【英文标准名称】:StandardTestMethodforPorosityinGoldandPalladiumCoatingsbySulfurousAcid/Sulfur-DioxideVapor
【原文标准名称】:用亚硫酸/SO2蒸汽测试金和钯镀层孔隙度的标准试验方法
【标准号】:ASTMB799-1995(2009)
【标准状态】:现行
【国别】:美国
【发布日期】:1995
【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】:goldcoatings;goldplatings;palladiumcoatings;palladiumplatings;platingporosity;porecorrosiontest;porositytesting;sulfurdioxidetest;sulfurousacid/SO2test;Contactsurfaces;Contamination--coatings;Corrosion--electrodeposited
【摘要】:Goldcoatingsareoftenspecifiedforthecontactsofseparableelectricalconnectorsandotherdevices.Electrodepositsaretheformofgoldthatismostusedoncontacts,althoughitisalsoemployedasinlayorcladmetalandasweldmentsonthecontactsurface.Theintrinsicnobilityofgoldenablesittoresisttheformationofinsulatingoxidefilmsthatcouldinterferewithreliablecontactoperation.Palladiumcoatingsaresometimesspecifiedasalternativestogoldonelectricalcontactsandsimilarelectricalcomponentsurfaces,bothaselectrodepositsandasinlayorcladmetal.Thistestmethodisparticularlysuitablefordeterminingporosityinpalladiumcoatings,sincethereactiveatmospherethatisuseddoesnotattackthepalladiumifthespecifiedtestconditionsarefollowed.Incontrast,palladiumcoatingsareattackedbynitricacid(HNO3)andotherstrongoxidizingagents,sothatTestMethodB735cannotbeusedfordeterminingtheporosityinsuchcoatings.Inorderforthesecoatingstofunctionasintended,porosity,cracks,andotherdefectsinthecoatingthatexposebase-metalsubstratesandunderplatesmustbeminimalorabsent,exceptinthosecaseswhereitisfeasibletousethecontactsinstructuresthatshieldthesurfacefromtheenvironmentorwherecorrosioninhibitingsurfacetreatmentsforthedepositareemployed.Thelevelofporosityinthecoatingthatmaybetolerabledependsontheseverityoftheenvironmenttotheunderplateorsubstrate,designfactorsforthecontactdeviceliketheforcewithwhichitismated,circuitparameters,andthereliabilityofcontactoperationthatitisnecessarytomaintain.Also,whenpresent,thelocationofporesonthesurfaceisimportant.Iftheporesarefewinnumberandareoutsideofthezoneofcontactofthematingsurfaces,theirpresencecanoftenbetolerated.Methodsfordeterminingporesonacontactsurfacearemostsuitableiftheyenabletheirpreciselocationandnumberstobedetermined.Contactsurfacesareoftencurvedorirregularinshape,andtestingmethodsshouldbesuitableforthem.Inaddition,theseverityofporosity-determiningtestsmayvaryfromprocedurescapableofdetectingallporositytoproceduresthatdetectonlyhighlyporousconditions.Thepresenttestmethodiscapableofdetectingvirtuallyallporosityorotherdefectsthatcouldparticipateincorrosionreactionswiththesubstrateorunderplate.Thetestisrapid,simple,andinexpensive.Inaddition,itcanbeusedoncontactshavingcomplexgeometrysuchaspin-socketcontacts(althoughwithdeeprecessesitispreferredthatthecontactstructuresbeopenedtopermitreactionofthesulfurdioxidewiththeinteriorsignificantsurfaces).Therelationshipofporositylevelsrevealedbyparticularteststocontactbehaviormustbemadebytheuseroftheseteststhroughpracticalexperienceorbyjudgment.Thus,absenceofporosityinthecoatingmaybearequirementforsomeapplications,whileafewporesinthecontactzonemaybeacceptableforothers.Thistestisconsidereddestructiveinthatitrevealsthepresenceofporositybycontaminatingthesurfacewithcorrosionproductsandbyundercuttingthecoatingatporesitesorattheboundariesoftheunplatedareas.Anypartsexposedtothistestshallnotbeplacedinservice.Thistestisintendedtobeusedforquantitativedescriptionsofporosity(suchasnumberofporesperunitareaorpercontact)onlyoncoatingsthathaveaporedensitysufficientlylowthatthecorrosionsitesarewellseparatedandcanbereadilyresolved.Asageneralguidelinethiscanbeachievedforporedensitiesuptoabout100/cm2.Abovethisvaluethetestsareusefulforthequalitativedetectionandcomparisonsofporosity.Forthesepurposes,themeasurementarea