1、Designation: B809 95 (Reapproved 2013)Standard Test Method forPorosity in Metallic Coatings by Humid Sulfur Vapor(“Flowers-of-Sulfur”)1This standard is issued under the fixed designation B809; the number immediately following the designation indicates the year oforiginal adoption or, in the case of
2、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 standard covers equipment and test methods fordetermining the porosity of metallic coatings
3、, where the porespenetrate down to a silver, 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 a reduced sulfur atmosphere, such asgold, nickel, tin, tin-lead, and palladium, or
4、their alloys.1.3 This test method is designed to determine whether theporosity level is less than or greater than some value which byexperience is considered by the user to be acceptable for theintended application.1.4 Recent reviews of porosity testing and testing methodscan be found in the literat
5、ure.2,3Guide B765 is suitable toassist in the selection of porosity tests for electrodeposits andrelated metallic coatings. Other porosity test standards are TestMethods B735, B741, B798, and B799.1.5 The values stated in SI units are to be regarded as thestandard. The values given in parentheses ar
6、e for informationonly.1.6 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 the applica-bility of regulatory limitations prior
7、to use. For specific hazardsstatements, see Section 8.2. Referenced Documents2.1 ASTM Standards:4B374 Terminology Relating to ElectroplatingB542 Terminology Relating to Electrical Contacts and TheirUseB735 Test Method for Porosity in Gold Coatings on MetalSubstrates by Nitric Acid VaporB741 Test Met
8、hod for Porosity In Gold Coatings On MetalSubstrates By Paper Electrography (Withdrawn 2005)5B765 Guide for Selection of Porosity and Gross Defect Testsfor Electrodeposits and Related Metallic CoatingsB798 Test Method for Porosity in Gold or Palladium Coat-ings on Metal Substrates by Gel-Bulk Electr
9、ographyB799 Test Method for Porosity in Gold and PalladiumCoatings by Sulfurous Acid/Sulfur-Dioxide Vapor3. Terminology3.1 DefinitionsMany terms used in this test method aredefined in Terminologies B374 and B542.3.2 Definitions of Terms Specific to This Standard:3.2.1 corrosion productsreaction prod
10、ucts of the basismetal or underplate, that protrude from, or are otherwiseattached to, the coating surface after the test exposure.3.2.2 measurement areain this test method, that portion orportions of the surface that is examined for the presence ofporosity. The measurement area shall be indicated o
11、n thedrawings of the parts, or by the provision of suitably markedsamples.3.2.3 metallic coatingsin this test method, includeplatings, claddings, or other metallic coatings applied to thesubstrate. The coating can comprise a single metallic layer ora combination of metallic layers.1This test method
12、is under the jurisdiction ofASTM Committee B08 on Metallicand Inorganic Coatings and is the direct responsibility of Subcommittee B08.10 onTest Methods.Current edition approved Dec. 1, 2013. Published December 2013. Originallyapproved in 1990. Last previous edition approved in 2008 as B809 95(2008).
13、 DOI:10.1520/B0809-95R13.2Clarke, M., “Porosity and Porosity Tests,” Properties of Electrodeposits, Sard,Leidheiser, and Ogburn, eds., The Electrochemical Society, 1975, p. 122.3Krumbein, S. J., “Porosity Testing of Contact Platings,” Transactions of theConnectors and Interconnection Technology Symp
14、osium, Philadelphia, PA, October1987, p. 47.4For 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 the standards Document Summary page onthe ASTM website.5The last approve
15、d 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 States13.2.4 porositythe presence of any discontinuity, crack, orhole in the coating that exposes a different underlying metal
16、(see Guide B765).3.2.5 significant surface of a coated part, is that portion(or portions) of the coating surface that is essential to theserviceability or function of the part, or which can be thesource of corrosion products or tarnish films that interfere withthe function of the part. For many plat
17、ed products, the criticalsurface is identical to the measurement area.3.2.6 tarnishreaction products of copper or silver withoxygen or reduced sulfur (that is, hydrogen sulfide (H2S) andelemental sulfur vapor, but not sulfur dioxide (SO2) or othersulfur oxides). They consist of thin films or spots t
18、hat do notprotrude significantly from the surface of the metallic coating(in contrast to corrosion products).3.2.7 tarnish creepagemovement of tarnish films acrossthe surface of the coating, the tarnish having originated eitherfrom pores or cracks in the coating or from areas of bare silver,copper,
19、or copper alloy near the measurement area (as in a cutedge).3.2.8 underplate(s)a metallic coating layer(s) between thesubstrate and the topmost layer or layers. The thickness of anunderplate is usually greater than 1 m (40 in.).4. Summary of Test Method4.1 The test specimens are suspended over “flow
20、ers-of-sulfur” (powdered sulfur) in a vented container at controlledelevated relative humidity and temperature. Elemental sulfurvapor, which always exists in equilibrium with sulfur power ina closed system, attacks any exposed silver, copper, or copperalloy, such as at the bottom of pores. Brown or
