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KkochNimOha,b,SooHoonAhnb,KwangSupEomc,KiMinJungb,HyukSangKwonb,⇑aSchoolofMaterialsScienceandEngineering,GeorgiaInstituteofTechnology,Atlanta,GA30332,USADept.ofMaterialsScienceandEngineering,KoreaAdvancedInstituteofScienceandTechnology,373-1,GuSeongDong,YuSeongGu,DaeJeon305-701,RepublicofKoreacSchoolofChemical&BiomolecularEngineering,GeorgiaInstituteofTechnology,Atlanta,GA30332,USAbarticleinfoabstract

ThestructureandcompositionofpassivefilmformedonFe–20Cr–xNi(x=0,10,20wt.%)alloysindeaer-atedpH8.5boratebuffersolutionwasexaminedbytransmissionelectronmicroscopeandCs-correctedscanningtransmissionelectronmicroscope-electronenergylossspectroscopy.Thicknessofthepassivefilmoneachalloywasmeasuredtobe2.5–2.7nmandthepassivefilmwasenrichedwithCr.Thepassivefilmformedonthealloysexhibitedanamorphousstructure,asconfirmedbythelackofdiffractioncon-trastandbythefastFouriertransformimagestakenwithinaregionofthepassivefilmoneachalloy.Ó2013ElsevierLtd.Allrightsreserved.Articlehistory:Received1July2013Accepted16October2013Availableonline26October2013Keywords:C.PassivefilmB.TEMB.STEM1.IntroductionTheexcellentcorrosionresistanceofstainlesssteels(SSs)ispri-marilyduetotheformationofprotectivepassivefilmontheirsteelsurface.Howeverthethicknessofthepassivefilmisonly2.5–4nm[1–4],andhenceitisverydifficulttodirectlyexaminetheextre-melythinpassivefilmwithitscompositionprofile.Thepassivefilmhavebeeninvestigatedusingvariousex-situtechniquessuchasX-rayphotoelectronspectroscopy(XPS)[1,5–25],ion-scatteringspectroscopy(ISS)[2],augerelectronspectroscopy(AES)[6,7,14],secondary-ionmassspectroscopy(SIMS)[6,7,25–28],andalsousinginsitutechniquessuchasphotoelectrochemicalspectros-copy(PES)[29–32],andscanningtunnelingmicroscopy(STM)[33–37].Althoughdetailsinthecompositionandstructureofthepassivefilmremainscontroversial,ithasbeengenerallyagreedthatthepassivefilmonFe–CrSSsconsistsofCr-enriched(Fe,Cr)oxidesand/orhydroxides[1–4].Kirchheimetal.[4]reportedbasedontheXPSinvestigationthatthecompositionofthepassivefilmformedonseveralFe–xCralloys(x=0.6–18at.%)in1NH2SO4solutionexhibitsastrongCrenrichmentintheoutermostlayerofthefilmdueprimarilytothepreferentialdissolutionofFeionsandalsotothelowermobilityofCrcomparedtothatofFeinthefilm.However,Hakikietal.[38]obtainedcompletelydifferentdepthprofilesforthepassivefilmformedon304and316SSsinpH9.2boratebuffersolutionusingAES.Theyobservedadistinctlyduplexlayerwith⇑Correspondingauthor.Tel.:+82423503326;fax:+82423503310.E-mailaddress:hskwon@kaist.ac.kr(H.Kwon).0010-938X/$-seefrontmatterÓ2013ElsevierLtd.Allrightsreserved.http://dx.doi.org/10.1016/j.corsci.2013.10.023innerCr-oxideandouterFe-oxide.Inaddition,Mitrovic-Scepa-novicetal.[39]examinedthepassivefilmformedonFe–26Cral-loyinpH2.0H2SO4solutionbyAES,andsuggestedthatthefilmwascomposedofeithera(Fe,Cr)2O3-typeoxide(singlelayer)orduplexlayerwithaninnerFeCr2O4layerandanouter(Fe,Cr)2O3layerdependingonthefilmformationpotential.Moreover,Mau-riceetal.