ASTM B799-1995(2005) Standard Test Method for Porosity in Gold and Palladium Coatings by Sulfurous Acid Sulfur-Dioxide Vapor《用亚硫酸 SO2蒸汽测试金和钯镀层孔隙度的标准试验方法》.pdf
《ASTM B799-1995(2005) Standard Test Method for Porosity in Gold and Palladium Coatings by Sulfurous Acid Sulfur-Dioxide Vapor《用亚硫酸 SO2蒸汽测试金和钯镀层孔隙度的标准试验方法》.pdf》由会员分享,可在线阅读,更多相关《ASTM B799-1995(2005) Standard Test Method for Porosity in Gold and Palladium Coatings by Sulfurous Acid Sulfur-Dioxide Vapor《用亚硫酸 SO2蒸汽测试金和钯镀层孔隙度的标准试验方法》.pdf(4页珍藏版)》请在麦多课文档分享上搜索。
1、Designation: B 799 95 (Reapproved 2005)Standard Test Method forPorosity in Gold and Palladium Coatings by Sulfurous Acid/Sulfur-Dioxide Vapor1This standard is issued under the fixed designation B 799; the number immediately following the designation indicates the year oforiginal adoption or, in the
2、case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers equipment and methods fordetermining the porosity of gold and p
3、alladium coatings,particularly electrodeposits and clad metals used on electricalcontacts.1.2 This 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 Avariety of ot
4、her porosity testing methods are describedin the literature.2,3Other porosity test methods are B 735,B 741, B 798, and B 809. An ASTM Guide to the selection ofporosity tests for electrodeposits and related metallic coatingsis available as Guide B 765.1.4 The values stated in SI units are to be regar
5、ded asstandard. The values given in parentheses are for informationonly.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
6、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 hazards, seeSection 6.2. Referenced Documents2.1 ASTM Standa
7、rds:4B 374 Terminology Relating to ElectroplatingB 542 Terminology Relating to Electrical Contacts andTheir UseB 735 Test Method for Porosity in Gold Coatings on MetalSubstrates by Nitric Acid VaporB 741 Test Method for Porosity In Gold Coatings on MetalSubstrates by Paper Electrography5B 765 Guide
8、for Selection of Porosity and Gross DefectsTests for Electrodeposits and Related Metallic CoatingsB 798 Test Method for Porosity in Gold or PalladiumCoatings on Metal Substrates by Gel-Bulk ElectrographyB 809 Test Method for Porosity in Metallic Coatings ByHumid Sulfur Vapor (“Flowers-of-Sulfur”)3.
9、Terminology3.1 DefinitionsMany terms used in this test method aredefined in Terminology B 542 and terms relating to metalliccoatings are defined in Terminology B 374.3.2 Definitions of Terms Specific to This Standard:3.2.1 corrosion products, nthose reaction products ema-nating from the pores that p
10、rotrude from, or are otherwiseattached to, the coating surface after a vapor test exposure.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 draw
11、ing 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
12、 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.
13、4 porosity, nthe presence of any discontinuity, crack,or hole in the coating that exposes a different underlying metal.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 Me
14、thods.Current edition approved Nov. 1, 2005. Published November 2005. Originallyapproved in 1988. Last previous edition approve in 2000 as B 799 95 (2000).2For example see: Nobel, F. J., Ostrow, B. D., and Thompson, D. W., “ PorosityTesting of Gold Deposits,” Plating, Vol 52, 1965, p. 1001.3S. J. Kr
15、umbien, Porosity Testing of Contact Platings, Proceedings, Connectorsand Interconnection Technology Symposium, Oct. 1987, p 47.4For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information
16、, refer to the standards Document Summary page onthe ASTM website.5Withdrawn.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.5 underplate, na metallic coating layer between thesubstrate and the topmost layer or layers. The thickn
17、ess of anunderplate is usually greater that 0.8 m (30 in.).4. Summary of Test Method4.1 The test method employs concentrated sulfurous acid(H2SO3), which emits sulfur dioxide (SO2) gas according to theequilibrium reaction:H2SO35 SO21 H2O (1)The procedure is similar to one first proposed by Lee andTe
18、rnowski.64.2 Exposure periods may vary, depending upon the degreeof porosity to be revealed. Reaction of the gas with acorrodable base metal at pore sites produces reaction productsthat appear as discrete spots on the gold or palladium surface.Individual spots are counted with the aid of a loupe orl
19、ow-power stereo microscope.4.3 This test method is suitable for coatings containing95 % or more of gold or palladium on substrates of copper,nickel, and their alloys which are commonly used in electricalcontacts.4.4 This porosity test involves corrosion reactions in whichthe products delineate defec
20、t sites in coatings. Since thechemistry and properties of these products may not resemblethose found in natural or service environments this test is notrecommended for prediction of the electrical performance ofcontacts unless correlation is first established with serviceexperience.5. Significance a
21、nd Use5.1 Gold coatings are often specified for the contacts ofseparable electrical connectors and other devices. Electrode-posits are the form of gold that is most used on contacts,although it is also employed as inlay or clad metal and asweldments on the contact surface. The intrinsic nobility of
22、goldenables it to resist the formation of insulating oxide films thatcould interfere with reliable contact operation.5.2 Palladium coatings are sometimes specified as alterna-tives to gold on electrical contacts and similar electricalcomponent surfaces, both as electrodeposits and as inlay orclad me
23、tal. This test method is particularly suitable for deter-mining porosity in palladium coatings, since the reactiveatmosphere that is used does not attack the palladium if thespecified test conditions are followed. In contrast, palladiumcoatings are attacked by nitric acid (HNO3) and other strongoxid
24、izing agents, so that Test Method B 735 cannot be used fordetermining the porosity in such coatings.5.3 In order for these coatings to function as intended,porosity, cracks, and other defects in the coating that exposebase-metal substrates and underplates must be minimal orabsent, except in those ca
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