ASTM B765-2003(2018) Standard Guide for Selection of Porosity and Gross Defect Tests for Electrodeposits and Related Metallic Coatings.pdf

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1、Designation: B765 03 (Reapproved 2018)Standard Guide forSelection of Porosity and Gross Defect Tests forElectrodeposits and Related Metallic Coatings1This standard is issued under the fixed designation B765; the number immediately following the designation indicates the year oforiginal adoption or,

2、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 guide describes some of the available standardmethods for the detection, ide

3、ntification, and measurement ofporosity and gross defects in electrodeposited and relatedmetallic coatings and provides some laboratory-type evalua-tions and acceptances. Some applications of the test methodsare tabulated in Table 1 and Table 2.1.2 This guide does not apply to coatings that are prod

4、ucedby thermal spraying, ion bombardment, sputtering, and othersimilar techniques where the coatings are applied in the form ofdiscrete particles impacting on the substrate.1.3 This guide does not apply to beneficial or controlledporosity, such as that present in microdiscontinuous chromiumcoatings.

5、1.4 Porosity test results (including those for gross defects)occur as chemical reaction end products. Some occur in situ,others on paper, or in a gel coating. Observations are made thatare consistent with the test method, the items being tested, andthe requirements of the purchaser. These may be vis

6、ualinspection (unaided eye) or by 10 magnification (micro-scope). Other methods may involve enlarged photographs orphotomicrographs.1.5 The test methods are only summarized. The individualstandards must be referred to for the instructions on how toperform the tests.1.6 The values stated in SI units

7、are to be regarded asstandard. The values given in parentheses are for informationonly.1.7 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, health, and environm

8、ental practices and deter-mine the applicability of regulatory limitations prior to use.1.8 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,

9、 Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2B276 Test Method for Apparent Porosity in Cemented Car-bidesB374 Terminology Relating to ElectroplatingB537 Practice for Rating of Electroplated P

10、anels Subjectedto Atmospheric ExposureB542 Terminology Relating to Electrical Contacts and TheirUseB545 Specification for Electrodeposited Coatings of TinB605 Specification for Electrodeposited Coatings of Tin-Nickel AlloyB650 Specification for Electrodeposited Engineering Chro-mium Coatings on Ferr

11、ous SubstratesB689 Specification for Electroplated Engineering NickelCoatingsB733 Specification for Autocatalytic (Electroless) Nickel-Phosphorus Coatings on MetalB734 Specification for Electrodeposited Copper for Engi-neering UsesB735 Test Method for Porosity in Gold Coatings on MetalSubstrates by

12、Nitric Acid VaporB741 Test Method for Porosity In Gold Coatings On MetalSubstrates By Paper Electrography (Withdrawn 2005)3B798 Test Method for Porosity in Gold or Palladium Coat-ings on Metal Substrates by Gel-Bulk ElectrographyB799 Test Method for Porosity in Gold and PalladiumCoatings by Sulfurou

13、s Acid/Sulfur-Dioxide VaporB809 Test Method for Porosity in Metallic Coatings by1This guide is under the jurisdiction of ASTM Committee B08 on Metallic andInorganic Coatings and is the direct responsibility of Subcommittee B08.10 on TestMethods.Current edition approved Aug. 1, 2018. Published August

14、 2018. Originallyapproved in 1986. Last previous edition approved in 2008 as B765 93 (2013).DOI: 10.1520/B0765-03R18.2For 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

15、 the standards Document Summary page onthe ASTM website.3The 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 StatesThis international standard was developed in ac

16、cordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1Humid Sulfur Vapor (“Flowers-

17、of-Sulfur”)B866 Test Method for Gross Defects and Mechanical Dam-age in Metallic Coatings by Polysulfide ImmersionB877 Test Method for Gross Defects and Mechanical Dam-age in Metallic Coatings by the Phosphomolybdic Acid(PMA) Method3. Terminology3.1 DefinitionsMany terms used in this guide are defin

18、edin Terminology B374 or B542.3.2 Definitions of Terms Specific to This Standard:3.2.1 porosityfor the purpose of this guide, porosity in acoating is defined as any hole, crack, or other defect thatexposes the underlying metal to the environment. Differencesbetween the major types of porosity are de

19、scribed in Section 5.3.2.2 underplatea metallic coating layer between the basismetal and the topmost metallic coating. The thickness of anunderplating is usually greater than 1 m, in contrast to a strikeor flash, which are usually thinner.4. Significance and Use4.1 Porosity tests indicate the comple

20、teness of protection orcoverage offered by the coating. When a given coating isknown to be protective when properly deposited, the porosityserves as a measure of the control of the process. The effects ofsubstrate finish and preparation, plating bath, coating process,and handling, may all affect the

