1、Designation: B866 95 (Reapproved 2013)Standard Test Method forGross Defects and Mechanical Damage in Metallic Coatingsby Polysulfide Immersion1This standard is issued under the fixed designation B866; 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 () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers equipment and methods fordetecting gross defects and mechanical
3、damage (includingwear-through) in metallic coatings where the breaks in thecoating penetrate down to a copper or copper alloy substrate.1.2 This test method is suitable for coatings consisting ofsingle or combined layers of any coating that does notsignificantly tarnish in an alkaline polysulfide so
4、lution. Ex-amples are gold, nickel, tin, tin-lead, and palladium, or theiralloys.1.3 Recent reviews of porosity testing (which include thosefor gross defects) and testing methods can be found inliterature.2,3An ASTM guide to the selection of porosity andgross defect tests for electrodeposits and rel
5、ated metalliccoatings is available as Guide B765. Other related porosity teststandards are Test Methods B735, B741, B798, B799, andB809.1.4 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.5 This standard does not purport to a
6、ddress 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 the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:4B246 Specif
7、ication for Tinned Hard-Drawn and Medium-Hard-Drawn Copper Wire for Electrical PurposesB374 Terminology Relating to ElectroplatingB488 Specification for Electrodeposited Coatings of Goldfor Engineering UsesB542 Terminology Relating to Electrical Contacts and TheirUseB545 Specification for Electrodep
8、osited Coatings of TinB605 Specification for Electrodeposited Coatings of Tin-Nickel AlloyB679 Specification for Electrodeposited Coatings of Palla-dium for Engineering UseB689 Specification for Electroplated Engineering NickelCoatingsB733 Specification for Autocatalytic (Electroless) Nickel-Phospho
9、rus Coatings on MetalB735 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)5B765 Guide for Selection of Porosity and Gross Defect Testsfor Electrodeposits and Rela
10、ted Metallic CoatingsB798 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 Sulfurous Acid/Sulfur-Dioxide VaporB809 Test Method for Porosity in Metallic Coatings byHumid Sulfur Vapor (“F
11、lowers-of-Sulfur”)3. Terminology3.1 Definitions: Many terms used in this test method aredefined in Terminologies B374 or B542.3.2 Definitions of Terms Specific to This Standard:3.2.1 defect indicationsblack or dark colored productsresulting from the reaction between the alkaline polysulfidereagent a
12、nd exposed copper or copper alloy underlying metal.3.2.2 gross defectsbreaks in the coating that expose rela-tively large areas of underlying metal to the environment(compare with intrinsic porosity (3.2.3). Gross defects include1This test method is under the jurisdiction ofASTM Committee B08 on Met
13、allicand Inorganic Coatings and is the direct responsibility of Subcommittee B08.10 onTest Methods.Current edition approved Dec. 1, 2013. Published December 2013. Originallyapproved in 1995. Last previous edition approved in 2008 as B866 95(2008). DOI:10.1520/B0866-95R13.2Clarke, M., “Porosity and P
14、orosity Tests,” in Properties of Electrodeposits,edited by Sard, Leidheiser, and Ogburn, The Electrochemical Society, 1975, p. 122.3Krumbein, S. J., “Porosity Testing of Contact Platings,” Trans. Connectors andInterconnection Technology Symposium, Philadelphia, PA, October 1987, p. 47.4For reference
15、d 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.5The last approved version of this historical standard is referenced onwww.
