of pure Al and some of its alloys in 10M HClsolution by impedance techniquerdquo Corrosion Science vol 46no 1 pp 5ndash25 2004

[8] P C Okafor C B Liu X Liu et al ldquoCorrosion inhibition andadsorption behavior of imidazoline salt on N80 carbon steelin CO

2

-saturated solutions and its synergism with thioureardquoJournal of Solid State Electrochemistry vol 14 no 8 pp 1367ndash1376 2010

[9] H Ashassi-Sorkhabi B Shabani B Aligholipour and DSeifzadeh ldquoThe effect of some Schiff bases on the corrosionof aluminum in hydrochloric acid solutionrdquo Applied SurfaceScience vol 252 no 12 pp 4039ndash4047 2006

[10] S S Abd El RehimM A Amin S O Moussa and A S EllithyldquoThe corrosion inhibition of aluminum and its copper alloysin 10M H

2

SO4

solution using linear-sodium dodecyl benzenesulfonate as inhibitorrdquoMaterials Chemistry and Physics vol 112no 3 pp 898ndash906 2008

[11] A S Fouda A A Al-Sarawy F S Ahmed and H M El-Abbasy ldquoCorrosion inhibition of aluminum 6063 using somepharmaceutical compoundsrdquo Corrosion Science vol 51 no 3pp 485ndash492 2009

[12] K F Khaled and M M Al-Qahtani ldquoThe inhibitive effect ofsome tetrazole derivatives towardsAl corrosion in acid solutionchemical electrochemical and theoretical studiesrdquo MaterialsChemistry and Physics vol 113 no 1 pp 150ndash158 2009

[13] A K Maayta and N A F Al-Rawashdeh ldquoInhibition of acidiccorrosion of pure aluminum by some organic compoundsrdquoCorrosion Science vol 46 no 5 pp 1129ndash1140 2004

[14] R M Hassan and I A Zaafarany ldquoKinetics of corrosioninhibition of aluminum in acidicmedia bywater-soluble naturalpolymeric pectates as anionic polyelectrolyte inhibitorsrdquoMate-rials vol 6 no 6 pp 2436ndash2451 2013

[15] B Muller and S Fischer ldquoEpoxy ester resins as corrosioninhibitors for aluminium and zinc pigmentsrdquoCorrosion Sciencevol 48 no 9 pp 2406ndash2416 2006

[16] B Muller and T Schmelich ldquoHigh-molecular weight styrene-maleic acid copolymers as corrosion inhibitors for aluminiumpigmentsrdquo Corrosion Science vol 37 no 6 pp 877ndash883 1995

[17] B Muller C Oughourlian and M Schubert ldquoAmphiphiliccopolymers as corrosion inhibitors for zinc pigmentrdquoCorrosionScience vol 42 no 3 pp 578ndash584 2000

[18] B Muller ldquoPolymeric corrosion inhibitors for aluminum pig-mentrdquo Reactive and Functional Polymers vol 39 no 2 pp 165ndash177 1999

[19] A M Abdel-Gaber E Khamis H Abo-ElDahab and S AdeelldquoInhibition of aluminium corrosion in alkaline solutions usingnatural compoundrdquo Materials Chemistry and Physics vol 109no 2-3 pp 297ndash305 2008

[20] M A Amin S S A EI-Rehim E E F El-Sherbini O AHazzazi and M N Abbas ldquoPolyacrylic acid as a corrosioninhibitor for aluminium in weakly alkaline solutions Part Iweight loss polarization impedance EFM and EDX studiesrdquoCorrosion Science vol 51 no 3 pp 658ndash667 2009

[21] I A Zaafarany ldquoCorrosion inhibition of aluminum in aqueoussolutions by alginate and pectate water-soluble natural polymeranionic polyelectrolytesrdquo Portugaliae Electrochimica Acta vol30 no 6 pp 419ndash426 2012

