EffectsofAlloyingElements(Cr,Mn)onCorrosionPropertiesof ...downloads.hindawi.com/journals/amse/2018/7638274.pdf · 18Mn5Cr>18Mn>REF, which corresponds with the change of the mean

Research ArticleEffects of Alloying Elements (Cr Mn) on Corrosion Properties ofthe High-Strength Steel in 35 NaCl Solution

Bomi Kim 1 Soojin Kim 2 and Heesan Kim 1

1Department of Materials Science and Engineering Hongik University 2639 Sejong-ro Jochiwon-eup Sejong 339-701Republic of Korea2University of Alabama School of Medicine 510 20th St S Birmingham AL 35210 USA

Correspondence should be addressed to Heesan Kim heesan1118gmailcom

Received 30 August 2017 Revised 23 October 2017 Accepted 31 October 2017 Published 15 February 2018

Academic Editor Marıa V Biezma

Copyright copy 2018 Bomi Kim et al is 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

Effects of chromium and manganese as alloying elements on corrosion resistance of carbon steel were examined using evaluationof corrosion resistance in 60degC NaCl solution with a weight loss test polarization test analysis of rust with X-ray diffractometerRaman spectroscopy transmission electron microscopy energy dispersive spectroscopy and electron energy loss spectroscopye weight loss behavior conformed to a typical parabolic law and the oxidation state of iron in rust was higher along the fastpathway but was disproportionate to the distance from the alloyAR interface It suggests that the corrosion process of the alloyswas controlled by transport of oxygen to the rust layer e improvements in corrosion resistance of 18Mn and 18Mn5Cr resultedfrom both the refinement of grain in adherent rust (AR) and the increase of the amounts of goethite in nonadherent rust (NAR) bychromium andmanganese Especially the effectiveness of chromium on corrosion resistance was also related to the refinements ofgrain in AR and the amounts of goethite in NAR e Tafel extrapolation method was inadequate to measure the instantaneouscorrosion rate of steels with various alloying elements and immersion periods because of the difference in electrochemicalreduction rates of rust depending on its constituent

1 Introduction

Highmanganese steels with high strength and toughness weredeveloped to satiate the need for a material with superbphysical properties in response to energy crisis and carbondioxide release restriction [1] However even recently rele-vant studies on the effects of manganese on corrosion re-sistance of steel have been comparatively minimal [2ndash5]Particularly the effects of manganese on corrosion resistanceof steel during the exposure to chloride-containing envi-ronments have been reported inconsistently [4 6ndash12]

In a previous study Melchers [13 14] proposeda model on the corrosion process of carbon steel Beforemicrobiological-induced corrosion (MIC) or pitting corro-sion does not occur the model consists of two stagesdepending on the rate-determining step reactions on itsmetal surface for the first stage and diffusion of oxygenthrough rust for the second stage Because the model remainsin the second stage for the most of the total exposure period

we believe that corrosion resistance of carbon steels duringa long-term exposure greatly depends on the rust as it servesas a medium for oxygen penetration e long-term exposuretest has shown that the corrosion rates for the rust compo-nents are less than 001mmyr as shown in (1) [15 16]

αclowastgt 1

ors + βclowastlt 05

(1)

where α s c and β are the mass concentrations of goethitespinel oxide lepidocrocite and akaganeite respectively andclowast is the total of s c and β e first equation demonstratesthe effect of the amount of ultrafine-grained goethite on therust protectiveness e second equation illustrates thepenetration of corrosive species through the defects inakaganeite and spinel oxide [15 17 18]

HindawiAdvances in Materials Science and EngineeringVolume 2018 Article ID 7638274 13 pageshttpsdoiorg10115520187638274

In general the transport of oxygen through rust dependson its grain size crystal structure chemical stability andporosity [19ndash24] which explains the dependency of corrosionresistance on iron oxide or oxyhydroxide According to theMelchers model during the initial state of the first stage steelsare oxidized to produce various forms of dissolved ferrous ion orprecipitated ferrous hydroxidee various forms of ferrous ionare chemically or electrochemically oxidized by oxygen toproduce different types of ferric oxyhydroxide maghemite orhematite With the elapsed time the thickened rust layer im-pedes the transport of oxygen to the steel surface During thisperiod various forms of ferric oxyhydroxide may reduce tomagnetite [25 26] incorporation of ferrous ion into ferricoxyhydroxide [27] slow oxidation of ferrous hydroxide via greenrust (GR) [28] or reaction of the dissolved ferric oxyhydroxidewith dissolved ferrous hydroxide [29 30] e first processoccurs in rust and the other processes occur at the rustsolutioninterface or at rust near the solution As an alloying elementmanganese not only impedes the formation ofmagnetite [31 32]but also encourages the formation of refined goethite Chro-mium hinders magnetitersquos nucleation [33] and growth [34]while it promotes the nucleation [33] and growth [35] of goethiteand refinement of grain [36] Both manganese and chromiumimprove corrosion resistance of steel however chromium hasa greater effect than manganese [36]

e effects of manganese and chromium on corrosionresistance [37] of high manganese steels were studied byexamining rust properties with X-ray diffraction (XRD)Raman spectroscopy energy dispersive spectroscopy (EDS)[4 5] and electron energy loss spectroscopy (EELS) adjunctto transmission electron microscopy (TEM)

2 Experimental Procedure

21 Preparation of Specimen e ingots (API60 18Mn and18Mn5Cr) with chemical compositions listed in Table 1were cast to examine the effects of corrosion resistanceof carbon steel on manganese and chromium API60 wasused as a reference material and hereafter named ldquoREFrdquo25 kg ingots were heat treated at 1150degC for 15 hoursunder an argon atmosphere and hot rolled to 45mm Bothsurfaces of the plate were mill-machined to 3mm thick-ness in order to remove the scale formed during theheat treatment en the 3mm thick plates were cut into2 cm times 1 cm times 04 cm coupons for an immersion test and1 cm times 1 cm times 04 cm coupons for a polarization test re-spectively All the surfaces were wet grounded with suc-cessive grade silicon carbide papers from 200 to 600 gritdegreased with acetone rinsed with ethanol blow-driedand finally kept in a desiccator

22 Evaluation of Corrosion Resistance e weight loss testand polarization test were conducted to evaluate corrosionresistance of the experimental alloys e tests were carried in35 NaCl aqueous solution at a constant temperature of60degC During the immersion test the coupons were supportedon cradlesmdasha glass cradle with protrusionsmdashto minimize thecradle-couple contact area In each capped vessel eachcoupon was immersed in 200mL of 35 NaCl solutionImmersion periods were 1 7 14 28 and 56 days for REF18Mn and 18Mn5Cr respectively On every 7th day thesolution was replaced with a fresh solution tomaintain the pHof the solution within 02 For the weight loss measurementsthe rust formed on the coupon was removed and the exposedcoupon was immersed in a hydrochloric acid inhibited withhexamethylenetetramine (0025M C6H12N4+ 543M HCl) atroom temperature in an ultrasonic bath for 5ndash10 minutesaccording to ASTMG1 [38] e weight measurement resultswere used to calculate the weight at an immersion time andmean weight loss rate as shown in

Mean weight loss rate ti( 1113857 ΔW ti( 1113857minusΔW timinus1( 1113857

ti minus timinus1 (2)

where ΔW(ti) is the weight loss per surficial area at im-mersion time ti

e immersion test was repeated twice under the samecondition for reproducibility If the results showed highdeviations the immersion test was repeated untilcrediblereliable data were obtained

e cathodic polarization test was conducted to measureinstantaneous corrosion rates (icorr) [39] and the anodicpolarization test was performed to observe corrosion be-haviors To prepare a working electrode the square couponswere embedded in epoxy resin [37] with an exposure area of1 cm2 wet grounded with 600 grit silicon carbide papersrinsed with ethanol dried and stored in a desiccator Asaturated calomel electrode (SCE) and a platinummesh wereused as a reference electrode and a counter electrode re-spectively e mounted coupons from 1-day and 56-dayimmersion in the chloride solution were anodically or ca-thodically polarized by a corrosion potential at the scan rateof 20mVmin By linearly fitting the polarization curvesaround the potentials by 100mV lower than corrosionpotentials cathodic Tafel slopes (βc) were obtained as well asinstantaneous corrosion rates

23 Analysis of Rust At the end of 56-day immersion thecoupons with their vessels were placed in the ultrasonic bathfor 15ndash20 seconds to remove nonadherent rusts (NARs) andthen the coupons were extracted e NARs were filtrated

Table 1 Chemical composition of the experimental alloys

Name Phase(s)Chemical composition ( wt)

C Mn Cr Ni FeREF(API60) α+ bainite 0067 16 002 02 Balance18Mn c 06 184 lt0005 lt0005 Balance18Mn5Cr c 06 185 51 lt0005 Balance

