ASTM_B_984_-_12.pdf

Designation:B98412Standard Specification forElectrodeposited Coatings of Palladium-Cobalt Alloy forEngineering Use1This standard is issued under the fixed designation B984;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This specification covers requirements for electrodepos-ited palladium-cobalt alloy coatings containing approximately80%of palladium and 20%of cobalt.Composite coatingsconsisting of palladium-cobalt with a thin gold overplate forapplications involving electrical contacts are also covered.Palladium and palladium-cobalt remain competitive finishesfor high reliability applications.1.2 PropertiesPalladium is the lightest and least noble ofthe platinum group metals(1)2.IIt has the density of 12 gm percubic centimeter,specific gravity of 12.0,that is substantiallylower than the density of gold,19.29 gm per cubic centimeter,specific gravity 19.3,and platinum 21.48 gm per cubiccentimeter,specific gravity 21.5.The density of cobalt on theother hand is even less than palladium.It is only 8.69 gm percubic centimeter,specific gravity 8.7.This yields a greatervolume or thickness of coating and,consequently,some savingof metal weight and reduced cost.Palladium-cobalt coatedsurface provides a hard surface finish(ASTM E18)thusdecreasing wear and increasing durability.Palladium-cobaltcoated surface also has very low coefficient of friction 0.43compared to hard gold 0.60 thus providing lower mating andunmating forces for electrical contacts(1)2.Palladium-cobalthas smaller grain size(ASTM E112),50 150 Angstroms,compared to Hard Gold 200 250 Angstroms(1)2.5 15nanometer,compared to hard gold 20 25 nanometer(1)2.Palladium-cobalt has low porosity(ASTM B799)0.2 porosityindex compared to hard gold 3.7 porosity index(1)2.Palladium-cobalt coated surface has higher ductility(ASTMB489)3-7 than that of hard gold 3(1)2.The palladium-cobaltcoated surface is also thermally more stable 395C than hardgold 150C,and silver 170C.The following Table 1 comparesthe hardness range of electrodeposited palladium-cobalt withother electrodeposited noble metals and alloys(3,4).2TABLE 1-Hardness of Noble MetalsApproximate Hardness(HK25)Gold50250Palladium75600Platinum150550Palladium-Nickel300650Palladium-Cobalt500650Rhodium7501100Ruthenium60013001.3 UnitsThe values stated in SI units are to be regardedas standard.No other units of measurement are included in thisstandard.1.4 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.Some specifichazards statements are given in Section 7 on Hazards.2.Referenced Documents2.1 ASTM Standards:3B183 Practice for Preparation of Low-Carbon Steel forElectroplatingB242 Guide for Preparation of High-Carbon Steel for Elec-troplatingB254 Practice for Preparation of and Electroplating onStainless SteelB281 Practice for Preparation of Copper and Copper-BaseAlloys for Electroplating and Conversion CoatingsB322 Guide for Cleaning Metals Prior to ElectroplatingB343 Practice for Preparation of Nickel for Electroplatingwith NickelB374 Terminology Relating to ElectroplatingB481 Practice for Preparation of Titanium and TitaniumAlloys for ElectroplatingB482 Practice for Preparation of Tungsten and TungstenAlloys for ElectroplatingB487 Test Method for Measurement of Metal and OxideCoating Thickness by Microscopical Examination ofCross Section1This specification is under the jurisdiction of ASTM Committee B08 onMetallic and Inorganic Coatings and is the direct responsibility of SubcommitteeB08.04 on Precious Metal Coatings.Current edition approved May 1,2012.Published September 2012.DOI:10.1520/B0984-122The boldface numbers in parentheses refer to the list of references at the end ofthis specification.3For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 B488 Specification for Electrodeposited Coatings of Goldfor Engineering UsesB489 Practice for Bend Test for Ductility of Electrodepos-ited and Autocatalytically Deposited Metal Coatings onMetalsB499 Test Method for Measurement of Coating Thicknessesby the Magnetic Method:Nonmagnetic Coatings onMagnetic Basis MetalsB507 Practice for Design of Articles to Be Electroplated onRacksB542 Terminology Relating to Electrical Contacts and TheirUseB558 Practice for Preparation of Nickel Alloys for Electro-platingB567 Test Me