DOC

Effect_5

By Leonard Rose,2014-07-23 14:14
14 views 0
Effect_5Effect

    Effect

Dec.2008,Volume2,No.12(SerialNo.13)JournalofMaterialsScienceandEngineering,ISS

    N19348959,USA

    ;EffectofNaCIdepositonthecorrosionbehavior

    ;ofCuBiAIalloyat700900~C

    ;ZHANGRui-jun1.

    ;CHENLing2GUANLei3.

    ;LIUXiao.cuii

    ;.

    ;LIUJianhual

    ;StateKeyLaborato~ofMetastableMaterialsScienceandTechnology,YanshanUniversity

    ,Qinhuangdao066004,China

    ;2.DepartmentofEnvironmentalandChemicalEngineering,YanshanUniversi~,Qinhuan

    gdao06600,China,

    ;3.QinhuangdaoAnyePrecisionCastingCoLtd,Qinhuangdao066004,China) ;Abstract:TheeffectofNaCldepositonthecorrosionbehavior ;ofCuBiAlalloyat700.900?wasstudiedbymeansof

    ;metalloscope.XRD.SEM/EDXandthermograimetric.The ;resultsshowthatinairwithoutNaCI,theweightgainofsample ;wassmal1duetotheformationofacompactandunifoITnoxide ;protectivescale.However.withasolidNaCIdepositonits ;surface.thecorrosionofCuBiA1alloyinairwasobviously ;accelerated,andAlwaseasiertobeerodedthanCu.bywhich. ;chromiumdepletionisdevelopedinthesurfaceofalloybeneath ;theNaC1depositOntbebasisofwhich.acceleration ;mechanismsofNaC1onthecorrosionofCuBiAlalloywerealso ;discussed.

    ;Keywords:CuBiAlalloy;NaCl;corrosion

    ;1.Introduction

    ;Aluminumbronzehashighstrength,excellent

    ;thermalconductionperformanceandcorrosion

    ;resistance,soitisappliedwidelytothethermal ;exchangematerialofcondensetubeinelectricpower ;plantandshipping,andotherpartswithwearresisting

    ;andcorrosionresistanceproperties.Recently,therehas ;beenmanyresearchesandreportsaboutthecorrosion ;behaviorofaluminumbronzeinthemedium[_4].and ;arcsprayedduplexaluminumbronzebasedcoatings ;hashighoxidationresistanceHowever,

    ;few

    ;instanceswerereportedabouthightemperature ;corrosionofaluminumbronze.

    ;Duringtheservicelifeofsomecondensetube, ;boilersuperheattubeandotherpartsoxidationand

    ),male, ;Correspondingauthor:ZHANGRui-jun(1962

    ;professor;researchfield:metallicmaterials.E.mail: ;Zhangrj@ysu.edu.cn.

    ;corrosionwilloccurfortheworkingtemperatureistoo ;high,andtheprocesswillbeacceleratedforthe ;depositionofsaItonthesurface[6-7..AsNaCIisa ;typicalcompositioninchloridedeposit,thecorrosion ;behaviorOfCuBiAlalloywithoutorwithNaCldeposit ;at700and900?wasstudiedinthisarticle.andthe

    ;corrosionmechanismwasalsoanalyzed.

    ;2.Experimentalmethod

    ;ThetestedmaterialisCuBiAlalloy.with

    ;chemicalcomposition(massfraction%1of89.12Cu, ;0.32Bi.10-33Aland0.23others.Thesizeofsamplesis ;10mmx10mm~5mm.Beforeexperiment.allsurfaces ;ofthesampleswerepolishedto1000#withthe ;abrasivepaper,degreasedwithalcoholandwarlTledup, ;andthen.chemicalpureNaClsolutionwasspreadon ;theirsurfacesevenly,anddriedtoachieveabout ;3mg/cmsalt.Thesampleswereputintoaquartz ;crucibleandheatedinelectricresistancefumace ;SX_4.10to700and900?.Atieracertaintime.the

    ;quartzcruciblewiththesamplewastakenoutand ;cooleddowntoroomtemperature.Themasschange ;wasmeasuredbyESJ205.4photoelectricbalance ;(0.1mgprecision).Appearance,content,andphaseof ;corrosionproductiononthesurfaceandsectionofthe ;sampleswereobservedandanalyzedbvEOPHOT2l ;metalloscope,D/maxrBXRD.ADVANTPXP38l

    ;x-raysfluoroscope,andKYKY2800SEM/EDX.