2 Advances in Materials Science and Engineering

washed with distilled water to remove chloride and dried at50degC in an oven for 1 hour Later all the rusts were groundedinto a homogeneous powder mixturee extracted couponswere also washed and dried with the same procedure as theNARs in order to analyze all the adherent rusts (ARs) whichwere still intact with the coupons after the ultrasonic bathX-ray diffraction and Raman spectroscopy were performedto analyze NARs while XRD TEM-EDS and EELS wereconducted to analyze ARs

e XRDmeasurements of the NARs were performed ona diffractometer (Digaku Dmax-3A model) equipped withCu (Kα) for both qualitative and quantitative analyses escans were done in the range of 2θ between 10deg and 90deg ata rate of 2 degreesmin For the qualitative analysis 85 ofthe entire NARs and the reference oxides listed in Table 2were mixed with 15 of zinc oxide Among the referencesamples in Table 2 magnetite hematite goethite and lep-idocrocite were purchased and the others were synthesized[22] For quantitative analysis zinc oxide was mixed to serveas a reference intensity en to quantitatively analyze theNARs 85 of several mixtures of the known amounts ofoxides listed in Table 2 were mixed with 15 of zinc oxidefollowing the internal standard method [40] From the XRDmeasurements the intensities of iron oxides were expressedas a function of concentration In terms of the qualitativeanalysis of the ARs XRD measurement was performedunder the same conditions as mentioned above Twomodeswere used to show phase distributions along the depthdirection where one is a normal mode and the other isa thin film mode In the thin film mode the glance anglewas fixed to 1deg e coupons on which ARs were formedwere used without an additional preparation for XRDmeasurements

e Raman spectra of pellets made from the powderwere measured in a Raman II-Senterra (Bruker) It was

configured with a microscope of 50x magnification eRaman spectroscopy was excited using a laser (7850 nm)with a nominal maximum output power of 1mW for 20seconds to avoid any internal structure modification ofthe samples e Raman spectra of the iron oxides listed inTable 2 were measured and summarized in Table 3 to quali-tatively analyze the NARs

e ARs were analyzed by scanning transmission elec-tron microscopy (STEM JEM-ARM200F) and their com-positions grain sizes crystal structures and oxidation stateswithin 1 μm far away from an interface between the alloy andthe AR were examined With the thinned sample preparedby a focused ion beam (FIB) AR chemical composition wasanalyzed by energy X-ray dispersive spectroscopy (EDS) thecrystal structure and grain size were analyzed by selectedarea electron diffraction (SAED) and the oxidation state ofiron was analyzed by electron energy loss spectroscopy(EELS) according to (3) [41]

Oxidation state of ironpropI of Fe L3

I of Fe L2 (3)

where I of Fe Li is the integral intensity of the Fe Li edgepeak

3 Results

31 Effect of Alloying Elements on Corrosion ResistanceFigure 1 provides both weight loss and mean weight loss ratewith immersion time of all the experimental alloys in 35NaCl solution at 60degC In all the alloys weight loss increasedwith immersion time but the mean weight loss rate de-creased which is referred as a typical parabolic behaviorhereafter In addition chromium and manganese asalloying elements showed reduced mean weight loss rates

Table 2 Summaries on the commercial companies and synthetic methods of iron oxides used for the standard Raman spectra

Iron oxide Source RemarksMagnetite High Purity Chemicals Powder lt1 μm gt99Maghemite (c-Fe2O3) [22] PowderHematite (α-Fe2O3) High Purity Chemicals Powder lt1 μm gt99Goethite (α-FeOOH) Rare Metallic Co Ltd Powder gt99Akaganeite (β-FeOOH) [22] PowderLepidocrocite (c-FeOOH) High Purity Chemicals Powder gt99

Table 3 Summary on the peaks observed from the Raman spectra of standard samples of iron rust

Standard samplePeak positionscmminus1 (relative intensity)

Remarks1st 2nd 3rd 4th 5th

Magnetite 286 (100) 396 (54) 222 (50) 640 (41)lowast 475 (22) lowastWideMaghemite (c-Fe2O3) 286 (100) 396 (54) 222 (50) 640 (41)lowast 475 (22) lowastWide peak at 710Hematite (α-Fe2O3) 292 (100) 224 (54) 410 (44) 612 (24) 494 (11) mdashGoethite (α-FeOOH) 386 (100) 301 (29) 548 (17) 482 (16) 245 (13) mdashAkaganeite (β-FeOOH) 390 (100)lowast 310 (87)lowast 495 (26) 540 (22) mdash lowastWideLepidocrocite (c-FeOOH) 250 (100) 378 (57) 530 (55) 347 (43) 308 (23) mdash

Advances in Materials Science and Engineering 3

during the immersion period while chromium improvedcorrosion resistance

e anodic polarization curves in Figure 2(a) and cor-rosion potentials in Table 4 show that corrosion potentialswere ennobled with immersion and anodic current densitiesat the range of potential between corrosion potentials andminus01 VSCE were reduced with immersion time ese resultsindicate that the decreased corrosion rate with immersionperiod in Table 4 is caused by the formation of rust resultingin the change of anodic current density In addition theratio of anodic currents at two dishyerent immersion periods

(1 day and 56 days) was reduced in the following order18Mn5Crgt 18MngtREF which corresponds with thechange of the mean weight loss rate shown in Figure 1(b)Hence the results on the immersion test and polarizationtest suggest that both chromium and manganese aid to formmore protective rust and retard the penetration of corrosivespecies such as oxygen [36] into the rust layermdasha controllingstep for corrosion Furthermore the result corresponds tothe corrosion mechanism proposed by Melchers [13] thatduring the second stage the corrosion rate of carbon steel iscontrolled by the migration rate of corrosive species through

0 10 20 30 40 50 60

000

001

002W

eigh

t los

s (gc

mminus2

)

Exposure time (days)

REF18Mn18Mn5Cr

(a)

0 10 20 30 40 50 6000

20 times 10minus4

40 times 10minus4

60 times 10minus4

80 times 10minus4

10 times 10minus3

12 times 10minus3

14 times 10minus3

16 times 10minus3

18 times 10minus3

Mea

n w

eigh

t los

s rat

e (gc

mminus2

dminus1 )


REF18Mn18Mn5Cr

(b)

Figure 1 Weight loss versus time curves (a) and average weight loss rate versus time curves (b) of experimental alloys immersed in 35NaCl solution at 60degC

10

times 10

minus7

10

times 10

minus6

10

times 10

minus5

10

times 10

minus4

10

times 10

minus3

10

times 10

minus2

10

times 10

minus1

minus080

ndash060

minus040

ndash020

000

020

040

Pote

ntia

l V

SCE

Current densityAcmminus2

REF-1dREF-56d18Mn-1d

18Mn-56d18Mn5Cr-1d18Mn5Cr-56d

(a)

REF-56d18Mn-1d


10 times

10minus

7

10 times

10minus

6

10 times

10minus

5

10 times

10minus

4

10 times

10minus

3

ndash110

ndash100

ndash090

ndash080

ndash070

ndash060

minus050

Pote

ntia

l V

SCE

Current densityAcmndash2

REF-1d

(b)

Figure 2 Anodic (a) and cathodic (b) polarization curves of experimental alloys in 35 NaCl solution at 60degC


rust erefore the relationship between the alloying ele-ment and rust will be discussed based on the results of therust analysis in Sections 33 and 34

32 Eect of Alloying Elements on Cathodic PolarizationCurve Cathodic polarization tests were also conducted inorder to conrm the eshyectiveness of the Tafel extrapolation

method in evaluating the corrosion rate Figure 2(b) showsthat cathodic current densities for all the alloys increasedwith immersion unexpectedly e increase of the cathodiccurrent density resulted from the involvement of electro-chemical reaction of rust [4 42 43] However the eshyects ofelectrochemical reduction of rust on both the Tafel slope andthe corrosion rate induced from Tafel extrapolation weredishyerent among both alloys and immersion periods On the

Table 4 Summaries on corrosion potentials Tafel slopes and corrosion rates of the experimental alloys from analysis of cathodic po-larization curves in Figure 2(b)

AlloysImmersion time

1 day 56 daysCorros pot (VSCE) Tafel slope (βc) icorr (μAcm2) Corros pot (VSCE) Tafel slope (βc) icorr (μAcm2)

REF minus0679 minus0557 278 minus0652 minus0209 25118Mn minus0758 minus0557 295 minus0704 minus0511 31618Mn5Cr minus0608 minus0288 162 minus0577 minus0345 134

10 20 30 40 50 60 70 80 90

Inte

nsity

2θ

REF

SS

LorSS LL HG S

ZnO

L

(a)

10 20 30 40 50 60 70 80 90

Inte

nsity

2θ

18Mn

L L SGLG

HorG SSSS LL HG SL

ZnO

(b)

10 20 30 40 50 60 70 80 90

HH

Inte

nsity

2θ

18Mn5Cr

L L L GLG

HorG S SSSS S LL G

ZnO

(c)

Figure 3 XRD patterns of the nonadherent rust (NAR) formed on (a) REF (b) 18Mn and (c) 18Mn5Cr for 56 days in 35 NaCl solution at60degC where G L S and H represent goethite lepidocrocite magnetite (or maghemite) and hematite respectively


other hand the electrochemical reduction of rust formed on18Mn5Cr for 56-day period was not involved in the potentialrange between the corrosion potential and the potential by100mV lower than the corrosion potential It decreased boththe corrosion rate and the Tafel slope in Table 4 as a typicalcathodic behavior of steel with a protective rust layerMeanwhile the electrochemical reduction of rust formed on18Mn for 56-day period was involved in the entire range ofpotential between the corrosion potential and the potentialby 100mV lower than the corrosion potential It increasedthe cathodic current in Figure 2(b) pretending to increasethe corrosion rate in Table 4 unlike in Figure 1 e elec-trochemical reduction of rust formed on REF for 56-dayperiod was involved near a potential by 100mV lower thanthe corrosion potential increasing the Tafel slope with thedecreased corrosion rate in Table 4 though the cathodiccurrent increased in Figure 2(b) Hence the extrapolationmethod could not provide reliable data for the instantaneouscorrosion rate of steels with various alloying elements andimmersion periods

33 Analysis of Nonadherent Rust by XRD and RamanSpectroscopy Figure 3 shows the XRD spectra of the NARsfrom the alloys immersed for 56 days e NARs consisted ofgoethite (JCPDS no 29-0713) lepidocrocite (JCPDS no 44-1415) spinel oxide (magnetite (JCPDS no 39-1346) ormaghemite (JCPDS 19-0629)) and hematite (JCPDS no 33-0664) e NAR constituents were independent of alloyingelements Table 5 shows the quantitative analysis summaries ofthe NARs e concentration of each iron oxide in the NARsdepended on the alloying element Compared with no alloyingelement the addition of chromium as an alloying elementincreased the concentration of goethite which is beneficial tothe corrosion resistance of steels [15ndash18] but decreased theconcentrations of hematite as well as spinel oxide whichnegatively affects the corrosion resistance of steels [15ndash18] eaddition of manganese as an alloying element also slightlyincreased the concentrations of goethite but not asmuch as thatby chromium ese results are consistent with the effects ofalloying elements on corrosion resistance described in Section31 and 32 Additionally the total concentration of iron oxidesin Table 5 was far from 100 is difference was caused byeither the large amounts of amorphous rust presented duringthe initial period [28 44ndash46] or detection limits of XRD andRaman spectroscopy on fine grains [44ndash46]