[22] M I Abdel-Hamid K S Khairou and R M Hassan ldquoKineticsand mechanism of permanganate oxidation of pectin polysac-charide in acid perchlorate mediardquo European Polymer Journalvol 39 no 2 pp 381ndash387 2003

[23] R M Hassan ldquoAlginate polyelectrolyte ionotropic gels XIVKinetics and mechanism of formation of intermediate complexduring the oxidation of alginate polysaccharide by alkaline per-manganate with a spectrophotometric evidence of manganate(VI) transient speciesrdquo Journal of Polymer Science A vol 31 no1 pp 51ndash59 1993

[24] K S Khairou and R M Hassan ldquoPectate polyelectrolyteionotropic gels 1 Kinetics and mechanisms of formation ofmanganate (VI)-pectate intermediate complex during the oxi-dation of pectate polysaccharide by alkaline permanganaterdquoEuropean Polymer Journal vol 36 no 9 pp 2021ndash2030 2000

[25] R M Hassan M H Wahdan and A Hassan ldquoKineticsand mechanism of sol-gel transformation on polyelectrolytesof nickel alginate ionotropic membranesrdquo European PolymerJournal vol 24 no 3 pp 281ndash283 1988

[26] R M Hassan S A El-Shatoury M A Mousa and A HassanldquoKinetics and mechanism of sol-gel transformation for poly-electrolytes of capillary copper alginate ionotropicmembranesrdquoEuropean Polymer Journal vol 24 no 12 pp 1173ndash1175 1988

[27] R M Hassan ldquoAlginate polyelectrolyte ionotropic gels-partIII Kinetics of exchange of chelated divalent transition metalions especially cobalt(II) and copper(II) by hydrogen ions incapillary ionotropicmetal alginate polymembrane gelsrdquo Journalof Materials Science vol 26 no 21 pp 5806ndash5810 1991

[28] R M Hassan ldquoAlginate polyelectrolyte ionotropic gels-partII Kinetics and mechanism of exchange of chelated nickel(II) by hydrogen ions in capillary ionotropic nickel alginatepolymembrane gel complexrdquo Journal of Materials Science vol28 no 2 pp 384ndash388 1993

[29] R M Hassan A Awad and A Hassan ldquoSeparation of metalalginate ionotropic gels to polymembranes with special evi-dence on the position of chelation in copper alginate complexrdquoJournal of Polymer Science A vol 29 no 11 pp 1645ndash1648 1991

[30] R M Hassan ldquoKinetics and mechanism of sol-gel trans-formation on polyelectrolytes of nickel alginate ionotropicmembranesrdquo Polymer International vol 31 pp 81ndash86 1993

[31] R M Hassan M T Makhlouf and S A El-Shatoury ldquoAlginatepolyelecrtolyte ionotropic gels Part IX diffusion control effectson the relaxation time of sol-gel transformation for transition-divalent metal alginate ionotropic gel complexesrdquo Colloid ampPolymer Science vol 270 no 12 pp 1237ndash1242 1992

[32] RMHassan ldquoInfluence of frequency on electrical properties ofacid and trivalent metal alginate ionotropic gels A Correlationbetween strength of chelation and stability of polye1ectrolyregelsrdquo High Performance Polymers vol 1 pp 275ndash284 1989

[33] R M Hassan M T Makhlouf A M Summan and AAwad ldquoInfluence of frequency on specific conductance ofpolyelectrolyte gels with special correlation between strengthof chelation and stability of divalent metal alginate ionotropicgelsrdquo European Polymer Journal vol 25 no 10 pp 993ndash9961989

[34] R M Hassan ldquoAlginate polyelectrolyte ionotropic gels 7Physico-chemical studies on silver(I) alginate complex withspecial attention to the electrical conductance and geometricalstructurerdquo Colloids and Surfaces C vol 60 pp 203ndash212 1991

[35] R M Hassan Y Ikeda and H Tomiyasu ldquoAlginate polyelec-trolyte ionotropic gels-part XV Physicochemical properties ofuranyl alginate complex especially the chemical equilibriumand electrical conductivity related to the coordination geom-etryrdquo Journal of Materials Science vol 28 no 19 pp 5143ndash51471993


