Designation:B984−12StandardSpecificationforElectrodepositedCoatingsofPalladium-CobaltAlloyforEngineeringUse1ThisstandardisissuedunderthefixeddesignationB984;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thisspecificationcoversrequirementsforelectrodepos-itedpalladium-cobaltalloycoatingscontainingapproximately80%ofpalladiumand20%ofcobalt.Compositecoatingsconsistingofpalladium-cobaltwithathingoldoverplateforapplicationsinvolvingelectricalcontactsarealsocovered.Palladiumandpalladium-cobaltremaincompetitivefinishesforhighreliabilityapplications.1.2Properties—Palladiumisthelightestandleastnobleoftheplatinumgroupmetals(1)2.IIthasthedensityof12gmpercubiccentimeter,specificgravityof12.0,thatissubstantiallylowerthanthedensityofgold,19.29gmpercubiccentimeter,specificgravity19.3,andplatinum21.48gmpercubiccentimeter,specificgravity21.5.Thedensityofcobaltontheotherhandisevenlessthanpalladium.Itisonly8.69gmpercubiccentimeter,specificgravity8.7.Thisyieldsagreatervolumeorthicknessofcoatingand,consequently,somesavingofmetalweightandreducedcost.Palladium-cobaltcoatedsurfaceprovidesahardsurfacefinish(ASTME18)thusdecreasingwearandincreasingdurability.Palladium-cobaltcoatedsurfacealsohasverylowcoefficientoffriction0.43comparedtohardgold0.60thusprovidinglowermatingandunmatingforcesforelectricalcontacts(1)2.Palladium-cobalthassmallergrainsize(ASTME112),50–150Angstroms,comparedtoHardGold200–250Angstroms(1)2.5–15nanometer,comparedtohardgold20–25nanometer(1)2.Palladium-cobalthaslowporosity(ASTMB799)0.2porosityindexcomparedtohardgold3.7porosityindex(1)2.Palladium-cobaltcoatedsurfacehashigherductility(ASTMB489)3-7thanthatofhardgold<3(1)2.Thepalladium-cobaltcoatedsurfaceisalsothermallymorestable395°Cthanhardgold150°C,andsilver170°C.ThefollowingTable1comparesthehardn...