Figure 4 shows the Raman spectra of the NARs formedon the alloys e Raman spectra of the NARs sampled fromREF demonstrate the presence of goethite lepidocrocite

hematite and magnetite which was confirmed by the ab-sence of the broadband at 710 cmminus1 [47] e Raman spectraof the NAR formed on the 18Mn mainly presented bands at554 390 621 598 and 500 cmminus1 where the first two bandscorrespond to goethite and the last three bands possiblycorrespond to Mn-rich bixbyite ((MnFe)2O3) [48] In ad-dition to major bands bands for magnetite and hematitewere detected with low intensity in the Raman spectra elow density of hematite is due to the fact that manganesepromotes the formation of Mn-rich iron bixbyite instead ofthe formation of hematite in NARs In addition no detectionof lepidocrocite in the Raman spectrum from the 18Mn ispossible due to low sensitivity of lepidocrocite in Ramanspectroscopy which was also observed in the NARs sampledfrom REF in Figure 4 corresponding to 108 of lep-idocrocite as listed in Table 5 e Raman spectrum of theNARs formed on the 18Mn5Cr was also similar to that fromthe NARs of the 18Mn with an exception of the absence ofbands from Mn-rich bixbyite e absence of Mn-rich ironoxide in the NARs from the 18Mn5Cr is due to the stabi-lization of oxyhydroxides by chromium as listed in Table 5

XRDandRaman spectrum analysis did not findmaghemiteand akaganeite in the NARs in comparison to past experiments

Table 5 Results on XRD qualitative analysis of nonadherent rusts (NARs) formed for 56-day exposure in 35 NaCl solution according tothe internal standard method

AlloysPhase fraction (wt)

Goethite Akaganeite Lepidocrocite Spinel oxidelowast Hematite TotalREF 02 00 108 47 74 21118Mn 10 00 99 53 40 20218Mn5Cr 42 00 103 03 46 194lowastMagnetite or maghemite

1000 800 600 400 200

0

50

100

150

200

250

300

L

S

G

H

S

GG

LH

H

Rela

tive i

nten

sity

Wave number

HS

API 18Mn 18Mn5Cr

G

Figure 4 Raman spectra of the nonadherent rust (NAR) formedon REF 18Mn and 18Mn5Cr for 56 days in 35 NaCl solution at60degC where G L S and H represent goethite lepidocrocitemagnetite (or maghemite) and hematite respectively S spineloxide H α-Fe2O3 G α-FeOOH L γ-FeOOH


and previous studies that were performed at room temperature[18 49]e formation of hematite or Mn-rich iron oxide fromdihydroxylation of oxyhydroxide via maghemite [22] may haveresulted from conducting the experiment at a higher tem-perature than at room temperature increasing the rate of thereaction for formation of hematite e higher testing tem-perature may also have caused transformation of akaganeite tostable oxyhydroxide or hematite [29]

erefore the NARs from all the alloys independent ofalloying elements consisted of goethite lepidocrocitemagnetite and hematite However the concentration ofconstituents in the NARs depended on alloying elementsashyecting corrosion resistance of the alloys

34 Analysis of Adherent Rust by XRD and TEM Figure 5shows the spectra of rusts sampled from the alloys immersedfor 56 days Two measurement methods for the XRDspectrum both demonstrate the presence of spinel oxide inthe ARs despite the dishyerence in their intensities After-wards the spinel oxide was identied with magnetite fromthe results of EELS analysis as shown in Table 6 and (3)

For more detailed examination the ARs were used forTEM analysis with EDS SAED and EELS eir results areshown in Figures 6ndash8 Figure 6(a) shows that the ARssampled from the REF consisted of white and gray regionsBoth regions contained iron and oxygen but the whiteregion had lower concentration of iron than the gray regionas shown in Figure 6(b) In addition the EELS analysis asshown in Table 6 and Figure 9 demonstrated higher con-centration of ferric iron in the white region which formedalong the alloyrust interface and across the AR in a lineform such as a grain boundary To satisfy the EDS and EELSanalysis results the oxidation state of iron is higher and theatomic ratio of iron to oxygen is lower in the white regione Pt peak observed from EDS analysis came from plati-num coated on the sample surface before FIB cutting e Ptpeak was no more mentioned hereafter e SAED analysisfurther supports the ndings where the white region nearthe metalrust interface mainly consists of feroxyhyte(JCPDS no 18-0087) and magnetite as shown in Figure 6(c)while the gray region is identied with magnetite as shownin Figure 6(d) Hence the distribution of the oxidation stateof iron in the ARs from the REF indicates that the pene-tration of oxygen through a fast transport pathway controlsthe corrosion process of the REF

Figures 7(a) and 7(b) provide TEM images of the ARs onthe 18Mn and the EDS analyses respectively Contrast in therust as shown in Figure 7(a) is relatively constant comparedto that in Figure 6(a) and the concentration of ironmanganese and oxygen remained constant as in the REFexcept for the presence of metallic components shown aspoint 2 in Figure 7(a) e latter is near the ARNAR in-terface In addition the ratio shown in Table 6 and Figure 9 isalmost constant regardless of the area and was lower thanthe ratio detected from the ARs from the REFis outcomeindicates that the oxidation state of iron in the ARs from the18Mn is lower than that in the ARs from the REF [41] elower oxidation state of iron in the ARs was conrmed by the

2θ

Normal

SS SS

(202)Fe(101)Fe

S

SS

SSS

(202)Fe(200)Fe(101)Fe

Thin

(200)Fe

REF

10 20 30 40 50 60 70 80 90

(a)

S SSS

(200)Fe

S

(101)Fe

SS

SSS

(311)Fe(220)Fe(101)Fe

NormalThin

(200)Fe

18Mn

10 20 30 40 50 60 70 80 902θ

(b)

(220)Fe

S SS

(200)Fe

S

(101)Fe (200)Fe

S

SSS

(311)Fe(220)Fe(101)Fe

NormalThin

18Mn5Cr

10 20 30 40 50 60 70 80 902θ

(c)

Figure 5 XRD patterns of the adherent rust (AR) formedon (a) REF (b) 18Mn and (c) 18Mn5Cr for 56 days in 35NaCl solution at 60degC where S represents magnetite (ormaghemite)


identification of the ARs as magnetite from SAED analysis asshown in Figure 7(d) Furthermore more TEM spots with aninterplanar spacing of hkl (dhkl) in Figure 7(d) than inFigure 6(c) or 6d indicate that the AR grain sizes on the

18Mn is smaller than those on the REF when the aperturesizes marked as the dot circles as shown are compared inFigures 6(a) and 7(a) From the abovementioned resultsmanganese as an alloying element aided the uniform

Table 6 Summary on the integral intensity ratio of Fe L3 edge peak to Fe L2 edge peak depending on various positions among rust formed onREF 18Mn and 18Mn5Cr for 56 days in 35 NaCl solution at 60oC

Alloy Distance from metalrust interface (μm) Points in Figures 6ndash8 I(Fe L3)I(Fe L2)

REF

0133 e1 in Figure 6(a) 6010333 e2 in Figure 6(a) 5500320 e3 in Figure 6(a) 6260400 e4 in Figure 6(a) 6820827 e5 in Figure 6(a) 5970880 e6 in Figure 6(a) 7061100 e7 in Figure 6(a) 637

18Mn0165 e1 in Figure 7(a) 5650235 e2 in Figure 7(a) 5460424 e3 in Figure 7(a) 557

18Mn5Cr0036 e1 in Figure 8(a) 4650100 e2 in Figure 8(a) 5460229 e3 in Figure 8(a) 536

e1

(b)

e2

e3

e4

e5

e6e7

2 1

200 (nm)

(a)

00 04 08 12

0

20

40

60

80

100

Pt

FeMn

OPt

Inte

nsity

Distance (μm)

Matrix

(b)

(110)δ or (440)M

(100)δ or (311)M

(102)δ or (511)M(002)δ

51 (nm)

(c)

(633)M(710)M(622)M(620)M(440)M

51 (nm)

(110)M(102)M(002)M (100)M(100)M

(d)

Figure 6 Cross-sectional TEM image (a) EDS line profile (b) and SAEDs (c-d) of regions 1 and 2 in rust formed during 56-day immersionof REF in 35 NaCl solution at 60oC where the subscripts δ and M indicate feroxyhyte and magnetite respectively


formation of rust and the refinement of the grain sizes ofARs allowing oxygen to penetrate into ARs retarding theformation of ferric ion and ultimately increasing the cor-rosion resistance of the 18Mn

Figure 8(a) shows a TEM image of the ARs from the18Mn5Cr Similar to Figure 7(a) the image was almostconstant contrast whereas the EDS intensities in Figure 8(b)were almost constant unlike in Figure 7(b) except the de-creased intensity of iron from a distance longer than 02μmaway from the alloyAR interface As shown in Figure 8(c)those outcomes caused the enrichment of manganese andchromium Despite the enrichment of chromium and man-ganese however the ratio shown in Table 6 and Figure 9 isalmost as constant as that of AR formed on the 18Mn in-dicating that the oxidation state of iron in the AR fromthe 18Cr5Mn is the same as that of the AR from the 18MnFigures 8(d) and 8(e) demonstrate that the ARs from the18Cr5Mn were mainly magnetite and have the finestgrain based on the comparison of aperture sizes in Figures6(a) 7(a) and 8(a) Here chromium and manganese en-richments near the ARNAR interface may be explainedwith the substitution of ferric ion and ferrous ion by chro-mium(III) and manganese(II) in magnetite respectively