[36] K S Khairou and R M Hassan ldquoTemperature-dependence ofthe electrical conductivity for cross-linked mono- and divalentmetal-alginate complexesrdquo High Performance Polymers vol 14no 1 pp 93ndash102 2002

[37] I A Zaafarany K S Khairou and R M Hassan ldquoPhysico-chemical studies on some cross-linked trivalent metal-alginatecomplexes especially the electrical conductivity and chemicalequilibrium related to the coordination geometryrdquoHigh Perfor-mance Polymers vol 22 no 1 pp 69ndash81 2010

[38] K S Khairou R M Hassan and A M Shaker ldquoNovel synthe-sis of diketocarboxymethyl-celluose as bipolymer precursorsrdquoJournal of Applied Polymer Science vol 85 no 5 pp 1019ndash10232002

[39] L Z Vorkapic D M Drazic and A R Despic ldquoCorrosion ofpure and amalgamated zinc in concentrated alkali hydroxidesolutionsrdquo Journal of the Electrochemical Society vol 121 no 11pp 1385ndash1392 1974

[40] M M Solomon S A Umoren I I Udosoro and A PUdoh ldquoInhibitive and adsorption behaviour of carboxymethylcellulose on mild steel corrosion in sulphuric acid solutionrdquoCorrosion Science vol 52 no 4 pp 1317ndash1325 2010

[41] K J Laidler Reaction Kinetics vol 1 Pergmon Press New YorkNY USA 1st edition 1963

[42] S Glasstone K J Ladiler and H EyringTheTheory of the RateProcess McGraw-Hill New York NY USA 1941


[44] S A Ali A M El-Shareef R F Al-Ghamdi and M T SaeedldquoThe isoxazolidines the effects of steric factor and hydrophobicchain length on the corrosion inhibition of mild steel in acidicmediumrdquoCorrosion Science vol 47 no 11 pp 2659ndash2678 2005

[45] H Keles M Keles I Dehri and O Serindag ldquoAdsorptionand inhibitive properties of aminobiphenyl and its Schiff baseon mild steel corrosion in 05M HCl mediumrdquo Colloids andSurfaces A vol 320 no 1ndash3 pp 138ndash145 2008

[46] M Christov and A Popova ldquoAdsorption characteristics of cor-rosion inhibitors from corrosion ratemeasurementsrdquoCorrosionScience vol 46 no 7 pp 1613ndash1620 2004

[47] E E Oguzie ldquoCorrosion inhibition of aluminium in acidicand alkaline media by Sansevieria trifasciata extractrdquo CorrosionScience vol 49 no 3 pp 1527ndash1539 2007

[48] M A Amin Q Mohsen and O A Hazzazi ldquoSynergistic effectof I- ions on the corrosion inhibition of Al in 10M phosphoricacid solutions by purinerdquoMaterials Chemistry and Physics vol114 no 2-3 pp 908ndash914 2009

[49] S Bilgic and M Sahin ldquoThe corrosion inhibition of austeniticchromium-nickel steel in H

2

SO4

by 2-butyn-1-olrdquo MaterialsChemistry and Physics vol 70 no 3 pp 290ndash295 2001

[50] A Yurt S Ulutas and H Dal ldquoElectrochemical and theoreticalinvestigation on the corrosion of aluminium in acidic solutioncontaining some Schiff basesrdquo Applied Surface Science vol 253no 2 pp 919ndash925 2006

[51] E A Noor and A H Al-Moubaraki ldquoThermodynamicstudy of metal corrosion and inhibitor adsorptionprocesses in mild steel1-methyl-4[4rsquo(-X)-styryl pyridiniumiodideshydrochloric acid systemsrdquo Materials Chemistry andPhysics vol 110 no 1 pp 145ndash154 2008

