1、Designation: B 809 95 (Reapproved 2003)Standard Test Method forPorosity in Metallic Coatings by Humid Sulfur Vapor(“Flowers-of-Sulfur”)1This standard is issued under the fixed designation B 809; the number immediately following the designation indicates the year oforiginal adoption or, in the case o
2、f 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 standard covers equipment and test methods fordetermining the porosity of metallic coati
3、ngs, 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,
4、or 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 lite
5、rature.2,3Guide B 765 is suitable toassist in the selection of porosity tests for electrodeposits andrelated metallic coatings. Other porosity test standards are TestMethods B 735, B 741, B 798, and B 799.1.5 The values stated in SI units are to be regarded as thestandard. The values given in parent
6、heses are 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 limitation
7、s prior to use. For specific hazardsstatements, see Section 8.2. Referenced Documents2.1 ASTM Standards:B 374 Terminology Relating to Electroplating4B 542 Terminology Relating to Electrical Contacts andTheir Use5B 735 Test Method for Porosity in Gold Coatings on MetalSubstrates by Nitric Acid Vapor5
8、B 741 Test Method for Porosity in Gold Coatings on MetalSubstrates by Paper Electrography5B 765 Guide for Selection of Porosity Tests for Electrode-posits and Related Metallic Coatings4B 798 Test Method for Porosity in Gold or PalladiumCoatings on Metal Substrates by Gel-Bulk Electrography5B 799 Tes
9、t Method for Porosity in Gold and PalladiumCoatings by Sulfurous Acid/Sulfur-Dioxide Vapor53. Terminology3.1 DefinitionsMany terms used in this test method aredefined in Terminologies B 374 and B 542.3.2 Definitions of Terms Specific to This Standard:3.2.1 corrosion productsreaction products of the
10、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 on thedrawing
11、s of the parts, or by the provision of suitably markedsamples.3.2.3 metallic coatingsin this test method, include plat-ings, claddings, or other metallic coatings applied to thesubstrate. The coating can comprise a single metallic layer ora combination of metallic layers.3.2.4 porositythe presence o
12、f any discontinuity, crack, orhole in the coating that exposes a different underlying metal(see Guide B 765).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 co
13、rrosion products or tarnish films that 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
14、, but not sulfur dioxide (SO2) or othersulfur oxides). They consist of thin films or spots that do notprotrude significantly from the surface of the metallic coating(in contrast to corrosion products).1This test method is under the jurisdiction of ASTM Committee B08 on Metallicand Inorganic Coatings
15、 and is the direct responsibility of Subcommittee B08.10 onTest Methods.Current edition approved Feb. 10, 2003. Published May 2003. Originallyapproved in 1990. Last previous edition approved in 1995 as B 809 95.2Clarke, M., “Porosity and Porosity Tests,” Properties of Electrodeposits, Sard,Leidheise
16、r, and Ogburn, eds., The Electrochemical Society, 1975, p. 122.3Krumbein, S. J., “Porosity Testing of Contact Platings,” Transactions of theConnectors and Interconnection Technology Symposium, Philadelphia, PA, October1987, p. 47.4Annual Book of ASTM Standards, Vol 02.05.5Annual Book of ASTM Standar
17、ds, Vol 02.04.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.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
18、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 Method4.1 The test specimens are
19、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 copperalloy, such as at the bottom
20、 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.Since the chemistry and properties of
21、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 this test procedure is for determinin
22、gcoating 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 deposition process control.5.2 A par
23、ticular 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 into such top layers.5.3 The hum
24、id 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 such product perfor-mance evaluatio
25、ns, 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 of thecoating. In contrast, in a g
26、ood 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 coating.5.5 The humid sulfur test
27、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 cracks do notpenetrate through the ni
28、ckel 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. If the pores are few innumber o
29、r 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 bare copper alloy areas.5.8 This
30、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 performance and service life must
31、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 any convenient-size vessel ofglas
32、s, acrylic-resin (or of any other material that is not affectedby high humidity or sulfur), such as a glass desiccator of 9 to10 L 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 Fixtu
33、re 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 powder (see 6.3).The samples shall al
34、so 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 than20 % of the vessels cross-sectional area so that air movementwithin the vessel will not be restricted during the test.6.3 Glass DishPe
35、tri 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 temperature of 50 6 2C (122 6 4F).6.5 Temperature
36、 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 3It is preferred thatone eyepiece contain a graduated reticle for measuring thediameter of tarnish sp
37、ots. The reticle shall be calibrated for themagnification at which the microscope is to be used.6.7 Light Source, incandescent or circular fluorescent.6The Hygrodynamics Hygrometer, manufactured by Newport Scientific, Inc.,has been found satisfactory for this purpose.B 809 95 (2003)27. Reagents7.1 P
38、otassium Nitrate (KNO3)American Chemical Soci-ety analyzed reagent grade, or better.7.2 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 a
39、lsoinclude, but not be limited to, procuring and reviewing materialSafety Data Sheets (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 therecommend
40、ations given.9. Procedure9.1 Equilibration of Test VesselFor the initial series oftests, 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
41、.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 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
42、will contain undissolved potassiumnitrate salt. This condition is necessary to achieve 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), a
43、nd set the oven to55C.9.1.3 During equilibration, open desiccator occasionally andstir 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 sulf
44、ur (break up anylarge lumps), and place the dish on supports above thepotassium nitrate 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
45、 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, the apparatus isready for insertion of test samples.NOTE 3The system described in this section may be reused for manysubsequent tests without replacing the chemi
46、cals, and will remain stablefor 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 harden
47、ed 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 condition.9.2 Preparation of Test Samples:9.2.1 Handle samples as little as possible, even prior tocleaning, and only with tweezers, micros
48、cope 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 te
49、st environment. Since the test is specific to theplanted metallic portions of the product, the latter should beseparated from plastic housings, etc., whenever possible, priorto cleaning. Also, nonmetallic materials, such as paper tags,string, tape, etc., shall be removed, but take care to maintainsample identity.9.2.3 Cleaning:9.2.3.1 Inspect the samples under 103 magnification forevidence of particulate matter. If present, such particles should7Fisher catalogue no. S-591 or WWR Scientific catalogue no. JT4088 have beenfound satisfactory for this purpos
