ASTM_B_798_-_95_2014.pdf

Designation:B79895(Reapproved 2014)Standard Test Method forPorosity in Gold or Palladium Coatings on Metal Substratesby Gel-Bulk Electrography1This standard is issued under the fixed designation B798;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 test method covers equipment and techniques fordetermining porosity in noble metal coatings,particularlyelectrodeposits and clad metals used on electrical contacts.1.2 The test method is designed to show whether theporosity level is less or greater than some value which byexperience is considered by the user to be acceptable for theintended application.1.3 Other porosity testing methods are outlined in GuideB765.Detailed critical reviews of porosity testing are alsoavailable.2Other porosity test methods are B735,B741,B799,and B809.1.4 The values stated in SI units are to be regarded asstandard.The values in parentheses are for information only.1.5 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 become familiarwith all hazards including those identified in the appropriateMaterial Safety Data Sheet(MSDS)for this product/materialas provided by the manufacturer,to establish appropriatesafety and health practices,and determine the applicability ofregulatory limitations prior to use.For specific hazardstatements,see Sections 7 and 8.2.Referenced Documents2.1 ASTM Standards:3B374 Terminology Relating to ElectroplatingB542 Terminology Relating to Electrical Contacts and TheirUseB735 Test Method for Porosity in Gold Coatings on MetalSubstrates by Nitric Acid VaporB741 Test Method for Porosity In Gold Coatings On MetalSubstrates By Paper Electrography(Withdrawn 2005)4B765 Guide for Selection of Porosity and Gross Defect Testsfor Electrodeposits and Related Metallic CoatingsB799 Test Method for Porosity in Gold and PalladiumCoatings by Sulfurous Acid/Sulfur-Dioxide VaporB809 Test Method for Porosity in Metallic Coatings byHumid Sulfur Vapor(“Flowers-of-Sulfur”)3.Terminology3.1 DefinitionsMany terms used in this test method aredefined in Terminology B542 and terms relating to metalliccoatings are defined in Terminology B374.3.2 Definitions of Terms Specific to This Standard:3.2.1 decorations,nthose reaction products emanatingfrom the pores that provide visual contrast with the gelmedium.3.2.2 measurement area(or“significant surface”),nthesurface that is examined for the presence of porosity.Thesignificant surfaces or measurement areas of the part to betested shall be indicated on the drawing of the part or byprovision of suitably marked samples.3.2.2.1 DiscussionFor specification purposes,the signifi-cant surfaces or measurement areas are often defined as thoseportions of the surface that are essential to the serviceability orfunction of the part,such as its contact properties,or which canbe the source of corrosion products or tarnish films thatinterfere with the function of the part.3.2.3 metallic coatings,ninclude platings,claddings,orother metallic layers applied to the substrate.The coatings cancomprise a single metallic layer or a combination of metalliclayers.3.2.4 porosity,nthe presence of any discontinuity,crack,or hole in the coating that exposes a different underlying metal.3.2.5 underplate,na metallic coating layer between thesubstrate and the topmost layer or layers.The thickness of anunderplate is usually greater that 0.8 m(30 in.).1This test method is under the jurisdiction of ASTM Committee B02 onNonferrous Metals and Alloys and is the direct responsibility of SubcommitteeB02.11 on Electrical Contact Test Methods.Current edition approved Oct.1,2014.Published October 2014.Originallyapproved in 1988.Last previous edition approved in 2009 as B798 95(2009).DOI:10.1520/B0798-95R14.2Nobel,F.J.,Ostrow,B.D.,and Thompson,D.W.,“Porosity Testing of GoldDeposity,”Plating,Vol 52,1965,p.1001,and Krumbein S.J.,“Porosity Testing ofContact Platings,”Proceedings,Connectors and Interconnection TechnologySymposium,October 1987,p.47.3For 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.4The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 4.Summary of Test Method4.1 This test method is an electrographic technique,“gel-bulk electrography.”The specimen is made the anode in a cellcontaining a solid or semisolid electrolyte of gelatin,conduct-ing salts,and an indicator.Application of current to this cellresults