ASTM B825-2002(2008) 在金属试样上表面薄膜的电量(库仑)减少的标准试验方法

作者:标准资料网 时间:2024-05-28 13:05:09  浏览:8219   来源:标准资料网

【英文标准名称】:StandardTestMethodforCoulometricReductionofSurfaceFilmsonMetallicTestSamples
【原文标准名称】:在金属试样上表面薄膜的电量(库仑)减少的标准试验方法
【标准号】:ASTMB825-2002(2008)
【标准状态】:现行
【国别】:美国
【发布日期】:2002
【实施或试行日期】:
【发布单位】:美国材料与试验协会(US-ASTM)
【起草单位】:B02.11
【标准类型】:(TestMethod)
【标准水平】:()
【中文主题词】:
【英文主题词】:atmosphericcorrosion;atmospherictestevaluation;cathodicreduction;controlcouponevaluation;corrosionfilmanalysis;environmentaltesting;monitoringenvironmentaltests;Corrosion--metals/alloys;Coulometry--metallicmaterials;Cathodicreduction
【摘要】:Thepresenttrendinenvironmentaltestingofmaterialswithelectricallyconductivesurfacesistoproduce,underacceleratedlaboratoryconditions,corrosionandfilm-formingreactionsthataresimilartothosethatcausefailuresinserviceenvironments.Inmanyoftheseproceduresthepartsundertestareexposedfordaysorweekstocontrolledquantitiesofbothwatervaporandpollutantgases,whichmaybepresentinextremelydiluteconcentrations.Note28212;DescriptionsofsuchtestscanbefoundinPracticeB827.Manyoftheseenvironmentaltestmethodsrequiremonitoringoftheconditionswithinthechamberduringthetestinordertoconfirmthattheintendedenvironmentallyrelatedreactionsareactuallytakingplace.Themostcommontypeofmonitorconsistsofcopper,silver,orothermetalliccouponsthatareplacedwithinthetestchamberandthatreactwiththecorrosiveenvironmentinmuchthesamewayasthesignificantsurfacesofthepartsundertest.Inpractice,aminimumnumberofcontrolcouponsareplacedineachspecifiedlocation(seeTestMethodB810)withinthechamberforaspecifiedexposuretime,dependingupontheseverityofthetestenvironment.Attheendofthistimeinterval,themetalsamplesareremovedandanalyzedbythecoulometricreductionprocedure.Othercorrosionfilmevaluationtechniquesformetalliccouponsarealsoavailable.Themostcommonoftheseismassgain,whichisnondestructivetothesurfacefilms,butislimitedtothedeterminationofthetotalamountofadditionalmassacquiredbythemetalasaresultoftheenvironmentalattack.Note38212;Detailedinstructionsforconductingsuchweighings,aswellascouponcleaningandsurfacepreparationprocedures,areincludedaspartofTestMethodB810.Note48212;Somesurfaceanalyticaltechniques(suchasX-raymethods)canprovidenondestructiveidentificationofsomecompoundsinthefilms,butsuchmethods,forexample,X-raydiffraction,canmissamorphouscompoundsandcompoundspresentinquantitieslessthan5%ofthetarnishfilmvolume.Withthecoulometrictechnique,itispossibletoresolvethecomplextotalfilmintoanumberofindividualcomponents(Fig.1)sothatcomparisonscanbemade.Thisresolvingpowerprovidesafingerprintcapabilityforidentifyingsignificantdeviationsfromintendedtestconditions,andacomparisonofthecorrosivecharacteristicsofdifferentenvironmentalchambersandofdifferenttestrunswithinthesamechamber.Thecoulometricreductionprocedurecanalsobeusedintestdevelopmentandintheevaluationoftestsamplesthathavebeenexposedatindustrialorotherapplicationenvironments(6).However,foroutdoorexposures,someconstraintsmayhavetobeputontheamountandtypeofcorrosionproductsallowed,particularlythoseinvolvingmoisturecondensationandthepossiblelossoffilmsduetoflaking(alsosee4.9and8.3.2).Inlaboratoryenvironmentaltesting,thecoulometric-reductionprocedureisofgreatestutilityafterrepeatedcharacterizationsofagivencorrosiveenvironmenthavebeenmadetoestablishacharacteristicreductioncurveforthatenvironment.Thesemultiplerunsshouldcomefromboththeuseofmultiplespecimenswithinagiventestexposureaswellasfromseveralconsecutivetestrunswiththesametestconditions.Thecoulometric-reductionprocedureisdestructiveinthatthetarnishfilmsaretransformedduringtheelectrochemicalreductionprocess.Nondestructiveev.........
【中国标准分类号】:H21
【国际标准分类号】:25_220_01
【页数】:8P.;A4
【正文语种】:英语