As both chromium and manganese retard the formation ofmagnetite [34] and aid the formation of oxyhydroxide in theNARs iron ions may have diffused out and promoted theenrichment erefore chromium aids the uniform rustformation and the refinement of the grain size in ARs and theformation of enriched (Cr Mn) oxyhydroxide in the NARshindering effective oxygen penetration into ARs and in-creasing the corrosion resistance of 18Mn5Cr

4 Discussion

Since the corrosion resistance of steels was controlled by thepenetration of oxygen into rust the following modificationof rust properties by chromium and manganese improvedthe corrosion resistance as sketched in Figure 10 Comparedto the rust on the REF both chromium and manganeseaccelerate the formation of goethite in NARs and fine-grained magnetite in ARs though the chromium is moreeffective than manganese as shown in Figures 10(b) and 10(c) e higher effectiveness of chromium on corrosionresistance of steels is because both the formation rate andrefinement of goethite are enhanced in NARs [4 36 50] aswell as AR grain sizes are more refined [36] e higher

5

123

4e3

e2

e1

(b)

02 (μm)

(a)

00 02 04 06 08

0

20

40

60

80

100

Pt

FeMn

OPt

Inte

nsity

Distance (μm)

Matrix

(b)

Positionin (a)

Chemical composition (wt)Fe Mn O668760762716

134184463343

19856

192250

12

43

(c)

51 (nm)(311)M

(220)M

(400)M

(422)M

(511)M

(440)M

(533)M

(731)M

(751)M

(d)

Figure 7 Cross-sectional TEM image (a) EDS line profile (b) EDS quantitative analysis of selected points 1 2 3 and 4 (c) and SAED (d) ofregion 5 in rust formed during 56-day immersion of 18Mn in 35 NaCl solution at 60degC where subscript M indicates magnetite


effectiveness of chromium on the formation of goethite hasbeen explained with both facilitated incorporation ofchromium into goethite as chromium is more soluble thanmanganese [51 52] and faster precipitation of chromium(III) ion to Cr(OH)3 than ferrous ion during the oxidation ofthe ferrous solutions [50] e fast pathway where oxygen istransported across NARs is provided by pores or theirsurface area e porosity of rust is affected by phasetransformation of rust interparticle spacing type of ironoxide and substituting ions into the oxide grain size andcrystal structure [24] However a higher porosity does notalways result in a higher transport rate due to mobility andthe size of the pore [24] For example more refined grainprovides a low transport rate of oxygen despite its highsurface area Accordingly the study on mobility as well asthe size of the pore remains for future work erefore thelower transport rate of oxygen across rust on the alloy steels

(18Mn 18Mn5Cr) was explained with the more refined grainsize of goethite in the NARs without further mentioningporosity

Unlike previous studies [15 16 18] which state thatmagnetite is related to a decrease in corrosion resistance ofsteel the ARs formed on the alloy steels with higher cor-rosion resistances contained fine magnetite as a maincomponent e discrepancy is due to the difference in thelocation of rust from the alloyrust interface Magnetite isformed from the following reactions slow oxidation offerrous hydroxide by way of GR incorporation of ferrousion into oxyhydroxide [7] or dissolution-precipitationprocessmdashthe early precipitated oxyhydroxide reacts withthe dissolved ferrous hydroxide to produce magnetite[29 53] On the alloy steels magnetite exists as a main oxidein the inner layer of ARs because of the difficulty intransporting oxygen through both NARs and ARs However

1

34

e1

e2

e3

52

100 (nm)

(a)

00

0

20

40

60

80

100

Pt

FeMnCr

OPt

Inte

nsity

Distance (microm)

Matrix

01 02 03 04

(b)

Positionin (a)

Chemical composition (wt )Fe Mn Cr O

739

506 12883

186 531158

22254308

631321

(c)

(440)M

(400)M(311)M

51 (nm)

(d)

(440)M

(400)M

(311)M

51 (nm)

(e)

Figure 8 Cross-sectional TEM image (a) EDS line profile (b) EDS quantitative analysis of selected points 1 2 and 3 (c) and SAEDs(d-e) of regions 4 and 5 in rust formed during 56-day immersion of 18Mn5Cr in 35 NaCl solution at 60degC where subscript Mindicates magnetite


00 02 04 06 0845

50

55

60

65

70

75

REF 18Mn 18Mn5Cr

I(Fe

L3)

I(Fe

L2)

Distance from metalrust interface (microm)

Figure 9 Integral intensity ratio of Fe L3 edge peak to Fe L2 edge peak depending on the distance from the metallic surface of REF 18Mnand 18Mn5Cr presented in Table 6

AR layer

NAR layer

M

δ + M

REF

(a)

M

18Mn

(b)

18Mn5Cr

M

(c)

Figure 10 Schematic diagrams of rust layers formed on REF (a) 18Mn (b) and 18Mn5Cr (c) in 35 NaCl solution for 56 days at 60degCwhere solid circle M and δ indicate goethite magnetite and feroxyhyte respectively


the formation of the less-protective rust layer like the NARand the AR on the REF provides a fast pathway for oxygenpenetration and aids oxyhydroxide formation [28] de-creasing the concentration of magnetite Hence the higherconcentration of magnetite in the AR indicates the higherresistance of the alloy on which the AR is formed unlike theexpectation according to (1)

5 Conclusions

From the evaluation of corrosion resistance of REF 18Mnand 18Mn5Cr in 60degC 35NaCl solution and the analysis ofthe AR and NAR by XRD Raman spectroscopy TEM-EDSTEM-SADP and TEM-EELS the corrosion process and theeffects of chromium and manganese on the process aredescribed in detail in the following

(1) In 60degC NaCl solution the corrosion processes of allthe alloys were controlled by the oxygen transportthrough the rust layer e weight loss behaviorconformed to a typical parabolic law the oxidationstate of iron in rust was higher along the fast pathwaybut it was not proportional to the longer distancefrom the alloyAR interface

(2) Both chromium and manganese as alloying elementsnot only increased the amounts of goethite in NARsbut also refined the AR grain size In addition thealloying elements decreased the concentration ratioof ferric ion to ferrous ion in ARs indicating thedifficulty in oxygen penetration

(3) e higher corrosion resistance of 18Mn5Cr resultedfrom the effectiveness of chromium in refinementsof AR grains and increased amounts of goethitein NARs

In addition the Tafel extrapolation method does notprovide reliable data for the instantaneous corrosion rate ofsteels with various alloying elements and immersion periodsbecause the electrochemical reduction rate of rust dependson its constituents as well as corrosion potentials which areaffected by the alloying element

Conflicts of Interest

e author declares that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

e authors gratefully acknowledge the financial supportsfrom POSCO

References

[1] H N Han C-S Oh G Kim and O Kwon ldquoDesign methodfor TRIP-aided multiphase steel based on a microstructure-based modelling for transformation-induced plasticity andmechanically induced martensitic transformationrdquo Materials

Science and Engineering A vol 499 no 1-2 pp 462ndash4682009

[2] O Soderberg ldquoCorrosion behaviour of FendashMnndashSi based shapememory steels trained by cold rollingrdquo Materials Science andEngineering A vol 273ndash275 pp 543ndash548 1999

[3] M B Kannan R K S Raman and S Khoddam ldquoCom-parative studies on the corrosion properties of a FendashMnndashAlndashSisteel and an interstitial-free steelrdquo Corrosion Science vol 50no 10 pp 2879ndash2884 2008

[4] Y Hyun and H Kim ldquoEffects of alloying elements (Cr Mn)on corrosion properties of carbon steel in synthetic seawaterrdquoKorean Journal of Metals and Materials vol 54 pp 68ndash782016

[5] Y Hyun and H Kim ldquoEffects of alloying elements on thecorrosion properties of high strength steel in a sour envi-ronmentrdquo Korean Journal of Metals and Materials vol 54no 12 pp 885ndash892 2016

[6] Y S Zhang and X M Zhu ldquoElectrochemical polarization andpassive film analysis of austenitic FendashMnndashAl steels in aqueoussolutionsrdquo Corrosion Science vol 41 no 9 pp 1817ndash1833 1998

[7] X M Zhu and Y S Zhang ldquoInvestigation of the electro-chemical corrosion behavior and passive film for Fe-Mn Fe-Mn-Al and Fe-Mn-Al-Cr alloys in aqueous solutionsrdquoCorrosion Science vol 54 no 1 pp 3ndash12 1998

[8] P H Refait M Abdelmoula and J M R Genin ldquoMecha-nisms of formation and structure of green rust one in aqueouscorrosion of iron in the presence of chloride ionsrdquo CorrosionScience vol 40 no 9 pp 1547ndash1560 1998

[9] G Mcadam and D J Young ldquoMechanisms of the simulta-neous sulfidation and oxidation of Fe-Mn alloysrdquo CorrosionScience vol 38 no 2 pp 247ndash266 1996

[10] K Asami and M Kikuchi ldquoCharacterization of rust layers onweathering steels air-exposed for a long periodrdquo MaterialsTransactions vol 43 no 11 pp 2812ndash2825 2002

[11] J Rawers ldquoOxidation characteristics of Fendash18Crndash18Mn-stainless steel alloysrdquo Oxidation of Metals vol 74 no 3-4pp 167ndash178 2010

[12] D Neff P Dillmann L Bellot-Gurlet and G BerangerldquoCorrosion of iron archaeological artefacts in soil charac-terisation of the corrosion systemrdquo Corrosion Science vol 47no 2 pp 515ndash535 2005

[13] R E Melchers ldquoEffect of small compositional changes onmarine immersion corrosion of low alloy steelsrdquo CorrosionScience vol 46 no 7 pp 1669ndash1691 2004

[14] R E Melchers ldquoLong-term corrosion of cast irons and steel inmarine and atmospheric environmentsrdquo Corrosion Sciencevol 68 pp 186ndash194 2013

[15] S Hara T Kamimura H Miyuki and M YamashitaldquoTaxonomy for protective ability of rust layer using itscomposition formed on weathering steel bridgerdquo CorrosionScience vol 49 no 3 pp 1131ndash1142 2007

