1、Designation: B 866 95 (Reapproved 2003)Standard Test Method forGross Defects and Mechanical Damage in Metallic Coatingsby Polysulfide Immersion1This standard is issued under the fixed designation B 866; the number immediately following the designation indicates the year oforiginal adoption or, in th
2、e 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 fordetecting gross defects and mechanic
3、al 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
4、 solution. 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
5、related metalliccoatings is available as Guide B 765. Other related porosity teststandards are Test Methods B 735, B 741, B 798, B 799, andB 809.1.4 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 pur
6、port 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 the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:B 2
7、46 Specification for Tinned Hard-Drawn and Medium-Hard-Drawn Copper Wire for Electrical Purposes4B 374 Terminology Relating to Electroplating5B 488 Specification for Electrodeposited Coatings of Goldfor Engineering Uses5B 542 Terminology Relating to Electrical Contacts andTheir Use6B 545 Specificati
8、on for Electrodeposited Coatings of Tin5B 605 Specification for Electrodeposited Coatings of Tin-Nickel Alloy5B 679 Specification for Electrodeposited Coatings of Palla-dium for Engineering Use5B 689 Specification for Electrodeposited EngineeringNickel Coatings5B 733 Specification for Autocatalytic
9、(Electroless) Nickel-Phosphorus Coatings on Metal5B 735 Test Method for Porosity in Gold Coatings on MetalSubstrates by Nitric Acid Vapor6B 741 Test Method for Porosity in Gold Coatings on MetalSubstrates by Paper Electrography6B 765 Guide for Selection of Porosity Tests for Electrode-posits and Rel
10、ated Metallic Coatings5B 798 Test Method for Porosity in Gold or PalladiumCoatings on Metal Substrates by Gel-Bulk Electrography6B 799 Test Method for Porosity in Gold and PalladiumCoatings by Sulfurous Acid/Sulfur Dioxide Vapor6B 809 Test Method for Porosity in Metallic Coatings byHumid Sulfur Vapo
11、r (“Flowers-of-Sulfur”)53. Terminology3.1 Definitions: Many terms used in this test method aredefined in Terminologies B 374 or B 542.3.2 Definitions of Terms Specific to This Standard:3.2.1 defect indicationsblack or dark colored productsresulting from the reaction between the alkaline polysulfider
12、eagent and 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 includethose produced by mechanical damage and wear, in addition toas-
13、plated large pores (with diameters an order of magnitudegreater than intrinsic porosity) and networks of microcracks.NOTE 1Such large pores and microcrack networks indicate seriousdeviations from acceptable coating practice (as, for example, dirty1This test method is under the jurisdiction of ASTM C
14、ommittee B08 on Metallicand Inorganic Coatings and is the direct responsibility of Subcommittee B08.10 onTest Methods.Current edition approved Feb. 10, 2003. Published May 2003. Originallyapproved in 1995. Last previous edition approved in 1995 as B 866 95.2Clarke, M., “Porosity and Porosity Tests,”
15、 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. 47.4Annual Book of ASTM Standard
16、s, Vol 02.03.5Annual Book of ASTM Standards, Vol 02.05.6Annual Book of ASTM Standards, Vol 02.04.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.basis-metal substrates and contaminated or out-of-balance plating baths).3.2.3 intrinsic
17、 porositythe “normal” porosity that ispresent, to some degree, in all commercial 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
18、and surface preparation conditions. Scanning electron mi-croscope (SEM) studies 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
19、of thesurface examined for the presence of gross defects or mechani-cal damage (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
20、 basis-metal substrate. The coatingcan comprise a single metallic layer or a combination 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 thebas
21、is metal and the topmost metallic coating. The thickness ofan underplating is usually greater than 1 m, in contrast to astrike or 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
22、tracka mark that indicates the path alongwhich physical contact had been made during 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 dry
23、ing, thesamples are examined for dark or discolored areas whichindicate exposure 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, a
24、nd other gross defects in the coating. Most metalliccoatings are intended to be 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 w