16、astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1those produced by mechanical damage and wear, in addition toas-plated large pores (with diameters an order of magnitudegreater than intrinsic porosity) and networks of microcrac
17、ks.NOTE 1Such large pores and microcrack networks indicate seriousdeviations from acceptable coating practice (as, for example, dirtybasis-metal substrates and contaminated or out-of-balance plating baths).3.2.3 intrinsic porositythe “normal” porosity that ispresent, to some degree, in all commercia
18、l thin platings (suchas in precious-metal coatings for engineering purposes) andwill generally follow an inverse relationship with thickness.NOTE 2Intrinsic porosity is due primarily to small deviations fromideal plating and surface preparation conditions. Scanning electron mi-croscope (SEM) studies
19、 have shown that the diameter of such pores, at theplating surface, is of the order of micrometres, so that only small areas ofunderlying metal are exposed to the environment.3.2.4 measurement areathe portion or portions of thesurface examined for the presence of gross defects or mechani-cal damage
20、(and wear-through). The measurement area shall beindicated on the drawings of the parts, or by the provision ofsuitably marked samples.3.2.5 metallic coatingsplatings, claddings, or other metal-lic coatings applied to the basis-metal substrate. The coatingcan comprise a single metallic layer or a co
21、mbination ofmetallic layers.3.2.6 porosity (general)in a coating, the presence of anyhole, crack, or other defect that exposes the underlying metal tothe environment.3.2.7 underplatea metallic coating layer between the basismetal and the topmost metallic coating. The thickness of anunderplating is u
22、sually greater than 1 m, in contrast to a strikeor flash, which is usually thinner.3.2.8 wear-throughthe exposure of underplate or basismetal as a direct result of wear. Wear-through is an observablephenomenon.3.2.9 wear tracka mark that indicates the path alongwhich physical contact had been made d
23、uring a sliding process(such as the mating and unmating of an electrical contact).4. Summary of Test Method4.1 The test samples are immersed in an alkaline polysulfidesolution at 74C (165F) for 60 s. After rinsing and drying, thesamples are examined for dark or discolored areas whichindicate exposur
24、e of copper or copper alloys to the solutionthrough breaks in the coating.5. Significance and Use5.1 The purpose of the alkaline polysulfide immersion test isto determine the presence of mechanical damage, wear-through, and other gross defects in the coating. Most metalliccoatings are intended to be
25、 protective and the presence of grossdefects indicates a serious reduction of such protection.5.2 The protection afforded by well applied coatings may bediminished by improper handling following plating or as aresult of wear or mechanical damage during testing or while inservice. The alkaline polysu
26、lfide test serves to indicate if thedamage has extended down to the copper or copper alloy basismetal since it will not detect exposed nickel underplate.5.3 The alkaline polysulfide test has been specified inseveral ASTM specifications for tin-plated coatings, namelySpecifications B246 and B545. Thi
27、s test could also be used todetect gross defects and mechanical damage in other metalliccoatings, such as tin-nickel alloy (Specification B605), nickel(Specification B689), gold (Specification B488), palladium(Specification B679), and autocatalytic nickel-phosphorouscoatings (Specification B733).5.4
28、 This test detects mechanical damage that exposes cop-per underplate and copper basis metal. Such damage may occurin any post-plating operation or even towards the end of theplating operation. It is most often seen to occur in productassembly operations.5.5 If properly performed, this test will also
29、 detect wear-through, provided the wear-through reaches a copper orcopper-alloy layer.5.6 Many types of gross defects are too small to be seen,except at magnifications so high (as in SEM) that a realisticassessment of the measurement area cannot be easily made.Other defects, such as many types of we
30、ar-through, provideinsufficient contrast with the coating surface. Gross defectstests (as with porosity tests) are, therefore, used to magnify thedefect sites by producing visible reaction products in andaround the defects.5.7 The polysulfide solution will react with copper andcopper alloys to produ
31、ce a dark brown or black stain (the defectindications) at the site of the defect. Silver also turns blackunder the same conditions. The test solution will not react withnickel and is only useful when the presence or absence ofcopper exposure is a specific requirement.5.8 The polysulfide immersion te
32、st is relatively insensitiveto the presence of small pores. It shall not be used as a generalporosity test. (Test Method B809 should be used instead.)5.9 The extent and location of the gross defects or mechani-cal damage (revealed by this test) may or may not bedetrimental to product performance or
33、service life. Suchdeterminations shall be made by the user of the test throughpractical experience or judgment.5.10 The present test can be used on samples of variousgeometries, such as curved surfaces. It can also be used forselective area coating if allowance is made for tarnish creepagefrom bare