[52] A W Adamson Physical Chemistry and Surface Wiely NewYork NY USA 1990

[53] S A Umoren M M Solomon I I Udosoro and A P UdohldquoSynergistic and antagonistic effects between halide ions andcarboxymethyl cellulose for the corrosion inhibition of mildsteel in sulphuric acid solutionrdquo Cellulose vol 17 no 3 pp 635ndash648 2010

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



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NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


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MaterialsJournal of


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materials


Journal ofNanomaterials


and geometrical configuration of the inhibitors used in theadsorption process as well as the influence of the nature ofthe medium on the corrosion mechanism

2 Experimental

21 Materials All materials used were of analytical gradeDoubly distilled conductivity water was used in all prepara-tions The temperature was controlled within plusmn01∘C

Sodium alginate (ALG) and sodium pectate (PEC)were purchased from Fluka and were used withoutfurther purification The degree of substitution was foundto be 43mmol gminus1 (091molmolminus1) and 41mmol gminus1(082molmolminus1) for alginates and pectates respectively

Aluminum metal used was of 9998 purity (VentronCrop Osaka Japan)

22 Preparation of Inhibitor Sols Sols of alginate and pectatepolysaccharides were prepared as described earlier [21 22]This process was performed by stepwise addition of the pow-der reagent to bidistilled water whilst rapidly and vigorouslystirring the solutions to avoid the formation of lumps whichswell with difficulty Then the prepared alginate or pectatesols were left at room temperature (25∘C) for about 24 h inorder to become air-bubbles-free being before used

23 Measurement Techniques Although the weight-losstechnique is the most employed method to acquire the cor-rosion rate data for metal coupons at natural environmentalcorrosion tests it makes the corrosion rate obtained a long-term average that is it needs a long-time immersion There-fore gasometric method is usually preferred for assessingthe inhibitive performance in case of short-time immersionof the corrosive metals in acidic or alkaline solutions as inthe cited work The technique was the same as describedelsewhere [18] The course of reaction was followed bymeasuring the evolved hydrogen gas as a function of time

Some kinetic measurements were performed using theclassical weight-loss method [1 13 39 40] in order to checkthe reproducibility of the gasometric data obtained Fortu-nately the results obtained for the corrosion rates in bothtechniqueswere found to be correlatedwith each otherwithinexperimental errors (plusmn5) This fact may indicate the repro-ducibility of the results obtained by the gasometric method

All experiments were repeated using different concentra-tions of NaOH and inhibitors at various temperatures Thecited results were at least an average of four experimentalruns The corrosion medium was not stirred during the testThe experimental data obtainedwere found towell agree withthat reported earlier (within experimental errors plusmn5) [21]

3 Results and Discussions

31 Hydrogen Evolution and Weight-Loss Measurements Thevolume of the evolved H

2gas (or the loss in Al weight) as

a function of time may be taken as the rate of dissolution

0 1 2 30

2

4

6

Time (min)

VH2

(mL

cm2)

Figure 1 A typical plot of the evolved119881H2 versus time for corrosionof Al in alkaline media in absence of inhibitors at 30∘C [OHminus] =40mol dmminus3

of aluminum in sodium hydroxide and can be expressedrespectively by

119877119888=

119881H2

119871 sdot 119905

(1)

119877119888=Δ119882

119871 sdot 119905

(2)

where119877119888is the corrosion rate 119871 is the surface area of Almetal

sheet (cm2) 119905 is the immersion period (min) 119881H2

is volumeof evolved hydrogen gas (mL) and Δ119882 is the weight-loss(mg) ofAlmetal dissolved into the corrosivemediumTypicalplots of the gasometric and weight-loss data are shown inFigures 1 and 2 respectively These plots revealed that thevolume of H

2evolved or the loss in weight is varied linearly

with the immersion times The rate of corrosion (119877119888) can be

obtained from the slopes of the linear portions of such plotswhich corresponds to the rate constants of dissolution of Alin alkaline media obtained from either evolved hydrogen orthe weight-loss methods These values were calculated by theleast-squares method and are summarized in Table 1

32 Inhibition Efficiency ( IE) The inhibition efficienciesof the added inhibitors were calculated using the followingrelationship