[35]reportedthatageingunderpolarizationpromotesformationofacrystallinestructureofthepassivefilmsformedon(100)Fe–18Cr–13Nisingle-crystalsurfacein0.5MH2SO4solutionexaminedusingSTM.Furthermore,amorphousstructureisobservedatshortpolarizationtimes[34–36].However,thetechniquesmentionedabovesuchasXPSandAEShavebeenre-portedtohavesufficientsensitivityanddepthresolutiontoinves-tigatethenm-thickpassivefilms,whilethelateralresolutionisnobetterthanseveraltensofnm,whichisalimitingfactorinclarifyingthenmtosub-nmcompositionalfluctuationofpassivefilmsonSSs[40].Recently,severalresearchershavedirectlyobservedtheinter-nalstructureofthepassivefilmusingascanningtransmissionelectronmicroscope(STEM)[40,41].Hamadaetal.[40]andKuma-gaietal.[41]claimedthatthepassivefilmofSSssuchastype304andhighnitrogensteelexhibitsanamorphousstructurebasedontheirexperimentalresultsthatnodiffractioncontrastwasob-tainedwithinthepassiveregion;however,theauthorsprovidedonlythediffractioncontrastofthepassivefilm,andhencemoreevidenceisneededtoclarifythestructureofthepassivefilm.Intheirstudies,theyusedaCcoating,whichhasanamorphousstruc-ture,toprotectthesurfaceofthepassivefilmduringFIB-milling,andhencethestructureofeachregion(thepassivefilmandCcoat-K.Ohetal./CorrosionScience79(2014)34–40Table1Chemicalcompositions(wt.%)ofFe–20Cr–xNi(x=0,10,20wt.%)alloysanalyzedbyEDS.FeFe–20CrFe–20Cr–10NiFe–20Cr–20NiBal.Bal.Bal.Cr20.6519.7919.67Ni–10.0520.1035ing,bothareamorphous)cannotbedistinguishedbyFFT(FastFou-rierTransform)imagewhichisagoodanalysistechniquetoinves-tigatethecrystallinityofmaterials.Therefore,PtcoatingwithpolycrystallinestructurewouldbepreferredtotheCcoatingonthesurfaceofthepassivefilmtoobtaindifferentFFTimagesofboththepassivefilmandthePtcoatingregionforbettercharacter-izationofpassivefilm.Furthermore,toelucidatethecompositionatthesub-nmlateralscalewithcross-sectionalimagesofthepas-sivefilm,Cs-correctedSTEM–EELSwasusedbecauseitispowerfultoolforatomic-scaleanalysis,andalsoithasasignificantadvan-tageinsub-nminvestigationsbecauseitcanfocustheelectronbeamtoasub-nmsizewhilemaintainingahighprobecurrent[40].ItisanobjectiveofthepresentworktoexaminethestructureandcompositionofpassivefilmformedonFe–20Cr–xNi(x=0,10,20wt.%)alloys,withafocusontheeffectsofNionthepassivefilm.ThestructureandcompositionofthepassivefilmformedonFig.1.ThepotentiostaticpolarizationresponsesofFe–20Cr–xNi(x=0,10,20wt.%)alloysindeaeratedpH8.5boratebuffersolutionat50°C:(a)theappliedpotentialusedinthepotentiostaticpolarizationtestsand(b)thecurrenttransientcurvesforeachalloy.Fig.2.Schematicoftheprocedureusedforthecross-sectionTEMsamplepreparationofFe–20Cralloy:(a)DepositionofPtonthesurfaceofFe–20Cralloy;(b)trench-millingoneachsideofthePtdepositionregion;(c)separationofthecross-sectionalsampleofeachFe–20Cralloyand(d)TEMimageofthecross-sectionalTEMsampleofFe–20CralloymilledusingFIB.36K.Ohetal./CorrosionScience79(2014)34–40thealloyswascharacterizedusingTEMandCs-correctedSTEM–EELS.2.ExperimentalTheFe–20Cr–xNi(x=0,10,20wt.