    ;3.Resultsanddiscussion

    ;3l

    ;EffectofNaC!depositonthecorrosionbehaviorofCuBiAIalloyat700?900*(2

    ;3.1Corrosionkinetics

    ;CorrosionkineticcurvesoftheCuBiA1alloywith ;NaC1depositat700and900~CareshowninFig.1. ;ComparedwiththesamplewithNaC1deposit,the ;corrosionrateincreaseissmallermanthatofthe ;samplewithoutNaCIdeposit,whichdemonstratesthat ;thelattersamplehasbetterhightemperaturecorrosion

    ;resistanceproperty.ItmeansthatNaCIdepositcan ;acceleratethehightemperaturecorrosionofthe ;CuBiA1alloy,andthecorrosionrateincreaseismore ;signifcantathighertemperature.Fromthecurvesof ;corrosionkinetics,thecorrosionrateishighinitially ;andthendecreasesgradually.

    ;

    ;?

    ;

    ;.

    ;U

    ;

    ;Fig.1CorrosionkineticsoftheCuBiAIalloy ;Fig.2MierostructuresoftheCuBiAIalloy ;3.2Morphologyofcorrosion

    ;Fig.2illustratestheorganizationoftheCuBiAl ;alloy.Itcanbeseenthatthemicrostructureofthe

    castalloymainlyconsistsofirregularwhiteregion ;as

    ;andblackregion.XRD(Fig.3(a))andEDXanalysis ;illustratethatthewhiteregionisCusolidsolution

    ;32

    ;andtheblackregionaremainlyu-Cusolidsolution. ;A1Cu3,andA14Cu9.

    ;Macroscopicalobservationshowsthatonthe ;surfaceofthesamplewithoutNaC1depositacompact ;anduniforillblackoxidefilmformsat700?一900?.

    ;thecolorofthesamplesurfaceisunchangedafterthe ;oxidefilmfallingoff.TheXRDpattemindicatesthat ;theoxidefilmsonthesurfaceareCuO,Cu2O,and ;A1203.Comparatively,onthesurfaceofthesample ;withNaCldeposittheformedoxidelmisloose.the ;colorofthesurfacewhichcontactedwiththeoxide ;filmispurple.XRDpatteminFig.3(b)indicatesthat ;thesurfaceofthesamplewithNaCldepositisCuwhen ;theoxidelayerhasfallenoffFormSEM(Fig.4, ;observationsitcanbeseenthatthesurfaceiscorroded ;moreseverelyforthesamplewithNaC1deposit,and ;therearemanycracksandholesintheoxidefilmand ;theinterfacebetweenthet5lmandthealloysubstrate. ;7000

    ;6000

    ;5000

    ;?

    ;4000

;3000

    ;2000

    ;1000

    ;0

    ;20406080l00120

    ;20/(.1

    ;Fig.3Xraydiffractionpattern

    Notes:(a)israwmaterial;(b)issurfacesofsamples ;

    ;whoseoxidelayerhasfalloff(withNaCI).

    ;EffectofNaCIdepositonthecorrosionbehaviorofcu!!!:!!

    ;Fig.4CorrosionmorphologyofCuBiAIalloy ;(oxidizedat700”Cfor4h,

    ;Notes:(a)issurfacemorphologyofsampleswhoseoxide ;layerhasfalloff(withoutNaCI);(b)issurfacemorphologyof ;sampleswhoseoxidelayerhasfalloff(withNaC1);(c,is ;cross.sectionmorphologyofsampleswhoseoxidelayerhasn’t

    ;fal1off(withNaCI).

