1、Designation: B 765 03 (Reapproved 2008)Standard 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
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, i
3、dentification, 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 pr
4、oducedby 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 chromiumcoating
5、s.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 v
6、isualinspection (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 uni
7、ts 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 and health practic
8、es and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2B 276 Test Method for Apparent Porosity in CementedCarbidesB 374 Terminology Relating to ElectroplatingB 537 Practice for Rating of Electroplated Panels Subjectedto Atmospheric Expos
9、ureB 542 Terminology Relating to Electrical Contacts andTheir UseB 545 Specification for Electrodeposited Coatings of TinB 605 Specification for Electrodeposited Coatings of Tin-Nickel AlloyB 650 Specification for Electrodeposited Engineering Chro-mium Coatings on Ferrous SubstratesB 689 Specificati
10、on for Electroplated Engineering NickelCoatingsB 733 Specification for Autocatalytic (Electroless) Nickel-Phosphorus Coatings on MetalB 734 Specification for Electrodeposited Copper for Engi-neering UsesB 735 Test Method for Porosity in Gold Coatings on MetalSubstrates by Nitric Acid VaporB 741 Test
11、 Method for Porosity In Gold Coatings On MetalSubstrates By Paper Electrography3B 798 Test Method for Porosity in Gold or PalladiumCoatings on Metal Substrates by Gel-Bulk ElectrographyB 799 Test Method for Porosity in Gold and PalladiumCoatings by Sulfurous Acid/Sulfur-Dioxide VaporB 809 Test Metho
12、d for Porosity in Metallic Coatings byHumid Sulfur Vapor (“Flowers-of-Sulfur”)B 866 Test Method for Gross Defects and MechanicalDamage in Metallic Coatings by Polysulfide ImmersionB 877 Test Method for Gross Defects and Mechanical1This guide is under the jurisdiction of ASTM Committee B08 on Metalli
13、c andInorganic Coatings and is the direct responsibility of Subcommittee B08.10 on TestMethods.Current edition approved Aug. 1, 2008. Published September 2008. Originallyapproved in 1986. Last previous edition approved in 2003 as B 765 93 (2003).2For referenced ASTM standards, visit the ASTM website
14、, 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.3Withdrawn.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, Uni
15、ted States.Damage in Metallic Coatings by the PhosphomolybdicAcid (PMA) Method3. 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:3.2.1 porosityfor the purpose of this guide, porosity in acoating is de
16、fined as any hole, crack, or other 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 i
17、s usually greater than 1 m, in 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 m
18、easure of the control of the process. 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 gui
19、de involve corrosion reactions 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 s
20、ervice experience.5. Applications5.1 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.4,55.1.1 Intrinsic or normal porosity is due primarily to smalldeviations from ideal pl
21、ating and surface preparation 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 surfac
22、e 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, would result incomparatively large areas of exposed basis metal or underplat-ing. Examples of such defects are mechanical damage to thecoating through m
23、ishandling or wear. Gross defects 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
24、 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 at magnifications so high that a realisticassessment of the overall coating surface in the functional areasof the part cannot be made. Instead, the pre
25、sence and severityof the porosity 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
26、be less severe. Such tests,however, 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 a
27、redesigned to assess the quality of the coating process inconjunction with the substrate. Therefore, separate test speci-mens are not ordinarily allowed.4Baker, R. G., Holden, C. A., and Mendizza, A., Proceedings of the AmericanElectroplaters Society, Vol 50, 1963, p. 61.5Krumbein, S. J., “The ASTM
28、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 Silver Nickel Tin-Nickel Tin T
29、in-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 substrate may be the basis
30、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 7.3 7.3, 7.5 7.5Nickel 7.
31、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).B 765 03 (2008)25.4 In the tests summarized in this guide, chemicals reactwith the exposed substrate through the pore or channel to forma product
32、 that is either directly observable or that is madeobservable 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 rea
33、ction products to fill the pore to the surfaceof the coating. The corrosive reagent ideally does not react withthe coating. Reaction time is limited, particularly with thincoatings, since the corrosive will attack the substrate in alldirections and, in so doing, undermine the coatings so that falseo
34、bservations may be made. When the corrosion 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 2T
35、he test methods outlined in this section 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
36、, 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 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 p
37、roducts.Each reaction product spot indicates 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 Tes
38、t MethodElectrolyte-soaked paper ispressed 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
39、 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 799, Sulfurous Acid/Sulfur-Dioxide Vapor) applies to gold, palladium, and silverover nickel, copper, and their alloys.6.3.1.2 Variation B applie
40、s to tin and its alloys over iron orsteel (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. F
41、or 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 coating.6.4 Humid Sulfur Vapor (“Flowers-of-Sulfur”) (TestMethod B 809):6.4.1 ScopePrimarily for coatings over silver, copper, orcopper allo
42、ys. Coatings may include nickel, gold, 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 bro
43、wn spotsindicate porosity.6.5 Gel Electrography (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 in
44、dicator. Application of aconstant dc current 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.
45、1 ScopeMetallic coatings included are those 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
46、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 are wetted with aferricyanide indicator solution. Blue spots indicate pores.6.6.3 Alternate methods involve formation of the blue spotsdir
47、ectly on the specimen (Specification B 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.
48、 As suchthey are only summaries. ASTM Subcommittee 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-based
49、alloy substrates.7.1.2 Summary of Test 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. Afterr
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