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【英文标准名称】:StandardTestMethodforGrossDefectsandMechanicalDamageinMetallicCoatingsbythePhosphomolybdicAcid(PMA)Method
【原文标准名称】:磷钼酸(PMA)法检验大的缺陷和机械损伤的标准试验方法
【标准号】:ASTMB877-1996(2008)
【标准状态】:现行
【国别】:美国
【发布日期】:1996
【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】:B08.10
【标准类型】:(TestMethod)
【标准水平】:()
【中文主题词】:
【英文主题词】:electrodeposits;grossdefects;mechanicaldamage;metalliccoatings;porosity;testingfordefects;wearthrough;Damageassessment;Defects--coatings;Electrodepositedcoatings;Goldmetals/alloys;Grossdefects;Mechanicaldamage;Metalliccoatin
【摘要】:TheprimarypurposeofthePMAtestistodeterminethepresenceofmechanicaldamage,wearthrough,andothergrossdefectsinthecoating.Mostmetalliccoatingsareintendedtobeprotective,andthepresenceofgrossdefectsindicatesaseriousreductionofsuchprotection.Theprotectionaffordedbywellappliedcoatingsmaybediminishedbyimproperhandlingfollowingplatingorasaresultofwearormechanicaldamageduringtestingorwhileinservice.ThePMAtestcanservetoindicatetheexistenceofsuchdamage.Thistestisusedtodetectunderplateandsubstratemetalexposedthroughnormalwearduringrelativemotions(matingofelectricalcontacts)orthroughmechanicaldamage.Assuch,itisasensitivepass/failtestand,ifproperlyperformed,willrapidlydetectwearthroughtobasemetalsorscratchesthatenterthebasemetallayers.Thistestisrelativelyinsensitivetosmallpores.Itisnotdesignedtobeageneralporositytestandshallnotbeusedassuch.Thedetectionofporeswilldependupontheirsizesandthelengthoftimethatthereagentremainsaliquid.Thistestcannotdistinguishdegreesofwearthroughorwhetherthewearthroughistonickelorcopper.Oncebasemetalisexposed,thecoloredmolybdenumcomplexisformed.Whilerelativelysmallareadefects(comparedtotheareaofthedroplet)maybeseenatthebottomofthedropastinycoloredregionsimmediatelyafterapplyingthePMA,anylargerareasofexposedbasemetalwillcausetheentiredroplettoturndarkinstantly.ThePMAtestalsodetectsmechanicaldamagethatexposesunderplateandsubstratemetal.Suchdamagemayoccurinanypostplatingoperationorevenattheendoftheplatingoperation.Itcanoftenoccurinassemblyoperationswhereplatedpartsareassembledintolargerunitsbymechanicalequipment.ThePMAtestidentifiesthelocationsofexposedbasemetal.Theextentandlocationoftheseexposedareasmayormaynotbedetrimentaltoperformance.ThePMAtestisnotrecommendedforpredictionsofproductperformance,norisitintendedtosimulatefieldfailuremechanisms.Forsuchcontactperformanceevaluations,anenvironmentaltestknowntosimulateactualfailuremechanismsshouldbeused.ThePMAtestisprimarilyintendedfortheevaluationofindividualsamplesratherthanlargesamplelots,sinceevaluationsarenormallycarriedoutoneatatimeunderthemicroscope(seeSection10).Thistestisdestructive.AnypartsexposedtothePMAtestshallnotbeplacedinservice.1.1Thisteststandardcoversequipmentandmethodsforusingphosphomolybdicacid(PMA)todetectgrossdefectsandmechanicaldamageincludingwearthroughinmetalliccoatingsofgold,silver,orpalladium.Thesemetalscomprisethetopmostmetalliclayersoversubstratesofnickel,copper,orcopperalloys.1.2Recentreviewsofporositytesting,whichincludethoseforgrossdefects,andtestingmethodscanbefoundintheliterature.,AnASTMguidetotheselectionofporosityandgrossdefecttestsforelectrodepositsandrelatedmetalliccoatingsisavailableasGuideB765.OtherrelatedporosityandgrossdefectsteststandardsareTestMethodsB735,B741,B798,B799,B809,andB866,SpecificationsB488,B679,andB689.1.3ThevaluesstatedinSIunitsarethepreferredunits.Thoseinparenthesesareforinformationonly.1.4Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandard......
【中国标准分类号】:J04
【国际标准分类号】:25_220_40
【页数】:5P.;A4
【正文语种】:英语