IE =119877∘

119888

minus 119877

1015840

119888

119877∘

119888

times 100 (3)

where119877∘119888

and1198771015840

c are the corrosion rates of Almetal in absenceand presence of such natural polymeric inhibitors respec-tively The results are summarized in Table 2 The values ofinhibition efficiency ( IE) listed in Table 2 were foundto follow the same trend which increases with increasingthe inhibitors concentration and decreases with rising thetemperature


0 2 4 60

10

20

30

Time (min)

ΔW

(mg)





00 001 002 003 004

Alginate 052 (048)lowast 033 028 022 016




001 002 003 004

Alginate 3654 4615 5769 6923

Pectates 5192 6154 7115 7885


2




0 1 2 30

2

4

6

8

10

A

B

C

Time (min)

VH2

(mL

cm2)


00 08 16 240

4

8

12

16

A

B

C

Time (min)

VH2

(mL

cm2)




00 08 16 240

5

10

15

20V

H2

(mL

cm2)

A

B

C

Time (min)




(4)

Al(OH)ads +OHminus

= Al(OH)2ads + e

minus

(5)

Al(OH)2ads +OH

minus

= Al(OH)3ads + e

minus

(6)

Al(OH)3ads +OH

minus






4

minus

+ 3H2 (9)


2gasmolecules


H +H2O + eminus = H

2+OHminus (10)






119888) [41]

ln119877119888= ln119860 minus

119864=

app

119877119879

(11)


119888versus 1119879



minus ln 119877ℎ119873119879

119877119888=Δ119867=

119877119879

minusΔ119878=

119877

(12)


119888versus 1119879









ParameterΔ119867=




=

kJmolminus1119860

molminus1 sminus1

Alginate00 5885 +6197 7731 6115 111 times 10

11

001 6661 minus3064 7574 6903 414 times 1011

003 6360 minus4410 7674 6617 871 times 1011

Pectates00 5885 +2671 7731 6115 111 times 10

11

001 6494 minus3845 7640 6751 172 times 1011

003 6148 minus5423 7764 6405 257 times 1010




2











120579 = 1 minus

119877∘

119888

1198771015840

119888

(13)



119862

120579

=1

119870ads+ 119862 (14)




ads119877119879

(15)

or

Δ119866∘

ads = minus119877119879 (555119870ads) (16)




log 120579 = log119870ads + 119899 log119862 (17)






2



000 001 002 003 004 005000

004

008

AlginatePectate

[C]

[C]120579






12 15 18 2100

02

04

Alginate Pectate

log [C]

log120579



References










2




2

SO4










































2

SO4













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0 2 4 60

10

20

30

Time (min)

ΔW

(mg)





00 001 002 003 004

Alginate 052 (048)lowast 033 028 022 016




001 002 003 004

Alginate 3654 4615 5769 6923

Pectates 5192 6154 7115 7885


2




0 1 2 30

2

4

6

8

10

A

B

C

Time (min)

VH2

(mL

cm2)


00 08 16 240

4

8

12

16

A

B

C

Time (min)

VH2

(mL

cm2)




00 08 16 240

5

10

15

20V

H2

(mL

cm2)

A

B

C

Time (min)




(4)

Al(OH)ads +OHminus

= Al(OH)2ads + e

minus

(5)

Al(OH)2ads +OH

minus

= Al(OH)3ads + e

minus

(6)

Al(OH)3ads +OH

minus






4

minus

+ 3H2 (9)


2gasmolecules


H +H2O + eminus = H

2+OHminus (10)






119888) [41]

ln119877119888= ln119860 minus

119864=

app

119877119879

(11)


119888versus 1119879



minus ln 119877ℎ119873119879

119877119888=Δ119867=

119877119879

minusΔ119878=

119877

(12)