21、 degree of imperfection that ismeasured.NOTE 1The substrate exposed by the pores may be the basis metal, anunderplate, or both.4.2 The tests in this guide involve corrosion reactions inwhich the products delineate pores in coatings. Since thechemistry and properties of these products may not resembl

22、ethose found in service environments, these tests are notrecommended for prediction of product performance unlesscorrelation is first established with service experience.5. Applications5.1 From the viewpoint of both porosity testing and func-tional significance, it is useful to divide porosity into

23、two broadcategories, namely intrinsic porosity and gross defects.4,55.1.1 Intrinsic or normal porosity is due primarily to smalldeviations from ideal plating and surface preparation condi-tions. As such, it will be present to some degree in allcommercial thin platings and will generally follow an in

24、verserelationship with thickness. In addition, scanning electronmicroscope (SEM) studies have shown that the diameter ofsuch pores at the plating surface is of the order of micrometers,so that only small areas of underlying metal are exposed to theenvironment.5.1.2 Gross defects, on the other hand,

25、would result incomparatively large areas of exposed basis metal or underplat-ing. Examples of such defects are mechanical damage to thecoating through mishandling or wear. Gross defects can also befound in undamaged coatings in the form of networks ofmicrocracks and as large as-plated poreswith diam

26、eters anorder of magnitude (or more) greater than intrinsic porosity.Such gross defects indicate such serious deviations fromacceptable coating practice as dirty substrates and contami-nated or out-of-balance baths.5.2 Intrinsic porosity and most types of gross defects are toosmall to be seen except

27、 at magnifications so high that a realisticassessment of the overall coating surface in the functional areasof the part cannot be made. Instead, the presence and severityof the porosity is normally determined by some type ofpore-corrosion test that will magnify the pore sites by produc-ing visible r

28、eaction products in and around the pores or cracks.Tests for gross defects (Section 7), and especially for mechani-cal damage and wear, are designed to be less severe. Such tests,4Baker, R. G., Holden, C. A., and Mendizza, A., Proceedings of the AmericanElectroplaters Society, Vol 50, 1963, p. 61.5K

29、rumbein, S. J., “The ASTM Approach to Porosity Testing,” Proc. 1991International Technical Conf. of the American Electroplaters and Surface FinishersSoc., (SUR/FIN 91), Toronto, 1991, pp. 527536.TABLE 1 Applications of Standard Porosity Tests to Metallic Coatings (Section 6)Substrate MetalAGold Silv

30、er Nickel Tin-Nickel Tin Tin-Lead Copper Palladium ChromiumCopper and CopperAlloys6.1B, 6.2,6.4, 6.56.3A 6.4 6.4 6.4 6.4 . 6.2, 6.3A, 6.4,6.5.Nickel 6.1B, 6.2, 6.5 6.3A . . . . . 6.2, 6.3A, 6.5 .Iron or Steel 6.6 . 6.6 6.3B, 6.6 6.3B, 6.6 6.3B, 6.6 6.6 . 6.6Silver 6.4 . 6.4 6.4 6.4 6.4 . 6.4 .AThe s

31、ubstrate may be the basis metal, an underplate, or both (see Note 1).BThickness restrictions may apply.TABLE 2 Applications of Tests for Gross Defects and Mechanical Damage (Section 7)Substrate MetalAGold Nickel Tin-Nickel Tin Tin-Lead Palladium SilverCopper and CopperAlloys7.3, 7.5 7.3, 7.4 7.3 7.3

32、 7.3 7.3, 7.5 7.5Nickel 7.5 . . . . 7.5 7.5Iron or Steel 7.1 7.1 7.1 7.1 7.1 7.1 .Aluminum . 7.2 . . . . .AThe substrate may be the basis metal, an underplate, or both (see Note 1).B765 03 (2018)2however, may not detect a sizeable portion of the smaller(intrinsic) pores in a coating. On the other ha

33、nd, standard testsfor intrinsic porosity (Section 6) will easily reveal the presenceof gross defects as well.5.3 Porosity tests are generally destructive in nature and aredesigned to assess the quality of the coating process inconjunction with the substrate. Therefore, separate test speci-mens are n

34、ot ordinarily allowed.5.4 In the tests summarized in this guide, chemicals reactwith the exposed substrate through the pore or channel to forma product that is either directly observable or that is madeobservable by subsequent chemical development.5.5 Porosity tests differ from corrosion and aging t

35、ests. Agood porosity test process must clean, depolarize, and activatethe substrate metal exposed by the pore, and attack it suffi-ciently to cause reaction products to fill the pore to the surfaceof the coating.The corrosive reagent ideally does not react withthe coating. Reaction time is limited,