[16] T Kamimura S Hara H Miyuki M Yamashita andH Uchida ldquoComposition and protective ability of rust layerformed on weathering steel exposed to various environ-mentsrdquo Corrosion Science vol 48 no 9 pp 2799ndash2812 2006

[17] A L Morales D Cartagena J L Rendon and A Valencialdquoe relation between corrosion rate and corrosion productsfrom low carbon steelrdquo Physica Status Solidi (B) vol 220no 1 pp 351ndash356 2000

[18] F R Perez C A Barrero A R Hight Walker K E Garciaand K Nomura ldquoEffects of chloride concentration immer-sion time and steel composition on the spinel phase forma-tionrdquo Materials Chemistry and Physics vol 117 no 1pp 214ndash223 2009


[19] M Yamashita H Miyuki Y Matsuda H Nagano andT Misawa ldquoe long term growth of the protective rust layerformed on weathering steel by atmospheric corrosion duringa quarter of a centuryrdquo Corrosion Science vol 36 pp 283ndash299 1994

[20] P H Bauer J M Genin and D Rezel ldquoMossbauer effectevidence of chlorine environments in ferric oxyhydroxidesfrom iron corrosion in chlorinated aqueous solutionrdquo Hy-perfine Interactions vol 28 no 1-4 pp 757ndash760 1986

[21] R A Robie B S Hemingway and J R Fischer Dermo-dynamic properties of minerals and related substances at 29815K and 1 bar (105 pascals) pressure and high temperaturesWashington DC USA 1978

[22] R M Cornell and U Schwertmann De Iron Oxides p 181VCH Publishers New York NY USA 1996

[23] S J Oh D C Cook and H E Townsend ldquoAtmospheric cor-rosion of different steels in marine rural and industrial envi-ronmentsrdquo Corrosion Science vol 41 no 9 pp 1687ndash1702 1999

[24] R M Cornell and U Schwertmann De Iron Oxidespp 98ndash110 VCH Publishers New York NY USA 2006

[25] U R Evans and C A J Taylor ldquoMechanism of atmosphericrustingrdquo Corrosion Science vol 12 no 3 pp 227ndash246 1972

[26] J T Keiser C W Brown and R H Heidersbach ldquoeelectrochemical reduction of rust films on weathering steelsurfacesrdquo Journal of the Electrochemical Society vol 129no 12 pp 2686ndash2689

[27] J P Jolivet E Tronc and C R Chaneac ldquoIron oxides frommolecular clusters to solid A nice example of chemicalversatilityrdquo Comptes Rendus Geoscience vol 338 no 1-7pp 488ndash497 2006

[28] T Misawa T Kyuno W Suetaka and S Shimodaira ldquoemechanism of atmospheric rusting and the effect of Cu and Pon the rust formation of low alloy steelsrdquo Corrosion Sciencevol 11 no 1 pp 35ndash48 1971

[29] T Ishikawa Y Kondo A Yasukawa and K KandorildquoFormation of magnetite in the presence of ferric oxy-hydroxidesrdquo Corrosion Science vol 40 no 7 pp 1239ndash12511998

[30] Y Tamaura K Ito and T Katsura ldquoTransformation of γ-FeO(OH) to Fe3O4 by adsorption of iron(II) ion on γ-FeO(OH)rdquoJournal of the Chemical Society Dalton Transactions no 2pp 189ndash194 1983

[31] R M Cornell ldquoe influence of some divalent cations on thetransformation of ferrihydrite to more crystalline productsrdquoClay Minerals vol 23 no 3 pp 329ndash332 1988

[32] R M Cornell and R Giovanoli ldquoe influence of copper onthe transformation of ferrihydrite (5Fe2O3 rarr 9H2O) intocrystalline products in alkaline mediardquo Polyhedron vol 7no 5 pp 385ndash391 1988

[33] C A Barrero A L Morales J Restrepo et al ldquoSynthesis ofmagnetite in presence of Cu2+ or Cr3+rdquo Hyperfine In-teractions vol 134 no 1 pp 141ndash152 2001

[34] T Ishikawa M Kumagai A Yasukawa K KandoriT Nakagama and F Yuse ldquoInfluences of metal ions on theformation of γ-FeOOH and magnetite rustsrdquo CorrosionScience vol 44 no 5 pp 1073ndash1086 2002

[35] C A Barrero A L Morales J Mazo-Zuluaga et alldquoSynthesis and Mossbauer characterization of Cu and Crdoped magnetitesrdquo Revista de Metalurgia (Madrid) vol 39pp 62ndash67 2003

[36] A L Morales C A Barrero F Jaramillo C Arroyave andJ M Greneche ldquoProperties of goethite grown under thepresence of Cr3+ Cu2+ and Mn2+ ionsrdquo Hyperfine Inter-actions vol 148149 no 1ndash4 pp 135ndash144 2003

[37] D W Kim and H Kim ldquoEffects of alloying elements oncorrosion resistance of low alloyed steels in a seawater ballasttank environmentrdquo Korean Journal of Metals and Materialsvol 48 no 6 pp 523ndash532 2010

[38] ASTM G 1 Standard Practice for Preparing Cleaning andEvaluating Corrosion Test Specimens ASTM InternationalWest Conshohocken PA USA 2003

[39] D A Jones Principle and Prevention of Corrosion Prentice-Hall New Jersey NY USA 2nd edition 1996

[40] C Suryanarayana and M G Norton X-ray DiffractionndashAPractical Approach Premium Publishing Co New York NYUSA 1998

[41] P A van Aken B Liebscher and V J Styrsa ldquoQuantitativedetermination of iron oxidation states in minerals usingFe L 23-edge electron energy-loss near-edge structure spec-troscopyrdquo Physics and Chemistry of Minerals vol 25 no 5pp 323ndash327 1998

[42] A Raman A Razvan B Kuban K A Clement andW E Graves ldquoCharacteristics of the rust from weathering steelsin Louisiana bridge spansrdquo Corrosion vol 42 pp 447ndash455 1986

[43] Y Zou J Wang and Y Y Zheng ldquoElectrochemical techniquesfor determining corrosion rate of rusted steel in seawaterrdquoCorrosion Science vol 53 no 1 pp 208ndash216 2011

[44] M Yamashita H Miyuki H Nagano and T MisawaldquoStabilizing process of rust layer formed on weathering steelsby atmospheric corrosion for a long periodrdquo Zairyo-to-Kankyo vol 43 no 1 pp 26ndash32 1994

[45] M Yamashita H Nagano T Misawa and H E TownsendldquoStructure of protective rust layers formed on weatheringsteels by long-term exposure in the industrial atmospheres ofJapan and North Americardquo ISIJ International vol 38 no 3pp 285ndash290 1998

[46] M Yamashita and T Misawa ldquoRecent progress in the study ofprotective rust-layer formation on weathering steelrdquo inProceedings of NACE 53rd Annual Conference (Corrosion 98)San Diego CA USA March 1998

[47] S J Oh D C Cook and T E Townsend ldquoCharacterization ofiron oxides commonly formed as corrosion products onsteelrdquo Hyperfine Interactions vol 112 pp 59ndash65 1998

[48] F Ospitali D C Smith and M Lorblanchet ldquoPreliminaryinvestigations by Ramanmicroscopy of prehistoric pigments inthe wall-painted cave at Roucadour Quercy Francerdquo Journal ofRaman Spectroscopy vol 37 no 10 pp 1063ndash1071 2006

[49] L Hao S Zhang J Dong and W Ke ldquoEvolution of atmo-spheric corrosion of MnCuP weathering steel in a simulatedcoastal-industrial atmosphererdquo Corrosion Science vol 59pp 270ndash276 2012

[50] M Y amashita H Uchida and D C Cook ldquoEffect of Cr3+

and SO42minus on the structure of rust layer formed on steels by

atmospheric corrosionrdquo in Outdoor Atmospheric CorrosionH Townsend Ed p 149 West Conshohocken PA USAASTM International 2002

[51] D C Cook S J Oh R Balasubramanian and M Yamashitaldquoe role of goethite in the formation of the protectivecorrosion layer on steelsrdquo Hyperfine Interactions vol 122pp 59ndash70 1999

[52] A Manceau M L Schlegel M Musso et al ldquoCrystalchemistry of trace elements in natural and synthetic goethiterdquoGeochimica et Cosmochimica Acta vol 64 no 21 pp 3643ndash3661 2000

[53] Y Tamaura and P V Buduan ldquoStudies on the oxidation of iron(II) ion during the formation of Fe3O4and α-FeO(OH) by airoxidation of Fe[OH]2 suspensionsrdquo Journal of the ChemicalSociety Dalton Transactions no 9 pp 1807ndash1811 1981