%)alloyswerepreparedbyvacuumarcmeltingandthencastintheformofabutton.Thecastwashomogenizedfor120minat1200°Candthenhot-rolledintoa3mmthickplate.Thespecimenswerepreparedbycoldrollingthehot-rolledplatesto1.6mmthicksheetsandthenannealedfor30minat1050°C,followedbyquenchinginwater.ThechemicalcompositionsofthealloysaregiveninTable1.Forelectrochemicaltests,specimensweregroundwithSiCpaperto2000grit,polishedwith1lmdiamondsuspension,andthenultrasonicallycleanedwithethanol.PotentiostaticpolarizationtestswereconductedtoformthepassivefilmsonFe–20Cr–xNi(x=0,10,20wt.%)alloysindeaer-atedpH8.5boratebuffersolutionat50°C.Theelectrochemicalcellforthetestswasequippedwithaplatinumcounterelectrode,asaturatedcalomelreferenceelectrode(SCE),andatestspecimenasaworkingelectrode.TheworkingelectrodewascathodicallycleanedbypolarizationtoÀ1.0VSCEfor300s,andthentheappliedpotentialwassteppedtoafilmformationpotentialof0.4VSCEatwhichpassivefilmwasformedpotentiostaticallyfor12hasshowninFig.1andthepotentiodynamicpolarizationresponsesofFe–20Cr–xNi(x=0,10,20wt.%)alloysareshownintheinsetofFig.1(b).ThicknessofpassivefilmonironbasealloysisdependentonpH,appliedpotentialandsolutiontemperature.AccordingtoHaandKwon[42],thethicknessofthepassivefilmreachedamaxi-mumatpH8.5$9invariouspH7$11boratebuffersolutions;theyalsofoundthatfilmsformedatpH8.5$9werethemostpro-tectiveandexhibitedthelowestdefectdensity.Moreover,thethicknessofthepassivefilmincreaseswithanincreaseinthefilmformationpotential[43]andthesolutiontemperature[44].Hence,thetestingconditionsemployedinthisworkfortheformationofpassivefilmweretoformathickerandmoreprotectivepassivefilm.Afterthefilmwasformed,thesampleswerestoredinavac-uumdesiccatortoavoidanyreactionwithatmosphericmoisture.Thecross-sectionTEMsamplesofthepassivefilmformedonFe–20Cr–xNi(x=0,10,20wt.%)alloyswerepreparedusingadual-beamfocusedionbeam(DB-FIB,NOVA200byFEI)atanaccelerat-ingvoltageof30kV,followingthedepositionofaPtlayertoprotectthesurfaceofthealloys.Fig.2showsaschematicprocedureforthepreparationofcross-sectionalTEMsampleofFe–20Cralloyonwhichpassivefilmwasformedat0.4VSCEfor12hindeaerated,50°C,pH8.5boratebuffersolution.Fig.2(a–c)areFIBmicroscopeFig.3.TEMimagesofthecross-sectionalTEMsamplesofFe–20Cr–xNi(x=0,10,20wt.%)alloysonwhichapassivefilmwasformedindeaerated,50°C,pH8.5boratebuffersolutionat0.4VSCEfor12h:(a)Fe–20Cralloy,(b)Fe–20Cr–10Nialloyand(c)Fe–20Cr–20Nialloy.K.Ohetal./CorrosionScience79(2014)34–4037imagestakenduringthecross-sectionalTEMsamplepreparationusingFIBmilling,andFig.2(d)isaTEMimageofthecross-sectionalTEMsampleofFe–20Cralloy.BeforetheFIBmillingofthealloy,Ptwasdepositedonthepassivefilmofthealloysusingasputtercoat-er(LeicaEMSCD005),showninFig.2(a),toenhancethesurfaceconductivityandalsotoprotectthealloysurfaceduringFIBmilling.Particularly,DB-FIBwithtwoindependentmicroscopecolumnsforafocusedionbeamandanelectronbeamwasused.Anelectron-beam-depositedlayerhasbeenreportedtobepreferabletoanion-beam-depositedlayerdueprimarilytothefactthatthemetalparticlesformedintheelectron-beamdepositedlayeraresmallerbysmoothermillingconditionthatismorefavorableforprotectionofthepassivefilm[45].Hence,theuseoftheionbeamistypicallyavoidedwhentheregionofinterestisclosetothepassivefilmtobeexamined[45].Therefore,theinitialPtlayerwasdepositedonthepassivefilmoftheFe–20Cr–xNi(x=0,10,20wt.%)alloysusinganelectronbeamtotheminimumthicknessof100nm,andthenthefinalPtlayerwassubsequentlydepositedwiththeionbeamtothethicknessof1lm.Trench-millingwasthenperformedusingFIBoneachsideofthePt-depositionregionshowninFig.2(bandc),andaPt-depositedcross-sectionalsampleofthealloyswasat-tachedtoaTEMgrid,followedbyFIBmillingtoamaximumthick-nessof50nm.Fig.2(d)showsaTEMimageofthecross-sectionalTEMsampleofFe–20Cralloy.Thecross-sectionalimageofthepassivefilmformedonFe–20Cr–xNi(x=0,10,20wt.%)alloyswascharacterizedusingTEM(TecnaiG2F30S-TwinbyFEIoperatedat300kV),andthechemicalcompositionofthepassivefilmswasinvestigatedbyEELS(Gatan)equippedwithCs-correctedSTEM(JEM-ARM200FbyJEOL)oper-atedatanacceleratingvoltageof200kV.TheprobecurrentoftheEELSelectrongunwas0.5nAforaprobediameterof0.2nm.3.Resultsanddiscussion3.1.Thecross-sectionalimagesandthecompositionofthepassivefilmsontheFe–20Cr–xNi(x=0,10,20wt.%)alloysFig.3showsTEMimagesofthecross-sectionalTEMsamplesoftheFe–20Cr–xNi(x=0,10,20wt.%)alloysofwhichpassivefilmshavebeenformedfor12hindeaerated,50°C,pH8.5boratebuffersolutionat0.4VSCE.FourlayerscomprisingadepositedPtwithanelectronbeam,asputter-coatedPt,apassivefilm,andthemetalwereobservedineachalloy.Inparticular,thethicknessofthethirdlayerorthepassivefilmisintherangeof2.5–3nm,similartothatofthepassivefilmofFe–Cralloys[1–4].However,thediffractionpatternswerenotclearlyobservedinthemetalphaseofFig.3(aandb)duetomagneticpropertiesofFe–20CrandFe–20Cr–10Nialloys.ForFe–20Cr–10Nialloy,ithassmallmagneticpropertyeventhoughitisanausteniticstainlesssteelhenceitwashardtoob-serveaclearimageinboththemetalphaseandthepassivefilm.Fig.4showsSTEMimagesandenergy-dispersiveX-rayspectrom-eter(EDS)lineprofilesalongtheredarrowdrawnoneachSTEMimageofthecross-sectionalTEMsampleoftheFe–20Cr–xNi(x=0,10,20wt.%)alloys.Accordingtothelineprofilesforeachal-loy,layer1andlayer2inFig.4areconfirmedtobePtlayersdepos-itedusinganelectronbeamandusingasputtercoater,respectively.Inaddition,layer4indicatesthebasemetal.However,asufficientoxygensignalwasnotdetectedinthelayer3orinthepassivefilm,whichwasexpectedtocontainsignificantamountsofoxygeninthepassivefilm.Thelackofoxygeninthefilmlayerwasdueprobablytothefactthatoxygenistoolightelementtobeeasilydetected,andhencethefourlayersappeartobeonlythreelayers.Therefore,STEM–EELSwasusedtodetecttheoxygensignalfromthelayer3.Electronenergylossspectroscopy(EELS)isacomplimentarytechniqueemployedwithhigh-resolutiontransmissionelectronmicroscopyforperformingelementalanalysisonthenanometerscale[46];italsofeatureshigherdetectionsensitivitythanEDSforlightelements[47]andisthereforeagoodmethodforthedetectionfortheoxygenfromthelayer3.Fig.5showsanexampleofaCs-correctedSTEMimageandEELSspectrumofFe–20Cr–10Nialloy.FortheCs-correctedSTEMimageinFig.5(a),theblack-col-oredlayerwhichsuggestedthatthepassivefilmwasobserved;thislayerwasnotobservedintheSTEMimageinFig.4.Toconfirmtheexistenceofasufficientoxygensignalintheblack-coloredlayer,EELSwasconductedalongtheredarrowinFig.5(a),andisFig.4.STEMimagesandEDSlineprofilesalongtheredarrowintheSTEMimageofthecross-sectionalTEMsampleofFe–20Cr–xNi(x=0,10,20wt.%)alloys:(a)Fe–20Cralloy,(b)Fe–20Cr–10Nialloyand(c)Fe–20Cr–20Nialloy(Forinterpretationofthereferencestocolorinthisfigurelegend,thereaderisreferredtothewebversionofthisarticle.).38K.Ohetal./CorrosionScience79(2014)34–40presentedinFig.5(b)whichshowstheexistenceofO–K,Cr–L2,3,Fe–L2,3,andNi–L2,3peaksinthatlayer.Andalso,theEELSdatacol-lectedalongthebluearrowwereconvertedintoasignalprofileusingtheGatansoftwarepackage,andtheresultsarepresentedinFig.6.AccordingtoFig.6,asufficientoxygensignalprofilewasobservedascomparedtotheEDSlineprofilesinFig.4,whichconfirmedthatlayer3inFigs.3and4isthepassivefilmoftheFe–20Cr–xNi(x=0,10,20wt.%)alloys.ThethicknessofthepassivefilmoneachalloywasdeterminedbasedontheFWHM(full-widthathalf-maximum)oftheoxygensignalprofile,anditwasesti-matedtobe2.5–2.7nmthick,asshownintheinsetofFig.6.FortheCrsignalprofileintheregionofthepassivefilmofeachalloy,theCrenrichmentagreedwiththeresultsofotherresearchers[2,31,40].However,interestingly,theNisignalwasnotdetectedintheregionofthepassivefilmintheFe–20Cr–10Nialloy,andarelativelysmallamountofNicomparedtotheNisignalintheme-talphaseofFe–20Cr–20NialloywasobservedinthepassivefilmofFe–20Cr–20Nialloy.ThisphenomenonhasalsobeenreportedbyHamadaetal.[40],whoalsofoundthatNiwasnotdetectedattheoutermostsurfaceinthecaseoftheSTEM–EDSlineprofileof304SS,whichiscomposedof18wt.%Crand8wt.%Ni.Theyre-portedthatthereasonwhytheNiwasnotdetectedattheouter-mostsurfaceisdueprincipallytoitsrelativelylowoxygenaffinitycomparedtothatofFeandCr,whereasCrenrichmentoc-curseasilybecauseofitshighoxygenaffinity[40].Consequently,Niremainsinthemetalphaseofeachalloy;however,withanin-creaseintheNicontent,thecontributionofNitothepassivefilmincreases,asshowninFig.6(bandc).3.2.ThestructureofthepassivefilmonFe–20Cr–xNi(x=0,10,20wt.%)alloysFig.7showstheTEMandFFT(fastFouriertransform)imagesofFe–20Cr–xNi(x=0,10,20wt.%)alloysofwhichpassivefilmswereformedindeaerated,50°C,pH8.5boratebuffersolutionat0.4VSCEfor12h.RegionsA,B,andCrepresentametal,apassivefilm,andasputter-coatedPtlayer,respectively.RegionB,inparticular,showedanamorphousstructureornodiffractioncontrastwithinthepassivefilmofFe–20Cr–xNi(x=0,10,20wt.%)alloys.Tocon-firmitfurther,weusedPtcoatinginsteadofCcoating[40,41]toobtainthreetypesofFFTimagessuchascrystallineformetalphase,amorphousforthepassivefilm,andpolycrystallineforPtcoatingfromoneTEMimage.AccordingtotheFFTimagesofregionFig.6.EELSsignalprofilesofFe–20Cr–xNi(x=0,10,20wt.