1、Designation: B809 95 (Reapproved 2018)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, health, and environmental practices and deter-mine the applicability of regulatory li
7、mitations prior to use.For specific hazards statements, see Section 8.1.7 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-
8、mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.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 MetalSubst
9、rates 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 Related Metallic CoatingsB798 Test Method for Porosity in Gold or Palladium Coat-ings
10、 on Metal Substrates by Gel-Bulk ElectrographyB799 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 Standar
11、d:3.2.1 corrosion productsreaction products 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. Th
12、e measurement area shall be indicated on 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 combinatio
13、n of metallic layers.1This test method 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 Aug. 1, 2018. Published August 2018. Originallyapproved in 1990. Last previous editi
14、on approved in 2013 as B809 95(2013). DOI:10.1520/B0809-95R18.2Clarke, 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 theConnector
15、s and Interconnection Technology Symposium, 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
16、 onthe ASTM website.5The last approved 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 StatesThis international standard was developed in accordance with internationally recogn
17、ized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.13.2.4 porositythe presence of any discontinuity, crack, orhole in
18、 the coating that exposes a different underlying metal(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
19、 interfere withthe function of the part. For many plated 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 othe
20、rsulfur oxides). They consist of thin films or spots that 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 crack
21、s in the coating or from areas of bare silver,copper, 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
22、 Method4.1 The test specimens are suspended over “flowers-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
23、copperalloy, such as at the bottom of pores. Brown or 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.Sinc
24、e the chemistry and properties of these products may notresemble 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 thi
25、s test procedure is for determiningcoating quality. Porosity 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 de
26、position process control.5.2 Aparticular purpose of the 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
27、 into such top layers.5.3 The humid sulfur vapor test 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 su
28、ch product perfor-mance evaluations, the test should only 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 o
29、f thecoating. In contrast, in a good porosity test procedure 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 c
30、oating.5.5 The humid sulfur test is highly sensitive, 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 crac
31、ks do notpenetrate through the nickel underplate overlaying 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.
32、 If the pores are few innumber or away from the significant 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 b
33、are copper alloy areas.5.8 This test method is destructive 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 pe
34、rformance and service life must be madeby the user of 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 a
35、ny convenient-size vessel of glass,acrylic-resin (or of 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
36、serve as a vent.6.2 Sample Fixture or HoldersSupports 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 powde
37、r (see 6.3).The samples shall also be at least 25 mm from 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 (2018)220 % of the vessels cross-sectional area so that air movementwithin the vessel will not
38、 be restricted during the test.6.3 Glass DishPetri or 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 te
39、mperature of 50 6 2C (122 6 4F).6.5 Temperature and Relative 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 r
40、eticle for measuring thediameter of tarnish spots. The 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
41、 Sulfur, Sublimed (“Flowers-of-Sulfur”) , N.F. or labora-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
42、(MSDS) that meet the minimum require-ments of the U.S. 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 oftest
43、s, the test vessel shall be prepared for equilibration 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 satu
44、rated solution of potassium nitrate,prepared by adding 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
45、 a constant humidityatmosphere above the solution.9.1.2 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
46、 contents.As the temperature in the vessel approaches 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
47、 solution or float the dish directly on thesolution (see 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, a
48、nd therelative humidity is in the 86 to 90 % range, the 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 Scie
49、ntific, Inc.,has been found satisfactory for this purpose.7Fisher catalogue no. S-591 or WWR Scientific catalogue no. JT4088 have beenfound satisfactory for this purpose.FIG. 1 Typical Test Equipment SetupB809 95 (2018)3for up to 6 months as long as the chemicals do not become contaminatedwith corrosion products or dirt. If allowed to cool, the potassium 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