25、ear or mechanical damage during testing or while inservice. The alkaline polysulfide 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
26、specifications for tin-plated coatings, namelySpecifications B 246 and B 545. This test could also be used todetect gross defects and mechanical damage in other metalliccoatings, such as tin-nickel alloy (Specification B 605), nickel(Specification B 689), gold (Specification B 488), palladium(Specif
27、ication B 679), and autocatalytic nickel-phosphorouscoatings (Specification B 733).5.4 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
28、 to occur in productassembly operations.5.5 If properly performed, this test will also 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
29、 of the measurement area cannot be easily made.Other defects, such as many types of wear-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
30、 defects.5.7 The polysulfide solution will react with copper andcopper alloys to produce 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 o
31、r absence ofcopper exposure is a specific requirement.5.8 The polysulfide immersion test is relatively insensitiveto the presence of small pores. It shall not be used as a generalporosity test. (Test Method B 809 should be used instead.)5.9 The extent and location of the gross defects or mechani-cal
32、 damage (revealed by this test) may or may not bedetrimental to product performance or 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 als
33、o be used forselective area coating if allowance is made for tarnish creepagefrom bare 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 servi
34、ce.5.12 However, the defect indications on the sample surfacesthat result from this test 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 perf
35、ormance evaluations, anenvironmental test that is known to simulate actual failuremechanisms should be used.6. 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:
36、6.1.1 MicroscopeOptical, stereo, 10 to 303. It is pre-ferred that one eyepiece contain a graduated reticle for mea-suring the diameter of tarnish spots. The reticle shall becalibrated for the magnification at which the microscope is tobe used, preferably 103.B 866 95 (2003)26.1.2 Hydrometer, 1.120 t
37、o 1.190 specific gravity, 150mmscale.6.1.3 Light Source (Illuminator) for Microscope, incandes-cent, 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, U
38、SP grade.8. Hazards8.1 All of the normal precautions shall be observed inhandling the materials required 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
39、allchemicals used in cleaning and testing, and observing therecommendations given.9. Preparation9.1 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 solu
40、tion of sodium sulfide bydissolving 20 to 25 g of sodium sulfide in 100 mL of deionizedor distilled 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 t
41、he solution is saturated (excesssolids present).9.1.1.2 With stirring, slowly add 30 to 35 g of sulfur 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 gr
42、ade filter paperinto a 250-mL beaker.9.1.1.6 Set aside about 10 mL of filtered solution in a smallstoppered vial. Label the vial, “Concentrated Polysulfide So-lution,” and date it.9.1.1.7 Pour remaining solution into a 250mL graduatedcylinder or hydrometer cylinder. Adjust the specific gravityusing
43、a hydrometer to 1.142 6 0.005, at 20 to 30C, by addinga few millilitres of deionized water and stirring 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 con
44、cen-trated polysulfide solution (see 9.1.1.6) as needed.9.1.1.8 Store solution in a tightly capped 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 cont
45、aining a teflon-coated stirringbar.9.1.2.2 Weigh out 75 g of sodium hydroxide pellets into aplastic 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 mL of deionized water to the beaker, cover,and stir to mix.9.1.2.5
46、 Store solution in a tightly stoppered 500-mL plasticbottle labeled, “Alkaline Polysulfide Reagent,” 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 be
47、ing cleaned, the samples shall be prepared sothat the measurement areas may be viewed easily through 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 soluti
48、on.NOTE 3Since the test is specific to the plated metallic portions of theproduct, the latter should 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 sam
49、ple identity.9.2.3 Cleaning:9.2.3.1 Inspect the samples under 103 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, or other known ozone-destroying compounds.The procedure outlined in Note 4 has been found to givesatisfactory results for coatings with mild to moderate surfacecontamination.NOTE 4Suggested Cleaning Proced