119888versus 1119879









ParameterΔ119867=




=

kJmolminus1119860

molminus1 sminus1

Alginate00 5885 +6197 7731 6115 111 times 10

11

001 6661 minus3064 7574 6903 414 times 1011

003 6360 minus4410 7674 6617 871 times 1011

Pectates00 5885 +2671 7731 6115 111 times 10

11

001 6494 minus3845 7640 6751 172 times 1011

003 6148 minus5423 7764 6405 257 times 1010




2











120579 = 1 minus

119877∘

119888

1198771015840

119888

(13)



119862

120579

=1

119870ads+ 119862 (14)




ads119877119879

(15)

or

Δ119866∘

ads = minus119877119879 (555119870ads) (16)




log 120579 = log119870ads + 119899 log119862 (17)






2



000 001 002 003 004 005000

004

008

AlginatePectate

[C]

[C]120579






12 15 18 2100

02

04

Alginate Pectate

log [C]

log120579



References










2




2

SO4










































2

SO4













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




00 08 16 240

5

10

15

20V

H2

(mL

cm2)

A

B

C

Time (min)




(4)

Al(OH)ads +OHminus

= Al(OH)2ads + e

minus

(5)

Al(OH)2ads +OH

minus

= Al(OH)3ads + e

minus

(6)

Al(OH)3ads +OH

minus






4

minus

+ 3H2 (9)


2gasmolecules


H +H2O + eminus = H

2+OHminus (10)






119888) [41]

ln119877119888= ln119860 minus

119864=

app

119877119879

(11)


119888versus 1119879



minus ln 119877ℎ119873119879

119877119888=Δ119867=

119877119879

minusΔ119878=

119877

(12)


119888versus 1119879









ParameterΔ119867=




=

kJmolminus1119860

molminus1 sminus1

Alginate00 5885 +6197 7731 6115 111 times 10

11

001 6661 minus3064 7574 6903 414 times 1011

003 6360 minus4410 7674 6617 871 times 1011

Pectates00 5885 +2671 7731 6115 111 times 10

11

001 6494 minus3845 7640 6751 172 times 1011

003 6148 minus5423 7764 6405 257 times 1010




2











120579 = 1 minus

119877∘

119888

1198771015840

119888

(13)



119862

120579

=1

119870ads+ 119862 (14)




ads119877119879

(15)

or

Δ119866∘

ads = minus119877119879 (555119870ads) (16)




log 120579 = log119870ads + 119899 log119862 (17)






2



000 001 002 003 004 005000

004

008

AlginatePectate

[C]

[C]120579






12 15 18 2100

02

04

Alginate Pectate

log [C]

log120579



References










2




2

SO4










































2

SO4













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






ParameterΔ119867=




=

kJmolminus1119860

molminus1 sminus1

Alginate00 5885 +6197 7731 6115 111 times 10

11

001 6661 minus3064 7574 6903 414 times 1011

003 6360 minus4410 7674 6617 871 times 1011

Pectates00 5885 +2671 7731 6115 111 times 10

11

001 6494 minus3845 7640 6751 172 times 1011

003 6148 minus5423 7764 6405 257 times 1010




2











120579 = 1 minus

119877∘

119888

1198771015840

119888

(13)



119862

120579

=1

119870ads+ 119862 (14)




ads119877119879

(15)

or

Δ119866∘

ads = minus119877119879 (555119870ads) (16)




log 120579 = log119870ads + 119899 log119862 (17)






2



000 001 002 003 004 005000

004

008

AlginatePectate

[C]

[C]120579






12 15 18 2100

02

04

Alginate Pectate

log [C]

log120579



References










2




2

SO4










































2

SO4













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials







2



000 001 002 003 004 005000

004

008

AlginatePectate

[C]

[C]120579






12 15 18 2100

02

04

Alginate Pectate

log [C]

log120579



References










2




2

SO4










































2

SO4













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






2




2

SO4










































2

SO4













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials


















2

SO4













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



Documents

Research Article A Revisit to the Corrosion Inhibition of Aluminum in Aqueous …downloads.hindawi.com › journals › ijc › 2013 › 508596.pdf · 2019-07-31 · A Revisit to