CorrosionInternational Journal of

Hindawiwwwhindawicom Volume 2018

Advances in

Materials Science and EngineeringHindawiwwwhindawicom Volume 2018


Journal of

Chemistry

Analytical ChemistryInternational Journal of


ScienticaHindawiwwwhindawicom Volume 2018

Polymer ScienceInternational Journal of



Advances in Condensed Matter Physics


International Journal of

BiomaterialsHindawiwwwhindawicom

Journal ofEngineeringVolume 2018

Applied ChemistryJournal of


NanotechnologyHindawiwwwhindawicom Volume 2018

Journal of


High Energy PhysicsAdvances in

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

TribologyAdvances in



ChemistryAdvances in


Advances inPhysical Chemistry


BioMed Research InternationalMaterials

Journal of


Na

nom

ate

ria

ls


Journal ofNanomaterials

Submit your manuscripts atwwwhindawicom

In general the transport of oxygen through rust dependson its grain size crystal structure chemical stability andporosity [19ndash24] which explains the dependency of corrosionresistance on iron oxide or oxyhydroxide According to theMelchers model during the initial state of the first stage steelsare oxidized to produce various forms of dissolved ferrous ion orprecipitated ferrous hydroxidee various forms of ferrous ionare chemically or electrochemically oxidized by oxygen toproduce different types of ferric oxyhydroxide maghemite orhematite With the elapsed time the thickened rust layer im-pedes the transport of oxygen to the steel surface During thisperiod various forms of ferric oxyhydroxide may reduce tomagnetite [25 26] incorporation of ferrous ion into ferricoxyhydroxide [27] slow oxidation of ferrous hydroxide via greenrust (GR) [28] or reaction of the dissolved ferric oxyhydroxidewith dissolved ferrous hydroxide [29 30] e first processoccurs in rust and the other processes occur at the rustsolutioninterface or at rust near the solution As an alloying elementmanganese not only impedes the formation ofmagnetite [31 32]but also encourages the formation of refined goethite Chro-mium hinders magnetitersquos nucleation [33] and growth [34]while it promotes the nucleation [33] and growth [35] of goethiteand refinement of grain [36] Both manganese and chromiumimprove corrosion resistance of steel however chromium hasa greater effect than manganese [36]

e effects of manganese and chromium on corrosionresistance [37] of high manganese steels were studied byexamining rust properties with X-ray diffraction (XRD)Raman spectroscopy energy dispersive spectroscopy (EDS)[4 5] and electron energy loss spectroscopy (EELS) adjunctto transmission electron microscopy (TEM)

2 Experimental Procedure

21 Preparation of Specimen e ingots (API60 18Mn and18Mn5Cr) with chemical compositions listed in Table 1were cast to examine the effects of corrosion resistanceof carbon steel on manganese and chromium API60 wasused as a reference material and hereafter named ldquoREFrdquo25 kg ingots were heat treated at 1150degC for 15 hoursunder an argon atmosphere and hot rolled to 45mm Bothsurfaces of the plate were mill-machined to 3mm thick-ness in order to remove the scale formed during theheat treatment en the 3mm thick plates were cut into2 cm times 1 cm times 04 cm coupons for an immersion test and1 cm times 1 cm times 04 cm coupons for a polarization test re-spectively All the surfaces were wet grounded with suc-cessive grade silicon carbide papers from 200 to 600 gritdegreased with acetone rinsed with ethanol blow-driedand finally kept in a desiccator

22 Evaluation of Corrosion Resistance e weight loss testand polarization test were conducted to evaluate corrosionresistance of the experimental alloys e tests were carried in35 NaCl aqueous solution at a constant temperature of60degC During the immersion test the coupons were supportedon cradlesmdasha glass cradle with protrusionsmdashto minimize thecradle-couple contact area In each capped vessel eachcoupon was immersed in 200mL of 35 NaCl solutionImmersion periods were 1 7 14 28 and 56 days for REF18Mn and 18Mn5Cr respectively On every 7th day thesolution was replaced with a fresh solution tomaintain the pHof the solution within 02 For the weight loss measurementsthe rust formed on the coupon was removed and the exposedcoupon was immersed in a hydrochloric acid inhibited withhexamethylenetetramine (0025M C6H12N4+ 543M HCl) atroom temperature in an ultrasonic bath for 5ndash10 minutesaccording to ASTMG1 [38] e weight measurement resultswere used to calculate the weight at an immersion time andmean weight loss rate as shown in

Mean weight loss rate ti( 1113857 ΔW ti( 1113857minusΔW timinus1( 1113857

ti minus timinus1 (2)

where ΔW(ti) is the weight loss per surficial area at im-mersion time ti

e immersion test was repeated twice under the samecondition for reproducibility If the results showed highdeviations the immersion test was repeated untilcrediblereliable data were obtained

e cathodic polarization test was conducted to measureinstantaneous corrosion rates (icorr) [39] and the anodicpolarization test was performed to observe corrosion be-haviors To prepare a working electrode the square couponswere embedded in epoxy resin [37] with an exposure area of1 cm2 wet grounded with 600 grit silicon carbide papersrinsed with ethanol dried and stored in a desiccator Asaturated calomel electrode (SCE) and a platinummesh wereused as a reference electrode and a counter electrode re-spectively e mounted coupons from 1-day and 56-dayimmersion in the chloride solution were anodically or ca-thodically polarized by a corrosion potential at the scan rateof 20mVmin By linearly fitting the polarization curvesaround the potentials by 100mV lower than corrosionpotentials cathodic Tafel slopes (βc) were obtained as well asinstantaneous corrosion rates

23 Analysis of Rust At the end of 56-day immersion thecoupons with their vessels were placed in the ultrasonic bathfor 15ndash20 seconds to remove nonadherent rusts (NARs) andthen the coupons were extracted e NARs were filtrated

Table 1 Chemical composition of the experimental alloys

Name Phase(s)Chemical composition ( wt)

C Mn Cr Ni FeREF(API60) α+ bainite 0067 16 002 02 Balance18Mn c 06 184 lt0005 lt0005 Balance18Mn5Cr c 06 185 51 lt0005 Balance








I of Fe L2 (3)


3 Results












0 10 20 30 40 50 60

000

001

002W

eigh

t los

s (gc

mminus2

)


REF18Mn18Mn5Cr

(a)

0 10 20 30 40 50 6000

20 times 10minus4

40 times 10minus4

60 times 10minus4

80 times 10minus4

10 times 10minus3

12 times 10minus3

14 times 10minus3

16 times 10minus3

18 times 10minus3

Mea

n w

eigh

t los

s rat

e (gc

mminus2

dminus1 )


REF18Mn18Mn5Cr

(b)


10

times 10

minus7

10

times 10

minus6

10

times 10

minus5

10

times 10

minus4

10

times 10

minus3

10

times 10

minus2

10

times 10

minus1

minus080

ndash060

minus040

ndash020

000

020

040

Pote

ntia

l V

SCE




(a)

REF-56d18Mn-1d


10 times

10minus

7

10 times

10minus

6

10 times

10minus

5

10 times

10minus

4

10 times

10minus

3

ndash110

ndash100

ndash090

ndash080

ndash070

ndash060

minus050

Pote

ntia

l V

SCE


REF-1d

(b)










10 20 30 40 50 60 70 80 90

Inte

nsity

2θ

REF

SS

LorSS LL HG S

ZnO

L

(a)

10 20 30 40 50 60 70 80 90

Inte

nsity

2θ

18Mn

L L SGLG

HorG SSSS LL HG SL

ZnO

(b)

10 20 30 40 50 60 70 80 90

HH

Inte

nsity

2θ

18Mn5Cr

L L L GLG

HorG S SSSS S LL G

ZnO

(c)











1000 800 600 400 200

0

50

100

150

200

250

300

L

S

G

H

S

GG

LH

H

Rela

tive i

nten

sity

Wave number

HS

API 18Mn 18Mn5Cr

G








2θ

Normal

SS SS

(202)Fe(101)Fe

S

SS

SSS

(202)Fe(200)Fe(101)Fe

Thin

(200)Fe

REF

10 20 30 40 50 60 70 80 90

(a)

S SSS

(200)Fe

S

(101)Fe

SS

SSS

(311)Fe(220)Fe(101)Fe

NormalThin

(200)Fe

18Mn

10 20 30 40 50 60 70 80 902θ

(b)

(220)Fe

S SS

(200)Fe

S

(101)Fe (200)Fe

S

SSS

(311)Fe(220)Fe(101)Fe

NormalThin

18Mn5Cr

10 20 30 40 50 60 70 80 902θ

(c)







REF




e1

(b)

e2

e3

e4

e5

e6e7

2 1

200 (nm)

(a)

00 04 08 12

0

20

40

60

80

100

Pt

FeMn

OPt

Inte

nsity

Distance (μm)

Matrix

(b)

(110)δ or (440)M

(100)δ or (311)M

(102)δ or (511)M(002)δ

51 (nm)

(c)

(633)M(710)M(622)M(620)M(440)M

51 (nm)

(110)M(102)M(002)M (100)M(100)M

(d)






4 Discussion


5

123

4e3

e2

e1

(b)

02 (μm)

(a)

00 02 04 06 08

0

20

40

60

80

100

Pt

FeMn

OPt

Inte

nsity

Distance (μm)

Matrix

(b)

Positionin (a)


134184463343

19856

192250

12

43

(c)

51 (nm)(311)M

(220)M

(400)M

(422)M

(511)M

(440)M

(533)M

(731)M

(751)M

(d)






1

34

e1

e2

e3

52

100 (nm)

(a)

00

0

20

40

60

80

100

Pt

FeMnCr

OPt

Inte

nsity

Distance (microm)

Matrix

01 02 03 04

(b)

Positionin (a)


739

506 12883

186 531158

22254308

631321

(c)

(440)M

(400)M(311)M

51 (nm)

(d)

(440)M

(400)M

(311)M

51 (nm)

(e)



00 02 04 06 0845

50

55

60

65

70

75

REF 18Mn 18Mn5Cr

I(Fe

L3)

I(Fe

L2)



AR layer

NAR layer

M

δ + M

REF

(a)

M

18Mn

(b)

18Mn5Cr

M

(c)




5 Conclusions








Acknowledgments


References





























































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls










I of Fe L2 (3)


3 Results












0 10 20 30 40 50 60

000

001

002W

eigh

t los

s (gc

mminus2

)


REF18Mn18Mn5Cr

(a)

0 10 20 30 40 50 6000

20 times 10minus4

40 times 10minus4

60 times 10minus4

80 times 10minus4

10 times 10minus3

12 times 10minus3

14 times 10minus3

16 times 10minus3

18 times 10minus3

Mea

n w

eigh

t los

s rat

e (gc

mminus2

dminus1 )


REF18Mn18Mn5Cr

(b)


10

times 10

minus7

10

times 10

minus6

10

times 10

minus5

10

times 10

minus4

10

times 10

minus3

10

times 10

minus2

10

times 10

minus1

minus080

ndash060

minus040

ndash020

000

020

040

Pote

ntia

l V

SCE




(a)

