1、Designation: B 765 03Standard Guide forSelection of Porosity and Gross Defect Tests forElectrodeposits and Related Metallic Coatings1This standard is issued under the fixed designation B 765; the number immediately following the designation indicates the year oforiginal adoption or, in the case of r
2、evision, 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 guide describes some of the available standardmethods for the detection, identification, an
3、d 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 producedby thermal
4、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.1.4 Porosity te
5、st 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 visualinspection (
6、unaided eye) or by 103 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 are to be rega
7、rded 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 and health practices and determine
8、the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:B 246 Specification for Tinned Hard-Drawn and Medium-Hard-Drawn Copper Wire for Electrical Purposes2B 276 Test Method for Apparent Porosity in CementedCarbides3B 374 Terminology Relating to Electropla
9、ting3B 537 Practice for Rating of Electroplated Panels Subjectedto Atmospheric Exposure3B 542 Terminology Relating to Electrical Contacts andTheir Use4B 545 Specification for Electrodeposited Coatings of Tin3B 605 Specification for Electrodeposited Coatings of Tin-Nickel Alloy3B 650 Specification fo
10、r Electrodeposited Engineering Chro-mium Coatings on Ferrous Substrates3B 689 Specification for Electroplated Engineering NickelCoatings3B 733 Specification for Autocatalytic (Electroless) Nickel-Phosphorous Coatings on Metal3B 734 Specification for Electrodeposited Copper for Engi-neering Uses3B 73
11、5 Test Method for Porosity in Gold Coatings on MetalSubstrates by Nitric Acid Vapor4B 741 Test Method for Porosity in Gold Coatings on MetalSubstrates by Paper Electrography4B 798 Test Method for Porosity in Gold or PalladiumCoatings on Metal Substrates by Gel-Bulk Electrography4B 799 Test Method fo
12、r Porosity in Gold and PalladiumCoatings by Sulfurous Acid/Sulfur-Dioxide Vapor4B 809 Test Method for Porosity in Metallic Coatings byHumid Sulfur Vapor (Flowers-of-Sulfur)3B 866 Test Method for Gross Defects and MechanicalDamage in Metallic Coatings by Polysulfide Immersion3B 877 Test Method for Gr
13、oss Defects and MechanicalDamage in Metallic Coatings by the PhosphomolybdicAcid (PMA) Method33. Terminology3.1 DefinitionsMany terms used in this guide are definedin Terminology B 374 or B 542.3.2 Definitions of Terms Specific to This Standard:1This guide is under the jurisdiction of ASTM Committee
14、 B08 on Metallic andInorganic Coatings and is the direct responsibility of Subcommittee B08.10 on TestMethods.Current edition approved Sept. 10, 2003. Published Oct. 2003. Originallyapproved in 1986. Last previous edition approved in 2001 as B 765 93 (2001).2Annual Book of ASTM Standards, Vol 02.03.
15、3Annual Book of ASTM Standards, Vol 02.05.4Annual Book of ASTM Standards, Vol 02.04.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.1 porosityfor the purpose of this guide, porosity in acoating is defined as any hole, crack, or o
16、ther defect thatexposes the underlying metal to the environment. Differencesbetween the major types of porosity are described in Section 5.3.2.2 underplatea metallic coating layer between thebasis metal and the topmost metallic coating. The thickness ofan underplating is usually greater than 1 m, in
17、 contrast to astrike or flash, which are usually thinner.4. Significance and Use4.1 Porosity tests indicate the completeness 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 p
18、rocess. The effects ofsubstrate finish and preparation, plating bath, coating process,and handling, may all affect the 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
19、 inwhich the products delineate pores in coatings. Since thechemistry and properties of these products may not resemblethose found in service environments, these tests are notrecommended for prediction of product performance unlesscorrelation is first established with service experience.5. Applicati
20、ons5.1 From the viewpoint of both porosity testing and func-tional significance, it is useful to divide porosity into two broadcategories, namely intrinsic porosity and gross defects.5,65.1.1 Intrinsic or normal porosity is due primarily to smalldeviations from ideal plating and surface preparation
21、condi-tions. As such, it will be present to some degree in allcommercial thin platings and will generally follow an inverserelationship with thickness. In addition, scanning electronmicroscope (SEM) studies have shown that the diameter ofsuch pores at the plating surface is of the order of micromete
22、rs,so that only small areas of underlying metal are exposed to theenvironment.5.1.2 Gross defects, on the other hand, 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 defe
23、cts can also befound in undamaged coatings in the form of networks ofmicrocracks and as large as-plated poreswith diameters anorder of magnitude (or more) greater than intrinsic porosity.Such gross defects indicate such serious deviations fromacceptable coating practice as dirty substrates and conta
24、mi-nated or out-of-balance baths.5.2 Intrinsic porosity and most types of gross defects are toosmall to be seen except 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 poros