36、particularly with thincoatings, since the corrosive will attack the substrate in alldirections and, in so doing, undermine the coatings so that falseobservations may be made. When the corrosion product issoluble in the reagent, a precipitating indicator is used to formthe reaction product.5.6 The su

37、bstrate exposed by the pores may be the basismetal, an underplate, or both.6. Outlines of Standard Porosity Tests for IntrinsicPorosity (5.1.1)NOTE 2The test methods outlined in this section are only summaries.The specified test standard must be referred to for the instructions on howto perform the

38、tests, as well as for important applications and limitations.6.1 Nitric Acid Vapor Test (Test Method B735):6.1.1 ScopeGold coatings on nickel, copper, and theiralloys, where the gold is at least 0.6 m (24 in.) thick.6.1.2 Summary of Test MethodTest specimens are sus-pended over concentrated nitric a

39、cid in a closed nonreactivevessel for a specified time, usually 0.5 to 2.0 h.After exposure,the specimens are dried in an oven to fix the reaction products.Each reaction product spot indicates a pore in the coating.6.2 Paper Electrography (Test Method B741):6.2.1 ScopeGold and palladium coatings on

40、nickel,copper, or copper alloys that have flat or nearly flat surfaces, or,with appropriate fixtures, gently curved surfaces.6.2.2 Summary of Test MethodElectrolyte-soaked paper ispressed against the specimen at controlled pressure. Current, ata constant controlled dc voltage, is passed from an iner

41、tcathode, through the paper, to the specimen (which is made theanode) for a specified time. Base-metal ions at the pore sitesmigrate to the paper where an indicator reagent converts themto colored products (the pore indications).6.3 Sulfur Dioxide Tests:6.3.1 Scope:6.3.1.1 Variation A (Test Method B

42、799, Sulfurous Acid/Sulfur-Dioxide Vapor) applies to gold, palladium, and silverover nickel, copper, and their alloys.6.3.1.2 Variation B applies to tin and its alloys over iron orsteel (Appendixes of Specification B545 and SpecificationB605).6.3.2 Summary of Test MethodThe test specimens aresuspend

43、ed over sulfur-oxide acidic solutions in a sealed cham-ber. For Variation A (Test Method B799), the solution isconcentrated sulfurous acid. For Variation B it is a 1:4 mixtureof 0.1N sulfuric acid and 0.12N sodium thiosulfate solutions.Each reaction product spot on the surface indicates a pore inthe

44、 coating.6.4 Humid Sulfur Vapor (“Flowers-of-Sulfur”) (TestMethod B809):6.4.1 ScopePrimarily for coatings over silver, copper, orcopper alloys. Coatings may include nickel, gold, palladium,tin, and any other coating that does not significantly tarnish inreduced sulfur atmospheres.6.4.2 Summary of Te

45、st MethodTest specimens are sus-pended in a vented closed container over powdered sulfur atcontrolled humidity and temperature. Black or brown spotsindicate porosity.6.5 Gel Electrography (Test Method B798):6.5.1 ScopeGold and palladium coatings over nickel,copper, or copper alloys.6.5.2 The test sa

46、mple is made the anode in a cell of aspecific geometry, which contains a solid electrolyte consistingof gelatin, conducting salts and an indicator. Application of aconstant dc current causes migration of base-metal ionsthrough the pores to the metallic coating surface where reactionwith the indicato

47、r produces colored reaction products.6.6 Ferroxyl Test (Annexes of Specification B689, Specifi-cation B650, and Specification B734):6.6.1 ScopeMetallic coatings included are those that areresistant to ferricyanide and chloride, but are cathodic to iron,steel, or iron-based alloy substrates. Examples

48、 of such coatingsare gold, tin, nickel, copper, chromium, and their alloys.6.6.2 Summary of Test MethodElectrolyte-wetted, gel-chloride treated paper strips are placed firmly in contact withtest specimen surfaces for a specified time, not to exceed 10min. After the allotted time, the paper strips ar

49、e wetted with aferricyanide indicator solution. Blue spots indicate pores.6.6.3 Alternate methods involve formation of the blue spotsdirectly on the specimen (Specification B733, Test Methods,Ferroxyl Test for Iron Base Substrates).7. Outlines of Porosity Tests for Gross Defects andMechanical Damage (5.1.2)NOTE 3Some of the test methods outlined in this section have beentaken from ASTM specifications for specific metallic coatings. As suchthey are only summaries. ASTM Subcommittee B08.10 is developingcomplete test method documents for some of those procedures.