    ;EDS(Fig.5)resultshowsthatmuchCIemerges ;onthecorrosionzonesatthebordersbetweentheoxide ;layerandmatrix.Byanalyzingthesurfaceofthe ;samplesbyXray(Table1),comparedtotheoriginal ;sample,thecontentsofCudecreasesandthecontents ;OfAlincreasesforthesurfaceofthesamplewithout ;NaCldeposit.butthecontentsofCuincreases,the ;contentsofAldecreasesandthereissomeC1forthe ;surfaceofthesamplewithNaCldeposit.Thisindicates ;thatCuiscorrodedeasilywhenthesamplewithout ;NaCIdepositunderhightemperatureoxidation,butA1

    ;iscorrodedpriortoCuwiththeeffectofNaCldeposit ;andCltakespartintheprocessofcorrosion. ;Table1Resultsofx_raysfluoroscope(massfraction,%) ;E/keV

    ;Fig.5EDSanalysisresultsfrombordersbetween ;theoxidelayerandmatrixofCuBiAIahoy

    ;3.3Discussion

    ;TheCuBiAIiseasilyoxidedathightemperature, ;formingCuO,Cu20andA1203layeronthesurfaceofthe ;sample.Theformedcompactandstableoxidelayercan ;stopOdiffuseintothematrixandstopthealloybeing ;oxidedmore,sotheincreasedweightofthesample ;withoutNaC1depositissmallforthehightemperature ;oxidationisfewer.Fromtheexperiment,wecanseethat ;thecontentsofCudecreasebutthecontentsofAl ;increaseforthesurfaceofthesamplewithoutNaCl

    ;deposit.Thismainlybecausethecompactionandstability ;ofCuOandCu20layerislessthanA1203layer,thenO ;canpene~atetheCuOandCu20coatingmakingCu ;oxided.ButlessAIbeoxided,soAlinCuBiAlalloycan ;raiseoxidizingcorrosionresistancewithouttheeffectof ;NaC1depositNaC1reactwithA1203onthesurfaceof ;thesample2NaCI+A1203+1/202=Na2A1204+C12when ;CuBiAlalloywithNaC1deposit,givingoutC12.Usually ;C12hasbeaerpermeationthanOintheoxidedlayer,so ;C1,hass~ongercorrosion,itcanreactwithmetal ;penegatingtheoxidedlayerintothebordersoftheoxided ;layerandmatrix.Fromthethermodynamic,itisseenthat ;A1combinewithClmoreeasilythanCu.soAlisoxided ;preferentially.ThereactionisA1+3/2C12=A1C13,and ;A1C11willvolatilizetotheinterfaceofoxidedlayerand ;airatthetemperaturebecauseofit’shighlyvolatility.

    ;33

    ;

    ;E

    ;

    ;ff

    ;

    ;e

    ;

    ;c

    ;

    ;t

    ;

    ;o

    ;

    ;f

    ;

    ;N

    ;

    ;a

    ;

    ;C

    ;

    ;I

    ;

    ;d

    ;

    ;e

    ;

;p

    ;o

    ;

    ;s

    ;

    ;it

    ;

    ;o

    ;

    ;nthecorrosionbehaviorofCuBiAIalloyat700—900”12

    ;CualsocancombinewithCI(Cu+CI2=CuCI2),butless ;thanthatofA1.111esurfaceofthesampleconsistsofpoor ;A1anditappearspurple.AICI3isoxidedagainduring ;diffusingtooutside2A1C13+3/202=A12O3+3C12,someC12, ;whichformfromthereactionreactwithAIagaininthe ;bordersofoxidedlayerandmatrixuntilAIisusedup.So ;CItakespartintheprocessionofcorrosionbecauseofthe ;existenceofNaCldeposit.whichresultsinnoprotection ;forAItothematrix,andevendecreasingtheabilityof ;hightemperatureoxideresistanceofthealloy. ;111e

    ;viscosityandcompactiondeceasebecauseofthe ;volatilizationofA1C13andthediffusionandoxidedagain ;ofA1CI3andC12intheoxidedlayer,whichresultingin ;crazingandfallingoffoftheoxidelayer.ThereislittleBi ;solidsoluteinCu,usuallyBidistributetothebordersof ;Cubytheformationofeutectic.Thereisnocorrosive ;outgrowthintheXRDanalysisresults.Anditmaybe ;ascribedtotheprecisionofXRDandtheliRlecontentsof ;Bi.