REF-56d18Mn-1d


10 times

10minus

7

10 times

10minus

6

10 times

10minus

5

10 times

10minus

4

10 times

10minus

3

ndash110

ndash100

ndash090

ndash080

ndash070

ndash060

minus050

Pote

ntia

l V

SCE


REF-1d

(b)










10 20 30 40 50 60 70 80 90

Inte

nsity

2θ

REF

SS

LorSS LL HG S

ZnO

L

(a)

10 20 30 40 50 60 70 80 90

Inte

nsity

2θ

18Mn

L L SGLG

HorG SSSS LL HG SL

ZnO

(b)

10 20 30 40 50 60 70 80 90

HH

Inte

nsity

2θ

18Mn5Cr

L L L GLG

HorG S SSSS S LL G

ZnO

(c)











1000 800 600 400 200

0

50

100

150

200

250

300

L

S

G

H

S

GG

LH

H

Rela

tive i

nten

sity

Wave number

HS

API 18Mn 18Mn5Cr

G








2θ

Normal

SS SS

(202)Fe(101)Fe

S

SS

SSS

(202)Fe(200)Fe(101)Fe

Thin

(200)Fe

REF

10 20 30 40 50 60 70 80 90

(a)

S SSS

(200)Fe

S

(101)Fe

SS

SSS

(311)Fe(220)Fe(101)Fe

NormalThin

(200)Fe

18Mn

10 20 30 40 50 60 70 80 902θ

(b)

(220)Fe

S SS

(200)Fe

S

(101)Fe (200)Fe

S

SSS

(311)Fe(220)Fe(101)Fe

NormalThin

18Mn5Cr

10 20 30 40 50 60 70 80 902θ

(c)







REF




e1

(b)

e2

e3

e4

e5

e6e7

2 1

200 (nm)

(a)

00 04 08 12

0

20

40

60

80

100

Pt

FeMn

OPt

Inte

nsity

Distance (μm)

Matrix

(b)

(110)δ or (440)M

(100)δ or (311)M

(102)δ or (511)M(002)δ

51 (nm)

(c)

(633)M(710)M(622)M(620)M(440)M

51 (nm)

(110)M(102)M(002)M (100)M(100)M

(d)






4 Discussion


5

123

4e3

e2

e1

(b)

02 (μm)

(a)

00 02 04 06 08

0

20

40

60

80

100

Pt

FeMn

OPt

Inte

nsity

Distance (μm)

Matrix

(b)

Positionin (a)


134184463343

19856

192250

12

43

(c)

51 (nm)(311)M

(220)M

(400)M

(422)M

(511)M

(440)M

(533)M

(731)M

(751)M

(d)






1

34

e1

e2

e3

52

100 (nm)

(a)

00

0

20

40

60

80

100

Pt

FeMnCr

OPt

Inte

nsity

Distance (microm)

Matrix

01 02 03 04

(b)

Positionin (a)


739

506 12883

186 531158

22254308

631321

(c)

(440)M

(400)M(311)M

51 (nm)

(d)

(440)M

(400)M

(311)M

51 (nm)

(e)



00 02 04 06 0845

50

55

60

65

70

75

REF 18Mn 18Mn5Cr

I(Fe

L3)

I(Fe

L2)



AR layer

NAR layer

M

δ + M

REF

(a)

M

18Mn

(b)

18Mn5Cr

M

(c)




5 Conclusions








Acknowledgments


References





























































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls







0 10 20 30 40 50 60

000

001

002W

eigh

t los

s (gc

mminus2

)


REF18Mn18Mn5Cr

(a)

0 10 20 30 40 50 6000

20 times 10minus4

40 times 10minus4

60 times 10minus4

80 times 10minus4

10 times 10minus3

12 times 10minus3

14 times 10minus3

16 times 10minus3

18 times 10minus3

Mea

n w

eigh

t los

s rat

e (gc

mminus2

dminus1 )


REF18Mn18Mn5Cr

(b)


10

times 10

minus7

10

times 10

minus6

10

times 10

minus5

10

times 10

minus4

10

times 10

minus3

10

times 10

minus2

10

times 10

minus1

minus080

ndash060

minus040

ndash020

000

020

040

Pote

ntia

l V

SCE




(a)

REF-56d18Mn-1d


10 times

10minus

7

10 times

10minus

6

10 times

10minus

5

10 times

10minus

4

10 times

10minus

3

ndash110

ndash100

ndash090

ndash080

ndash070

ndash060

minus050

Pote

ntia

l V

SCE


REF-1d

(b)










10 20 30 40 50 60 70 80 90

Inte

nsity

2θ

REF

SS

LorSS LL HG S

ZnO

L

(a)

10 20 30 40 50 60 70 80 90

Inte

nsity

2θ

18Mn

L L SGLG

HorG SSSS LL HG SL

ZnO

(b)

10 20 30 40 50 60 70 80 90

HH

Inte

nsity

2θ

18Mn5Cr

L L L GLG

HorG S SSSS S LL G

ZnO

(c)











1000 800 600 400 200

0

50

100

150

200

250

300

L

S

G

H

S

GG

LH

H

Rela

tive i

nten

sity

Wave number

HS

API 18Mn 18Mn5Cr

G








2θ

Normal

SS SS

(202)Fe(101)Fe

S

SS

SSS

(202)Fe(200)Fe(101)Fe

Thin

(200)Fe

REF

10 20 30 40 50 60 70 80 90

(a)

S SSS

(200)Fe

S

(101)Fe

SS

SSS

(311)Fe(220)Fe(101)Fe

NormalThin

(200)Fe

18Mn

10 20 30 40 50 60 70 80 902θ

(b)

(220)Fe

S SS

(200)Fe

S

(101)Fe (200)Fe

S

SSS

(311)Fe(220)Fe(101)Fe

NormalThin

18Mn5Cr

10 20 30 40 50 60 70 80 902θ

(c)







REF




e1

(b)

e2

e3

e4

e5

e6e7

2 1

200 (nm)

(a)

00 04 08 12

0

20

40

60

80

100

Pt

FeMn

OPt

Inte

nsity

Distance (μm)

Matrix

(b)

(110)δ or (440)M

(100)δ or (311)M

(102)δ or (511)M(002)δ

51 (nm)

(c)

(633)M(710)M(622)M(620)M(440)M

51 (nm)

(110)M(102)M(002)M (100)M(100)M

(d)






4 Discussion


5

123

4e3

e2

e1

(b)

02 (μm)

(a)

00 02 04 06 08

0

20

40

60

80

100

Pt

FeMn

OPt

Inte

nsity

Distance (μm)

Matrix

(b)

Positionin (a)


134184463343

19856

192250

12

43

(c)

51 (nm)(311)M

(220)M

(400)M

(422)M

(511)M

(440)M

(533)M

(731)M

(751)M

(d)






1

34

e1

e2

e3

52

100 (nm)

(a)

00

0

20

40

60

80

100

Pt

FeMnCr

OPt

Inte

nsity

Distance (microm)

Matrix

01 02 03 04

(b)

Positionin (a)


739

506 12883

186 531158

22254308

631321

(c)

(440)M

(400)M(311)M

51 (nm)

(d)

(440)M

(400)M

(311)M

51 (nm)

(e)



00 02 04 06 0845

50

55

60

65

70

75

REF 18Mn 18Mn5Cr

I(Fe

L3)

I(Fe

L2)



AR layer

NAR layer

M

δ + M

REF

(a)

M

18Mn

(b)

18Mn5Cr

M

(c)




5 Conclusions








Acknowledgments


References





























































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls











10 20 30 40 50 60 70 80 90

Inte

nsity

2θ

REF

SS

LorSS LL HG S

ZnO

L

(a)

10 20 30 40 50 60 70 80 90

Inte

nsity

2θ

18Mn

L L SGLG

HorG SSSS LL HG SL

ZnO

(b)

10 20 30 40 50 60 70 80 90

HH

Inte

nsity

2θ

18Mn5Cr

L L L GLG

HorG S SSSS S LL G

ZnO

(c)











1000 800 600 400 200

0

50

100

150

200

250

300

L

S

G

H

S

GG

LH

H

Rela

tive i

nten

sity

Wave number

HS

API 18Mn 18Mn5Cr

G








2θ

Normal

SS SS

(202)Fe(101)Fe

S

SS

SSS

(202)Fe(200)Fe(101)Fe

Thin

(200)Fe

REF

10 20 30 40 50 60 70 80 90

(a)

S SSS

(200)Fe

S

(101)Fe

SS

SSS

(311)Fe(220)Fe(101)Fe

NormalThin

(200)Fe

18Mn

10 20 30 40 50 60 70 80 902θ

(b)

(220)Fe

S SS

(200)Fe

S

(101)Fe (200)Fe

S

SSS

(311)Fe(220)Fe(101)Fe

NormalThin

18Mn5Cr

10 20 30 40 50 60 70 80 902θ

(c)







REF




e1

(b)

e2

e3

e4

e5

e6e7

2 1

200 (nm)

(a)

00 04 08 12

0

20

40

60

80

100

Pt

FeMn

OPt

Inte

nsity

Distance (μm)

Matrix

(b)

(110)δ or (440)M

(100)δ or (311)M

(102)δ or (511)M(002)δ

51 (nm)

(c)

(633)M(710)M(622)M(620)M(440)M

51 (nm)

(110)M(102)M(002)M (100)M(100)M

(d)






4 Discussion


5

123

4e3

e2

e1

(b)

02 (μm)

(a)

00 02 04 06 08

0

20

40

60

80

100

Pt

FeMn

OPt

Inte

nsity

Distance (μm)

Matrix

(b)

Positionin (a)


134184463343

19856

192250

12

43

(c)

51 (nm)(311)M

(220)M

(400)M

(422)M

(511)M

(440)M

(533)M

(731)M

(751)M

(d)






1

34

e1

e2

e3

52

100 (nm)

(a)

00

0

20

40

60

80

100

Pt

FeMnCr

OPt

Inte

nsity

Distance (microm)