%)alloys:(a)Fe–20Cralloy,(b)Fe–20Cr–10Nialloyand(c)Fe–20Cr–20Nialloy.Bineachalloy,thepassivefilmshowedanamorphousstructure,whereasregionA(themetal)andregionC(thesputter-coatedPtlayer)haveacrystallineandapolycrystallinestructure,respec-tively.However,somewhitedotswerestilldetectedinFFTimagesoftheregionBasshowninFig.7,butthereasonwhyitwasob-servedispresumablyduetothePtparticlesand/ormetalinmetalphaseduringFIBmilling.ItishardtocontrolthePtmillingsincethethicknessofthepassivefilmsareonly2–3nm,andhencePtparticlesand/ormetalinmetalphasewereeasilystuckonthepas-sivefilmregion.Fig.5.(a)TheCs-correctedSTEMimageand(b)theEELSspectrumalongtheredarrowintheCs-correctedSTEMimageofthecross-sectionalTEMsampleofFe–20Cr–10Nialloy.K.Ohetal./CorrosionScience79(2014)34–4039Fig.7.TEMandFFTimagesofFe–20Cr–xNi(x=0,10,20wt.%)alloysonwhichapassivefilmhasbeenformedindeaerated,50°C,pH8.5boratebuffersolutionat0.4VSCEfor12h.4.ConclusionsInthisstudy,wedirectlyobservedthepassivefilmformedonFe–20Cr–xNi(x=0,10,20wt.%)alloysindeaeratedpH8.5boratebuffersolutionusingTEMandCs-correctedSTEM–EELS.Ontheba-sisoftheresults,wedrawthefollowingconclusions:(1)WedirectlyobservedthepassivefilmofFe–20Cr–xNi(x=0,10,20wt.%)alloys,andthecompositionofthefilmwascon-firmedbyEELS.Thethicknessofthepassivefilmoneachalloywasestimatedtobe2.5–2.7nmthick,andtheCrenrichmentwasobserved.However,NisignalwasnotdetectedinthepassivefilmofFe–20Cr–10Nialloy,whilearelativelysmallamountofNicomparedtotheNiinthemetalphaseofFe–20Cr–20Nialloywasobservedinthepas-sivefilmofFe–20Cr–20Nialloy.(2)ThepassivefilmformedontheFe–20Cr–xNi(x=0,10,20wt.%)alloysinpH8.5boratebuffersolutionat50°Cexhibitsanamorphousstructurebasedonthelackofdiffrac-tioncontrastandontheFFTimagestakenwithintheregionofthepassivefilmofeachalloy.AcknowledgementTheauthorsgratefullyacknowledgethesupportofPOSCOsteelandtheBrainKorea(BK21)projectinthesuccessfulcompletionofthisproject.References[1]V.Maurice,W.P.Yang,P.Marcus,XPSandSTMstudyofpassivefilmsformedonFe–22Cr(110)single-crystalsurfaces,J.Electrochem.Soc.143(1996)1182–1200.[2]S.Haupt,H.-H.Strehblow,AcombinedsurfaceanalyticalandelectrochemicalstudyoftheformationofpassivelayersonFe/Cralloysin0.5MH2SO4,Corros.Sci.37(1995)43–.[3]L.J.Oblonsky,M.P.Ryan,H.S.Isaacs,InsitudeterminationofthecompositionofsurfacefilmsformedonFe–Cralloys,J.Electrochem.Soc.145(1998)1922–1932.[4]R.Kirchheim,B.Heine,H.Fischmeister,S.Hofmann,H.Knote,U.Stolz,Thepassivityofiron–chromiumalloys,Corros.Sci.29(19)9–917.[5]HeliWang,JohnA.Turner,Ferriticstainlesssteelsasbipolarplatematerialforpolymerelectrolytemembranefuelcells,J.PowerSources128(2004)193–200.[6]S.Mischler,A.Vogel,H.J.Mathieu,D.Landolt,ThechemicalcompositionofthepassivefilmonFe–24CrandFe–24Cr–11MostudiedbyAES,XPSandSIMS,Corros.Sci.32(1991)925–944.