    ;Theblackregionofthealloyismainly.Cusolid ;solution,A1Cu3,

    ;AhCu9,atomsinthebordersofthetwo

    ;phasesrangenotcontinuous.Therearemanyvacant ;positionsandthecompactionislow,thisprovidesgood ;channelforthediffusionofatomsandmakesC1,O ;diffuseeasilyintothematrixoxideA1.Cu.Sotheblack ;regionoxidizingcorrosionmoreseriouslythanthe ;whiteregionoftheCuBiAIalloy.

    ;Insummary,theCuBiA1alloyhashigh

    ;temperatureoxidedresistance,butwhenthesamplewith ;NaCIdeposit,AIisoxidedfirstlybecausethecorrosion ;ofOandCItakesplaceinrumwhichchangesthe ;mechanismofcorrosion,theoxideforminginthe

    ;surfaceisloose,theeffectofprotectionforthemetal ;decreases,inducingtothecorrosionmoreseriously. ;4.Conclusions

    ;(1)FortheCuBiAIalloywithoutNaC1deposit,a ;compactoxidelayerformsonthesurfaceat700~C- ;900~C,whichhinderscorrosionofthealloyand ;reducestheincreasedweightofcorrosion.Forthe ;34

    ;CuBiAIalloywithNaCIdeposit,theformedoxide ;layerislooseandfallingoffeasily,Theoccurred ;appearanceofpoorAlonthesurfaceofthealloy ;matrixa~achedtotheoxidelayerwillaccelerate ;corrosionbehavior.

    ;(2)WiththeeffectofNaCIdepositathigh

    ;temperature,Alcannotprotectthematrix,even ;decreasinghightemperatureoxideresistanceofthe ;alloy.ThemainlyreasonisthatthecorrosionofOand ;Cltakesplaceinturn.Thepresentworkshowsthatthe ;CuBiA1alloyisnotsuitableforworkingathigh ;temperaturewithchloride.

    ;References:

    ;1]LINJing,YANYongguiandCHENGuang.zhang.

    ;Studyonmicrobiologicallyinfluencedcorrosionofcopper ;manganesealuminiumalloy.RareMetalMaterialsand ;Engineering,2007,36(3):551554.

    ;[2LUYang,YUANLihuaandLIWen.sheng.Corrosion ;resistanceofCu-14%A1.XA1.bronzealloyin3.5%NaCI ;solution.ChineseJournalofMechanicalEngineering, ;2005,(91:42.45.

    ;[3]HANZhong,JIANGWeimingandLINHaichao.Study

    ;oncorrosionbehaviorofaluminumbronzeinseawater ;Pipelinesystem.JournalofChineseSocietyforCorrosion ;andJPr0tection,2000,2D(6):188192.(inChinese)

    ;[4]YuHui,DONGSa?yingandHuANGGuo.sheng. ;CorrosionbehaviorofAl-bronzein3.5%NaClsolution. ;JournalofChineseSocieforCorrosionandProtection. ;2003,(6):345349.(inChinese)

    ;[5]zHANGZhongli,LIDeyuanandZHANGNannan.High

    ;temperatureoxidationbehaviorofarcsprayedduplex ;aluminumbronzebasedcoatings.Transactions0ftheChina ;WeldingInstitution,2006,27(4):8589.(inChinese)

    ;I6]xuTao,CHANGLiminandLIUJianhua.Corrosion

    ;behaviorofaCuCrNiAlalloyinthepresenceofNaCl ;deposit.RareMetals,2006,231:210.2l5.

    ;17]LIYuanshiandNIUYan.CorrosionbehaviorofpureCr ;andtwoCr-containingalloysbeneathZnCl,andKClZnCI,

    ;deposi~.JournalofChineseSocietvforCorrosionand ;Protection,2002,22(1):27.31.(inChinese) ;I81ZHANGNannan,LIDe.yuanandZHANGZhong.1i. ;Studyonhightemperatureoxidationkineticsofarc ;sprayedduplexaluminumbronzebasedcoatings.Welding

    26. ;Technology,2005,3(6):24

    ;f91GUoGui.fen,MAHai.taoandHANShuang.qi. ;Corrosionof0.2%carbonsteelandaluminized0.2% ;carbonsteelbeneathKCldeposit.Corrosion&Protection. ;2005,2l1:21.24.

    ;(EditedbyMalikandDonna)

    ;

Report this document

For any questions or suggestions please email
cust-service@docsford.com