21、black tarnishspots indicate porosity.4.2 Exposure periods may vary, depending on the extent ofporosity to be revealed.4.3 This test involves tarnish or oxidation (corrosion) reac-tions in which the products delineate defect sites in coatings.Since the chemistry and properties of these products may n
22、otresemble those found in natural or service environments, thistest is not recommended for prediction of product performanceunless correlation is first established with service experience(but see 5.3).5. Significance and Use5.1 A major use of this test procedure is for determiningcoating quality. Po
23、rosity tests are indications of the complete-ness of protection or coverage offered by the coatings, since thecoatings described in 1.2 are intended to be protective whenproperly applied. The porosity test results are therefore ameasure of the deposition process control.5.2 Aparticular purpose of th
24、e humid sulfur vapor test is fordetermining the quality of underplates of nickel or nickel alloyin those finish systems that have thin, 1.2 m or less (50 in. orless) top layers above the nickel, since porosity in the under-plate usually continues into such top layers.5.3 The humid sulfur vapor test
25、is often used as an envi-ronmental test to simulate many indoor humid atmospheretarnishing and tarnish creepage effects. However, the chemistryand properties of these tarnish films may not resemble thosefound in other service environments. For such product perfor-mance evaluations, the test should o
26、nly be used in combinationwith other performance evaluation tests, as specified in thereferencing document for that product.5.4 Porosity tests differ from corrosion and aging tests, sincethe latter are intended to measure the chemical inertness of thecoating. In contrast, in a good porosity test pro
27、cedure thecorrosive agent should not attack the coating. It must instead,clean, depolarize, or activate the substrate metal exposed by thepore, or both, and attack it sufficiently to cause reactionproducts to fill the pore to the surface of the coating.5.5 The humid sulfur test is highly sensitive,
28、and is capableof detecting virtually all porosity that penetrates down tocopper or copper alloys. Since nickel is not attacked by moistsulfur vapor at 100C or less, this test will not detect pores orcracks in the top coating if such pores or cracks do notpenetrate through the nickel underplate overl
29、aying the copper.5.6 The level of porosity in the coating that may be tolerabledepends on the severity of the environment that the product islikely to encounter during service or storage.Also, the locationof the pores on the surface is important. If the pores are few innumber or away from the signif
30、icant surfaces, their presencecan often be tolerated.5.7 The present test method can be used on samples ofvarious geometries, such as curved surfaces. It can also be usedfor selective area coatings, if allowance is made for tarnishcreepage from bare copper alloy areas.5.8 This test method is destruc
31、tive in that it reveals thepresence of porosity by contaminating the surface with tarnishfilms. Any parts exposed to this test method should not beplaced in service.5.9 The relationship of porosity levels revealed by this testmethod to product performance and service life must be madeby the user of
32、the test through practical experience or byjudgment. Thus, absence of porosity in the coating may be arequirement for some applications, while a few pores on thesignificant surfaces may be acceptable for others.6. Apparatus6.1 Test VesselMay be any convenient-size vessel of glass,acrylic-resin (or o
33、f any other material that is not affected byhigh humidity or sulfur), such as a glass desiccator of 9 to 10L capacity. It should have a lid or cover capable of beingplugged with a stopper. The stopper shall havea1to4mmdiameter hole through it to serve as a vent.6.2 Sample Fixture or HoldersSupports
34、or hangers shallbe made from material such as glass or acrylic plastic that willnot be affected by sulfur or high humidity, and shall bearranged so that the samples will be at least 75 mm away fromthe humidity controlling solution or sulfur powder (see 6.3).The samples shall also be at least 25 mm f
35、rom the vessel wallsand at least 10 mm from other samples or other surfaces. Donot use a desiccator plate. The fixture shall not cover more thanB809 95 (2013)220 % of the vessels cross-sectional area so that air movementwithin the vessel will not be restricted during the test.6.3 Glass DishPetri or
36、other shallow dish approximately15 cm in diameter to hold powdered sulfur. Dish may besupported above the constant humidity solution with plasticblocks, or floated on the liquid.6.4 Oven, Air-circulating, capable of maintaining test vesselat a temperature of 50 6 2C (122 6 4F).6.5 Temperature and Re
37、lative Humidity (RH) Sensor, with aremote sensor probe having a range of approximately 76 to95 % RH at 50C, which can be kept in the desiccator duringtest.66.6 Microscope, Optical, Stereo, 10 It is preferred thatone eyepiece contain a graduated reticle for measuring thediameter of tarnish spots. The
38、 reticle shall be calibrated for themagnification at which the microscope is to be used.6.7 Light Source, incandescent or circular fluorescent.7. Reagents7.1 Potassium Nitrate (KNO3)American Chemical Soci-ety analyzed reagent grade, or better.7.2 Sulfur, Sublimed (“Flowers-of-Sulfur”) , N.F. or labo
39、ra-tory grade.78. Safety and Health Precautions8.1 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 reviewing materialSafety Data Sheets (MSDS) that meet the minimum require-ments of the U.S.