34、copper alloy areas.5.11 This test is destructive in that it reveals the presence ofgross defects by contaminating the surface with reaction-product films.Any parts exposed to this test shall not be placedin service.5.12 However, the defect indications on the sample surfacesthat result from this test
35、 are stable; samples may be retained forreference purposes.5.13 This test is neither recommended for predictions ofproduct performance nor is it intended to simulate field failuremechanisms. For such product performance evaluations, anenvironmental test that is known to simulate actual failuremechan
36、isms should be used.B866 95 (2013)26. Apparatus6.1 In addition to the normal equipment (beakers, bottles,weighing balances, funnels, and so forth) that are part of everychemical laboratory, the following apparatus are required:6.1.1 MicroscopeOptical, stereo, 10 to 30. It is preferredthat one eyepie
37、ce contain a graduated reticle for measuring thediameter of tarnish spots. The reticle shall be calibrated for themagnification at which the microscope is to be used, preferably10.6.1.2 Hydrometer, 1.120 to 1.190 specific gravity, 150mmscale.6.1.3 Light Source (Illuminator) for Microscope,incandesce
38、nt, or circular fluorescent.7. Reagents7.1 Sodium Hydroxide, pellet, ACS certified grade or better.7.2 Sodium Sulfide, 9-hydrate, ACS “Analytical Reagent”(AR) grade, or better.7.3 Sulfur, precipitated, USP grade.8. Hazards8.1 All of the normal precautions shall be observed inhandling the materials r
39、equired for this test. This shall alsoinclude, but not be limited to, procuring and reviewingMaterial Safety Data Sheets that meet the minimum require-ments of the OSHA Hazard Communication Standard for allchemicals used in cleaning and testing, and observing therecommendations given.9. Preparation9
40、.1 Preparation of Solutions:9.1.1 Polysulfide SolutionWarningAll work shall bedone under an operating fume hood since the gases emitted andthe polysulfide solution are toxic.9.1.1.1 Make a saturated solution of sodium sulfide bydissolving 20 to 25 g of sodium sulfide in 100 mL of deionizedor distill
41、ed water. Stir for 30 min at minimum. Make sure thatundissolved crystals are present in the solution. If not present,continue adding increments of approximately 0.5g sodiumsulfide, with stirring, until the solution is saturated (excesssolids present).9.1.1.2 With stirring, slowly add 30 to 35 g of s
42、ulfur to thesaturated sodium sulfide solution.9.1.1.3 Cover the beaker. Stir for 60 min at minimum.9.1.1.4 Allow solution to stand for 24 h without stirring.9.1.1.5 Filter solution through qualitative grade filter paperinto a 250-mL beaker.9.1.1.6 Set aside about 10 mL of filtered solution in a smal
43、lstoppered vial. Label the vial, “Concentrated PolysulfideSolution,” and date it.9.1.1.7 Pour remaining solution into a 250mL graduatedcylinder or hydrometer cylinder. Adjust the specific gravityusing a hydrometer to 1.142 6 0.005, at 20 to 30C, by addinga few millilitres of deionized water and stir
44、ring with a glass rodto mix thoroughly. Recheck specific gravity. Continue addingwater and mixing until desired specific gravity is reached. Ifsolution becomes too dilute (less than 1.142), add the concen-trated polysulfide solution (see 9.1.1.6) as needed.9.1.1.8 Store solution in a tightly capped
45、250-mL plasticbottle labeled, “Polysulfide Solution, sp gr 1.142,” and date it.9.1.2 Alkaline Polysulfide Reagent:9.1.2.1 Measure 75 mL of the polysulfide solution, sp gr1.142 into a 600-mL beaker containing a teflon-coated stirringbar.9.1.2.2 Weigh out 75 g of sodium hydroxide pellets into aplastic
46、 weighing dish.9.1.2.3 Add the sodium hydroxide carefully to the polysul-fide solution. Cover beaker. Stir to dissolve.9.1.2.4 Add 375 mLof deionized water to the beaker, cover,and stir to mix.9.1.2.5 Store solution in a tightly stoppered 500-mL plasticbottle labeled, “Alkaline Polysulfide Reagent,”
47、 and date it.9.2 Preparation of Test Samples:9.2.1 Handle samples as little as possible, even beforecleaning, and only with tweezers, microscope-lens tissue, orclean soft cotton gloves.9.2.2 Before being cleaned, the samples shall be prepared sothat the measurement areas may be viewed easily through
48、 themicroscope. If samples are part of assembled products, theymay need to be disassembled to ensure proper access to theseareas and to enable the part to be immersed in the alkalinepolysulfide solution.NOTE 3Since the test is specific to the plated metallic portions of theproduct, the latter should
49、 be separated from plastic housings, etc.,whenever possible, before cleaning. Also, nonmetallic materials, such aspaper tags, string, tape, and so forth, shall be removed, but take care tomaintain sample identity.9.2.3 Cleaning:9.2.3.1 Inspect the samples under 10 magnification forevidence of particulate matter. If present, such particles shouldbe removed by “dusting” (that is, blowing them off the sample)with clean, oil-free air.9.2.3.2 Thoroughly clean the particle-free samples withsolvents or solutions that do not contain CFCs, chlorinatedhydrocarbons, o
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