Matrix

01 02 03 04

(b)

Positionin (a)


739

506 12883

186 531158

22254308

631321

(c)

(440)M

(400)M(311)M

51 (nm)

(d)

(440)M

(400)M

(311)M

51 (nm)

(e)



00 02 04 06 0845

50

55

60

65

70

75

REF 18Mn 18Mn5Cr

I(Fe

L3)

I(Fe

L2)



AR layer

NAR layer

M

δ + M

REF

(a)

M

18Mn

(b)

18Mn5Cr

M

(c)




5 Conclusions








Acknowledgments


References





























































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls












1000 800 600 400 200

0

50

100

150

200

250

300

L

S

G

H

S

GG

LH

H

Rela

tive i

nten

sity

Wave number

HS

API 18Mn 18Mn5Cr

G








2θ

Normal

SS SS

(202)Fe(101)Fe

S

SS

SSS

(202)Fe(200)Fe(101)Fe

Thin

(200)Fe

REF

10 20 30 40 50 60 70 80 90

(a)

S SSS

(200)Fe

S

(101)Fe

SS

SSS

(311)Fe(220)Fe(101)Fe

NormalThin

(200)Fe

18Mn

10 20 30 40 50 60 70 80 902θ

(b)

(220)Fe

S SS

(200)Fe

S

(101)Fe (200)Fe

S

SSS

(311)Fe(220)Fe(101)Fe

NormalThin

18Mn5Cr

10 20 30 40 50 60 70 80 902θ

(c)







REF




e1

(b)

e2

e3

e4

e5

e6e7

2 1

200 (nm)

(a)

00 04 08 12

0

20

40

60

80

100

Pt

FeMn

OPt

Inte

nsity

Distance (μm)

Matrix

(b)

(110)δ or (440)M

(100)δ or (311)M

(102)δ or (511)M(002)δ

51 (nm)

(c)

(633)M(710)M(622)M(620)M(440)M

51 (nm)

(110)M(102)M(002)M (100)M(100)M

(d)






4 Discussion


5

123

4e3

e2

e1

(b)

02 (μm)

(a)

00 02 04 06 08

0

20

40

60

80

100

Pt

FeMn

OPt

Inte

nsity

Distance (μm)

Matrix

(b)

Positionin (a)


134184463343

19856

192250

12

43

(c)

51 (nm)(311)M

(220)M

(400)M

(422)M

(511)M

(440)M

(533)M

(731)M

(751)M

(d)






1

34

e1

e2

e3

52

100 (nm)

(a)

00

0

20

40

60

80

100

Pt

FeMnCr

OPt

Inte

nsity

Distance (microm)

Matrix

01 02 03 04

(b)

Positionin (a)


739

506 12883

186 531158

22254308

631321

(c)

(440)M

(400)M(311)M

51 (nm)

(d)

(440)M

(400)M

(311)M

51 (nm)

(e)



00 02 04 06 0845

50

55

60

65

70

75

REF 18Mn 18Mn5Cr

I(Fe

L3)

I(Fe

L2)



AR layer

NAR layer

M

δ + M

REF

(a)

M

18Mn

(b)

18Mn5Cr

M

(c)




5 Conclusions








Acknowledgments


References





























































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls









2θ

Normal

SS SS

(202)Fe(101)Fe

S

SS

SSS

(202)Fe(200)Fe(101)Fe

Thin

(200)Fe

REF

10 20 30 40 50 60 70 80 90

(a)

S SSS

(200)Fe

S

(101)Fe

SS

SSS

(311)Fe(220)Fe(101)Fe

NormalThin

(200)Fe

18Mn

10 20 30 40 50 60 70 80 902θ

(b)

(220)Fe

S SS

(200)Fe

S

(101)Fe (200)Fe

S

SSS

(311)Fe(220)Fe(101)Fe

NormalThin

18Mn5Cr

10 20 30 40 50 60 70 80 902θ

(c)







REF




e1

(b)

e2

e3

e4

e5

e6e7

2 1

200 (nm)

(a)

00 04 08 12

0

20

40

60

80

100

Pt

FeMn

OPt

Inte

nsity

Distance (μm)

Matrix

(b)

(110)δ or (440)M

(100)δ or (311)M

(102)δ or (511)M(002)δ

51 (nm)

(c)

(633)M(710)M(622)M(620)M(440)M

51 (nm)

(110)M(102)M(002)M (100)M(100)M

(d)






4 Discussion


5

123

4e3

e2

e1

(b)

02 (μm)

(a)

00 02 04 06 08

0

20

40

60

80

100

Pt

FeMn

OPt

Inte

nsity

Distance (μm)

Matrix

(b)

Positionin (a)


134184463343

19856

192250

12

43

(c)

51 (nm)(311)M

(220)M

(400)M

(422)M

(511)M

(440)M

(533)M

(731)M

(751)M

(d)






1

34

e1

e2

e3

52

100 (nm)

(a)

00

0

20

40

60

80

100

Pt

FeMnCr

OPt

Inte

nsity

Distance (microm)

Matrix

01 02 03 04

(b)

Positionin (a)


739

506 12883

186 531158

22254308

631321

(c)

(440)M

(400)M(311)M

51 (nm)

(d)

(440)M

(400)M

(311)M

51 (nm)

(e)



00 02 04 06 0845

50

55

60

65

70

75

REF 18Mn 18Mn5Cr

I(Fe

L3)

I(Fe

L2)



AR layer

NAR layer

M

δ + M

REF

(a)

M

18Mn

(b)

18Mn5Cr

M

(c)




5 Conclusions








Acknowledgments


References





























































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls








REF




e1

(b)

e2

e3

e4

e5

e6e7

2 1

200 (nm)

(a)

00 04 08 12

0

20

40

60

80

100

Pt

FeMn

OPt

Inte

nsity

Distance (μm)

Matrix

(b)

(110)δ or (440)M

(100)δ or (311)M

(102)δ or (511)M(002)δ

51 (nm)

(c)

(633)M(710)M(622)M(620)M(440)M

51 (nm)

(110)M(102)M(002)M (100)M(100)M

(d)






4 Discussion


5

123

4e3

e2

e1

(b)

02 (μm)

(a)

00 02 04 06 08

0

20

40

60

80

100

Pt

FeMn

OPt

Inte

nsity

Distance (μm)

Matrix

(b)

Positionin (a)


134184463343

19856

192250

12

43

(c)

51 (nm)(311)M

(220)M

(400)M

(422)M

(511)M

(440)M

(533)M

(731)M

(751)M

(d)






1

34

e1

e2

e3

52

100 (nm)

(a)

00

0

20

40

60

80

100

Pt

FeMnCr

OPt

Inte

nsity

Distance (microm)

Matrix

01 02 03 04

(b)

Positionin (a)


739

506 12883

186 531158

22254308

631321

(c)

(440)M

(400)M(311)M

51 (nm)

(d)

(440)M

(400)M

(311)M

51 (nm)

(e)



00 02 04 06 0845

50

55

60

65

70

75

REF 18Mn 18Mn5Cr

I(Fe

L3)

I(Fe

L2)



AR layer

NAR layer

M

δ + M

REF

(a)

M

18Mn

(b)

18Mn5Cr

M

(c)




5 Conclusions








Acknowledgments


References





























































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls







4 Discussion


5

123

4e3

e2

e1

(b)

02 (μm)

(a)

00 02 04 06 08

0

20

40

60

80

100

Pt

FeMn

OPt

Inte

nsity

Distance (μm)

Matrix

(b)

Positionin (a)


134184463343

19856

192250

12

43

(c)

51 (nm)(311)M

(220)M

(400)M

(422)M

(511)M

(440)M

(533)M

(731)M

(751)M

(d)






1

34

e1

e2

e3

52

100 (nm)

(a)

00

0

20

40

60

80

100

Pt

FeMnCr

OPt

Inte

nsity

Distance (microm)

Matrix

01 02 03 04

(b)

Positionin (a)


739

506 12883

186 531158

22254308

631321

(c)

(440)M

(400)M(311)M

51 (nm)

(d)

(440)M

(400)M

(311)M

51 (nm)

(e)



00 02 04 06 0845

50

55

60

65

70

75

REF 18Mn 18Mn5Cr

I(Fe

L3)

I(Fe

L2)



AR layer

NAR layer

M

δ + M

REF

(a)

M

18Mn

(b)

18Mn5Cr

M

(c)




5 Conclusions








Acknowledgments


References





























































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls







1

34

e1

e2

e3

52

100 (nm)

(a)

00

0

20

40

60

80

100

Pt

FeMnCr

OPt

Inte

nsity

Distance (microm)

Matrix

01 02 03 04

(b)

Positionin (a)


739

506 12883

186 531158

22254308

631321

(c)

(440)M

(400)M(311)M

51 (nm)

(d)

(440)M

(400)M

(311)M

51 (nm)

(e)



00 02 04 06 0845

50

55

60

65

70

75

REF 18Mn 18Mn5Cr

I(Fe

L3)

I(Fe

L2)



AR layer

NAR layer

M

δ + M

REF

(a)

M

18Mn

(b)

18Mn5Cr

M

(c)




5 Conclusions








Acknowledgments


References





























































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls




00 02 04 06 0845

50

55

60

65

70

75

REF 18Mn 18Mn5Cr

I(Fe

L3)

I(Fe

L2)



AR layer

NAR layer

M

δ + M

REF

(a)

M

18Mn

(b)

18Mn5Cr

M

(c)




5 Conclusions








Acknowledgments


References





























































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls





5 Conclusions








Acknowledgments


References





























































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls












































Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls






Advances in



Journal of

Chemistry















Journal of





Volume 2018









Journal of


Na

nom

ate

ria

ls




Documents

EffectsofAlloyingElements(Cr,Mn)onCorrosionPropertiesof ...downloads.hindawi.com/journals/amse/2018/7638274.pdf · 18Mn5Cr>18Mn>REF, which corresponds with the change of the mean