25、ity is normally determined by some type ofpore-corrosion test that will magnify the pore sites by produc-ing visible reaction 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,how
26、ever, may not detect a sizeable portion of the smaller(intrinsic) pores in a coating. On the other hand, 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 quali
27、ty of the coating process inconjunction with the substrate. Therefore, separate test speci-mens are not 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 m
28、adeobservable by subsequent chemical development.5.5 Porosity tests differ from corrosion and aging tests. 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
29、 the coating. The corrosive reagent ideally does not react withthe coating. Reaction time is limited, particularly with thin5Baker, R. G., Holden, C. A., and Mendizza, A., Proceedings of the AmericanElectroplaters Society, Vol 50, 1963, p. 61.6Krumbein, S. J., “The ASTM Approach to Porosity Testing,
30、” 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 Silver Nickel Tin-Nickel Tin Tin-Lead Copper Palladium Chro
31、miumCopper 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 substrate may be the basis metal, an underplate, or both
32、 (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 7.3 7.3, 7.5 7.5Nickel 7.5 . . . . 7.5 7.5Iron or Stee
33、l 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).B765032coatings, since the corrosive will attack the substrate in alldirections and, in so doing, undermine the coatings so that falseobservations may be made. When the corro
34、sion product issoluble in the reagent, a precipitating indicator is used to formthe reaction product.5.6 The substrate 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 sectio
35、n are only summaries.The specified test standard must be referred to for the instructions on howto perform the tests, as well as for important applications and limitations.6.1 Nitric Acid Vapor Test (Test Method B 735):6.1.1 ScopeGold coatings on nickel, copper, and theiralloys, where the gold is at
36、 least 0.6 m (24 in.) thick.6.1.2 Summary of Test MethodTest specimens are sus-pended over concentrated nitric acid 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 indi
37、cates a pore in the coating.6.2 Paper Electrography (Test Method B 741):6.2.1 ScopeGold and palladium coatings on nickel, cop-per, 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 ispres
38、sed against the specimen at controlled pressure. Current, ata constant controlled dc voltage, is passed from an inertcathode, 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 th
39、emto colored products (the pore indications).6.3 Sulfur Dioxide Tests:6.3.1 Scope:6.3.1.1 Variation A (Test Method B 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 orste
40、el (Appendixes of Specification B 545 and SpecificationB 605).6.3.2 Summary of Test MethodThe test specimens aresuspended over sulfur-oxide acidic solutions in a sealed cham-ber. For Variation A (Test Method B 799), the solution isconcentrated sulfurous acid. For Variation B it is a 1:4 mixtureof 0.
41、1N sulfuric acid and 0.12N sodium thiosulfate solutions.Each reaction product spot on the surface indicates a pore inthe coating.6.4 Humid Sulfur Vapor (“Flowers-of-Sulfur”) (TestMethod B 809):6.4.1 ScopePrimarily for coatings over silver, copper, orcopper alloys. Coatings may include nickel, gold,
42、palladium,tin, and any other coating that does not significantly tarnish inreduced sulfur atmospheres.6.4.2 Summary of Test 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 Elect
43、rography (Test Method B 798):6.5.1 ScopeGold and palladium coatings over nickel,copper, or copper alloys.6.5.2 The test sample 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 cu
44、rrent causes migration of base-metal ionsthrough the pores to the metallic coating surface where reactionwith the indicator produces colored reaction products.6.6 Ferroxyl Test (Annexes of Specification B 689, Specifi-cation B 650, and Specification B 734):6.6.1 ScopeMetallic coatings included are t
45、hose that areresistant to ferricyanide and chloride, but are cathodic to iron,steel, or iron-based alloy substrates. Examples 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
46、in contact withtest specimen surfaces for a specified time, not to exceed 10min. After the allotted time, the paper strips are wetted with aferricyanide indicator solution. Blue spots indicate pores.6.6.3 Alternate methods involve formation of the blue spotsdirectly on the specimen (Specification B
47、733, 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 S
48、ubcommittee B08.10 is developingcomplete test method documents for some of those procedures.7.1 Hot Water Test (Annex of Specification B 689):7.1.1 ScopeMetallic coatings cathodic to a ferrous sub-strate; for example, nickel, tin, or gold on steel or iron-basedalloy substrates.7.1.2 Summary of Test
49、MethodThe test specimens areimmersed for a specified time in neutral, distilled heated(85C) water that is agitated with clean air. After exposure anddrying, black spots and red rust indicate porosity.7.1.3 Alternative methods involve aerated water at roomtemperature with longer exposure times.7.2 Alizarin Test (Specification B 733, Test Methods, “Po-rosity”):7.2.1 ScopePrimarily for nickel on aluminum substrate.7.2.2 Summary of Test MethodThe surface of the speci-men is swabbed with a sodium hydroxide solution. Afterrinsing, an alizarin sulfonate solution is a