40、 Occupational Safety and Health Administra-tion (OSHA) Hazard Communication Standard for all chemi-cals used in cleaning and testing, and observing therecommendations given.9. Procedure9.1 Equilibration of Test VesselFor the initial series oftests, the test vessel shall be prepared for equilibration
41、 at leasta day before the first exposure.NOTE 1For all subsequent tests, the initial 24-h equilibration proce-dures do not have to be repeated (see Note 2 and 9.8).9.1.1 Place the test vessel in the oven, with sample supportsin place. Make a saturated solution of potassium nitrate,prepared by adding
42、 approximately 200 g of the salt toapproximately 200 mL of deionized water, with stirring, andplace it in the bottom of the vessel.NOTE 2The saturated solution will contain undissolved potassiumnitrate salt. This condition is necessary to achieve a constant humidityatmosphere above the solution.9.1.
43、2 Place lid on the vessel (do not seal it with grease),insert the temperature-humidity probe through the opening inthe top of the lid (leave the stopper out), and set the oven to55C.9.1.3 During equilibration, open desiccator occasionally andstir contents.As the temperature in the vessel approaches
44、50C(122F), as indicated by the temperature probe, adjust oventemperature as needed to stabilize the vessel at 50C.9.1.4 Fill the glass dish half-full with sulfur (break up anylarge lumps), and place the dish on supports above thepotassium nitrate solution or float the dish directly on thesolution (s
45、ee Fig. 1).9.1.5 Replace the lid and insert the vented stopper in the lidopening. Monitor the vessel temperature over several hours,and adjust oven temperature as needed to keep the vessel at 506 2C (122 6 4F). When stability has been attained, and therelative humidity is in the 86 to 90 % range, th
46、e apparatus isready for insertion of test samples.NOTE 3The system described in this section may be reused for manysubsequent tests without replacing the chemicals, and will remain stable6The Hygrodynamics Hygrometer, manufactured by Newport Scientific, Inc.,has been found satisfactory for this purp
47、ose.7Fisher catalogue no. S-591 or WWR Scientific catalogue no. JT4088 have beenfound satisfactory for this purpose.FIG. 1 Typical Test Equipment SetupB809 95 (2013)3for up to 6 months as long as the chemicals do not become contaminatedwith corrosion products or dirt. If allowed to cool, the potassi
48、um nitratemixture will solidify, but it will liquify again when the vessel is reheatedand the solution stirred. Crusts and lumps of hardened potassium nitrateshould be broken up and stirred into the slurry. Add a few millilitres ofdeionized water if necessary to return the solution to its original c
49、ondition.9.2 Preparation of Test Samples:9.2.1 Handle samples as little as possible, even prior tocleaning, and only with tweezers, microscope lens tissue, orclean soft cotton gloves.9.2.2 Prior to being cleaned, the samples shall be preparedso that the measurement areas may be viewed easily throughthe microscope. If samples are part of assembled products, theymay need to be disassembled to ensure proper access to theseareas by the test environment. Since the test is specific to theplanted metallic portions of the product, the latter should besepa