[7]D.Landolt,S.Mischler,A.Vogel,H.J.Mathieu,ChlorideioneffectsonpassivefilmsonFeCrandFeCrMostudiedbyAES,XPSandSIMS,Corros.Sci.31(1990)431–440.[8]L.A.S.Ries,M.DaCunhaBelo,M.G.S.Ferreira,I.L.Muller,ChemicalcompositionandelectronicstructureofpassivefilmsformedonAlloy600inacidicsolution,Corros.Sci.50(2008)676–686.[9]Rock-HoonJung,HiroakiTsuchiya,ShinjiFujimoto,XPScharacterizationofpassivefilmsformedonType304stainlesssteelinhumidatmosphere,Corros.Sci.58(2012)62–68.[10]A.Alamr,D.F.Bahr,MichaelJacroux,Effectsofalloyandsolutionchemistryonthefractureofpassivefilmsonausteniticstainlesssteel,Corros.Sci.48(2006)925–936.[11]N.Padhy,RanitaPaul,U.RanitaPaul,BaldevRaj,Morphologicalandcompositionalanalysisofpassivefilmonausteniticstainlesssteelinnitricacidmedium,Appl.Surf.Sci.257(2011)5088–5097.[12]CongQianCheng,JieZhao,TieShanCao,QinQinFu,MingKaiLei,DeWeiDeng,Facilechromaticityapproachfortheinspectionofpassivefilmsonausteniticstainlesssteel,Corros.Sci.70(2013)[13]IngridMilošev,Gregorˇ235–242.Zerjav,JoseMariaCalderonMoreno,MonicaPopa,Electrochemicalproperties,chemicalcompositionandthicknessofpassivefilmformedonnovelTi–20Nb–10Zr–5Taalloy,Electrochim.Acta99(2013)176–1.[14]V.Vignal,H.Krawiec,O.Heintz,D.Mainy,Passivepropertiesofleanduplexstainlesssteelsafterlong-termageinginairstudiedusingEBSD,AES,XPSandlocalelectrochemicalimpedancespectroscopy,Corros.Sci.67(2013)109–117.[15]J.Högström,W.Fredriksson,K.Edstrom,F.Björefors,L.Nyholm,Claes-OlofA.Olsson,Cationprofilingofpassivefilmsonstainlesssteelformedinsulphuricandaceticacidbydeconvolutionofangle-resolvedX-rayphotoelectronspectra,Appl.Surf.Sci.284(2013)700–714.[16]X.Feng,Y.Zuo,Y.Tang,X.Zhao,J.Zhao,Theinfluenceofstrainonthepassivebehaviorofcarbonsteelincementextract,Corros.Sci.65(2012)2–8.[17]X.Zhang,D.Zagidulin,D.W.Shoesmith,CharacterizationoffilmpropertiesontheNi-Cr-MoAlloyC-2000,Electrochim.Acta(2013)814–822.[18]Z.J.Zheng,Y.Gao,Y.Gui,M.Zhu,Corrosionbehaviorofnanocrystalline304stainlesssteelpreparedbyequalchannelangularpressing,Corros.Sci.(2012)60–67.40K.Ohetal./CorrosionScience79(2014)34–40[19]P.Ju,Y.Zuo,Y.Tang,X.Zhao,Theenhancedpassivationof316Lstainlesssteelinasimulatedfuelcellenvironmentbysurfaceplatingwithpalladium,Corros.Sci.66(2013)330–336.[20]M.P.Short,R.G.Ballinger,H.E.Hänninen,CorrosionresistanceofalloysF91andFe–12Cr–2Siinlead-bismutheutecticupto715°C,J.Nucl.Mater.434(2013)259–281.[21]Y.Wang,S.L.Jiang,Y.G.Zheng,W.Ke,W.H.Sun,J.Q.Wang,ElectrochemicalbehaviorofFe-basedmetallicglassesinacidicandneutralsolutions,Corros.Sci.63(2012)159–173.[22]C.A.DellaRovere,J.H.Alano,R.Silva,P.A.P.Nascente,J.Otubo,S.E.Kuri,Characterizationofpassivefilmsonshapememorystainlesssteels,Corros.Sci.57(2012)1–161.[23]D.P.Wang,S.L.Wang,J.Q.Wang,RelationshipbetweenamorphousstructureandcorrosionbehaviorinaZr–Nimetallicglass,Corros.Sci.59(2012)88–95.[24]X.Zhang,D.W.Shoesmith,InfluenceoftemperatureonpassivefilmpropertiesonNi–Cr–MoAlloyC-2000,Corros.Sci.76(2013)4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