铬、铜、镍和Ca的低碳钢腐蚀行为合成自来水

JournalofAlloysandCompounds391(2005)162–169EffectsofCr,Cu,NiandCaonthecorrosionbehavioroflowcarbonsteelinsynthetictapwaterYoon-SeokChoi,Jae-JooShim,Jung-GuKim∗DepartmentofAdvancedMaterialsEngineering,SungkyunkwanUniversity,300,Chunchun-Dong,Jangan-Gu,Suwon440-746,SouthKoreaReceived8July2004;accepted23July2004Availableonline11November2004AbstractAqueouscorrosionbehaviorsofthelow-alloysteelswithsmallamountsofCr,Cu,NiandCainsynthetictapwaterwerestudiedbyelectrochemicalcorrosiontests(potentiodynamicpolarizationtests,electrochemicalimpedancespectroscopy(EIS))andanalyticaltechniques(XPS,EPMA).Potentiodynamicpolarizationtestrepresentedthatallcurvesshowedactivecorrosionbehaviorandcorrosionpotentialwasshiftedtonobledirectionandcorrosionratetendedtodecreaseastheresultofalloying.ResultsofEISmeasurementshowedthatthemorethecontentofelement,thelargerthepolarizationresistance.Itcanbeseenthattheseresultswerecausedbytheformationofacoherentprotectivefilm,whichcontainedalloyingelements.Actually,XPSresultsshowedthatCr,Cu,andCaformedprotectivemetaloxideatthesurfaceofrustlayerunderstagnantcondition.TheresultsofEPMAindicatedthatCr,Cu,andCaweredistributeddenselyatinnerlayeroftherustlayer,whileNiwasdistributedatthewholelayerunderflowcondition.Consequently,alloyingelementsimprovedcorrosionresistanceoflowcarbonsteel.Itwasreflectedthatcorrosionratesofallspecimenswerequitelow;especially,Cu-,Ni-,andCa-containingspecimensrevealedthelowestcorrosionrateduetotheformationofinsolublerustlayerattheinitialstageofcorrosion.©2004ElsevierB.V.Allrightsreserved.Keywords:Pipelinesteel;Alloyingelement;Corrosioncharacteristics;Electrochemicalmeasurements1.IntroductionIronandsteelpipeshavebeenusedinwaterdistributionsystemsforoverfivecenturies[1].Althoughtheinternalcor-rosionrateofdrinkingwaterpipesislow,internalcorrosionofdrinkingwaterdistributionsystemsleadstotwomajorproblemsforwaterutilities[2,3].Thefirstisthefailureofthedistributionsystempipes.Thisfailureresultsinwaterleakageandlossofhydrauliccapacitycausedbythebuildupofcorrosionproducts.Thesecondproblemisanunwantedchangeinwaterqualityasthegroundwaterisbeingtrans-portedthroughthedistributionsystem.Theresponseofcor-rodedsteeltochangesinwaterqualityisexpectedtobeastrongfunctionofthephysicochemicalcharacteristicsofthecorrosionscales,andisdifferentfromclassicalelectrochem-icalcorrosionofsteel.∗Correspondingauthor.Tel.:[phone];fax:[phone].E-mailaddress:[e-mail](J.-G.Kim).Forthedecreaseofinternalcorrosionrateindrinkingwa-terdistributionsystems,severalmethodshavebeentriedsuchaslining,cleaning,andsoon[4,5].However,thesemethodsarenotfundamentalsolubleproblembuttemporary.Thus,itisnecessarytodevelopanewpipelinesteeloflowcostandhighcorrosionresistance.Changeofpipematerialisoneway,whichcanreduceinternalcorrosionrate,andthencor-rosionproductscanbedecreasedattheinternalregionofpipes.Itiswellknownthatweatheringsteel,containingsmallamountsofalloyingelementssuchasCr,Cu,Ni,SiandP,hasbeenwidelyusedbecauseofitsexcellentresistancetoatmosphericcorrosion.Thisisduetothedevelopmentofanadherent,protectivelayerformedonthesteel[6–9].Inourpreviouswork,theCrandCucompoundspromotemoreorlessprotectiverustlayersonweatheringsteelinanaqueouscondition,astheydowithanatmosphericcondi-tion[10,11].Accordingly,itcanbeexpectedthatalloyingwithsmallamountofnobleelementssuchasCr,CuandNi0925-8388/$–seefrontmatter©2004ElsevierB.V.Allrightsreserved.doi:10.1016/j.jallcom.2004.07.081Y.-S.Choietal./JournalofAlloysandCompounds391(2005)162–169163Table1ChemicalcompositionsofspecimensSpecimenComposition(wt.%)CSiMnPSCrCuNiCaCarbonsteel0.250––0.0400.040––––Crsteel0.0750.2460.9080.0150.0040.972–––Cr–Cu–Nisteel0.0780.2470.8940.0160.0040.9920.1980.150–Cr–Cu–Ni–Casteel0.0790.2480.9120.0160.0041.000.1960.1500.007providesapossibilityforimprovingcorrosionresistanceindistributionsystem.Theaimofthisinvestigationwastodeterminetheinflu-enceofthealloyingelementsontheinternalcorrosionrateofwaterdistributionsystems.Previousinvestigationshavebeenorientedtowardscoupontestsunderstagnantcondition.However,inthisinvestigationparallelstudiesofcouponsandrotatingelectrodeshavebeencarriedouttoachieveabetterunderstandingoftheruleofthealloyingelementsunderflowcondition.2.Experimental2.1.SpecimenandsolutionpreparationSpecimenswerepreparedbymeltinginavacuuminduc-tionfurnace.Afteraddingtheconstituentelements,thecastslabwasreheatedat1200◦Cfor2handhotrolledinto13mmthickplates.Thechemicalcompositionsofthespecimens(wt.%)usedforexperimentsaregiveninTable1.Eachspecimenwasmountedinacuredepoxyresinforstagnantcondition,whiletherotatingcylinderelectrode(1cmdiameter,1.5cmheight)wasusedforflowcondition.Theoutersurfaceofthecylinderwasexposedinsolution.Topreventtheinitiationofcrevicecorrosionbetweentheepoxyandthespecimen,theepoxy–specimeninterfacewaspainted,leavinganexposedareaof1cm2onthemetalsurface.Be-foreeachtest,theworkingelectrodesurfacewastreatedasfollows:polishedwithsiliconcarbideabrasivepaper(fromgrade220–600),thendegreasedwithacetone,rinsedwithdouble-distilledwater,andfinallyimmerse