1、Designation: B368 09 (Reapproved 2014)Standard Test Method forCopper-Accelerated Acetic Acid-Salt Spray (Fog) Testing(CASS Test)1This standard is issued under the fixed designation B368; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisi
2、on, 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.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 This test method
3、 prescribes the conditions required incopper-accelerated acetic acid-salt spray (CASS) testing forspecification purposes. The standard does not specify the typeof test specimen or exposure periods to be used for a specificproduct, nor the interpretation to be given to the results.1.2 This test metho
4、d is applicable to evaluating the corro-sive performance of decorative copper/nickel/chromium ornickel/chromium coatings on steel, zinc alloys, aluminumalloys, and plastics designed for severe service. It is alsoapplicable to the testing of anodized aluminum. The suitabilityof this test and correlat
5、ion of results with service experienceshould be determined before it is specified for coating systemsor materials other than those mentioned in this paragraph.NOTE 1The following standards are not requirements. They arereferenced for information only: Practices B537 and E50, SpecificationsB456 and B
6、604, and Test Method B602.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 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
7、standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For more specificsafety precautionary information see 8.1.2. Referenced Documents2.1 ASTM Standards:2B117 Practice for Operating Salt Spray (Fog) ApparatusB162 Spec
8、ification for Nickel Plate, Sheet, and StripB456 Specification for Electrodeposited Coatings of CopperPlus Nickel Plus Chromium and Nickel Plus ChromiumB537 Practice for Rating of Electroplated Panels Subjectedto Atmospheric ExposureB602 Test Method for Attribute Sampling of Metallic andInorganic Co
9、atingsB604 Specification for Decorative Electroplated Coatings ofCopper Plus Nickel Plus Chromium on PlasticsD1193 Specification for Reagent WaterE50 Practices for Apparatus, Reagents, and Safety Consid-erations for Chemical Analysis of Metals, Ores, andRelated MaterialsE70 Test Method for pH of Aqu
10、eous Solutions With theGlass Electrode3. Significance and Use3.1 The CASS test is widely employed and is useful forspecification acceptance, simulated service evaluation, manu-facturing control, and research and development. It was devel-oped specifically for use with decorative, electrodepositednic
11、kel/chromium and copper/nickel/chromium coatings. Use ofthe test has improved the quality of electroplated parts and ledto the development of new and superior electroplating pro-cesses.4. Apparatus4.1 The apparatus required for the CASS test consists of afog chamber, a salt-solution reservoir, a sup
12、ply of compressedair, one or more atomizing nozzles, specimen supports, provi-sion for heating the chamber, and necessary means of control.4.2 The size and detailed construction of the apparatus areoptional, provided the conditions meet the requirements of thistest method. The construction of the ap
13、paratus is described inthe appendix of Test Method B117. For the CASS test,however, the requirements for air pressure and temperature aretypically 0.08 to 0.12 MPa and 60 to 65C, respectively. Theactual air pressure will be that required to produce the propercollection rate (see 8.3.1).4.3 The appar
14、atus shall be constructed so that drops ofsolution that accumulate on the ceiling or cover of the chamber1This test method is under the jurisdiction ofASTM Committee B08 on Metallicand Inorganic Coatingsand is the direct responsibility of Subcommittee B08.10 onTest Methods.Current edition approved M
15、ay 1, 2014. Published May 2014. Originallyapproved in 1961. Last previous edition approved in 2009 as B368 09. DOI:10.1520/B0368-09R14.The CASS test was developed by the initiative of the Research Board of theAmerican Electroplaters Society under AES Project 15.2For referenced ASTM standards, visit
16、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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959.
17、 United States1do not fall on the specimens being tested. Drops of solutionthat fall from the specimens shall not be returned to thesolution reservoir for respraying.4.4 Materials of construction shall not affect the corrosive-ness of the fog, nor be themselves corroded by the fog.5. Test Solution5.
18、1 Prepare the salt solution by dissolving 5 parts by weightof salt in 95 parts of water conforming to Specification D1193,Type IV. The salt shall be sodium chloride (NaCl),ACS reagentgrade, or equivalent. The pH of this solution shall be between6.0 and 7.0. Impurities or contamination of either the
19、salt or thewater, or both, shall be suspected if the pH is outside of thisrange (Note 2). No adjustment should be made.5.2 Add 0.25 g of reagent grade copper chloride(CuCl22H2O) to each liter of the salt solution; dissolve andmix thoroughly.5.3 The pH of the salt-copper solution shall be adjusted to
20、the range of 3.1 to 3.3, as measured on a sample of thecollected spray, by the addition of glacial acetic acid, ACSreagent grade, or equivalent (Note 3). The pH measurementshall be made electrometrically at 25C. Before the solution isatomized, it shall be free of suspended solids (Note 4).NOTE 2Refe
21、rence Practice B117 and Test Method E70 for require-ments on salt. The made up CASS solution should be adjusted to a specificgravity of 1.030 to 1.040, when measured at a temperature of 25C, willmeet the concentration requirement. It is suggested that a daily check bemade.NOTE 3The initial solution
22、may be adjusted to a pH that gives theproper pH range in the collected solution. Adjustment of the initial pH formakeup solution is based upon the requirements to maintain the requiredpH of the collected samples. If less than 1.3 or more than 1.6 mL of theglacial acetic acid are required per litre o
23、f sodium chloride and coppersolution to attain the specified pH, some discrepancy in the system may besuspected (the purity of the water or salt, or both; the accuracy of the pHmeter; the general cleanliness of the system; etc.).NOTE 4The freshly prepared salt solution may be filtered or decantedbef
24、ore it is placed in the reservoir, or the end of the tube leading from thesolution to the atomizer may be covered with a double layer of cheesecloth to prevent plugging of the nozzle.6. Air Supply6.1 The compressed air supply to the nozzle or nozzles foratomizing the test solution shall be free of o
25、il and dirt (Note 5).Pressure shall be adequate to provide a specified condensaterate.NOTE 5The air supply can be freed of oil and dirt by passing itthrough a water scrubber or at least 60 cm of suitable cleaning material,such as sheeps wool, excelsior, slag wool, or activated alumina. Com-mercial f
26、ilters for compressed air may be used.NOTE 6Atomizing nozzles may have a critical pressure, at which anabnormal increase in the corrosiveness of the salt fog occurs. If the criticalpressure of a nozzle has not been determined with certainty, control offluctuation in the air pressure within 60.0007 M
27、Pa by installing a pressureregulator valve minimizes the possibility that the nozzle will be operatedat its critical pressure. Pressure of 0.10 6 0.02 MPa has been foundsatisfactory.7. Test Specimens7.1 The type and number of test specimens to be used, aswell as the criteria for the evaluation of th
28、e test results, shall bedefined in the specifications covering the material or productbeing tested or shall be mutually agreed upon between thepurchaser and the supplier.8. Procedure8.1 Preparation of Test Specimens Clean metallic andmetallic coated specimens. Unless otherwise agreed upon,clean deco
29、rative copper/nickel/chromium or nickel/chromiumcoatings immediately before testing by wiping significantsurfaces with a cotton pad saturated with a slurry containing 10g of pure magnesium oxide powder (ACS reagent grade) in 100mL of distilled water. Upon rinsing in warm running water, besure that t
30、he clean surface is free of water break. Anodizedaluminum parts may be cleaned with inhibited 1,1,1-trichloroethane or other suitable organic solvent (see Warning).Do not clean organic and other nonmetallic coated specimens.Other methods of cleaning, such as the use of a nitric-acidsolution for the
31、chemical cleaning or passivation of stainlesssteel specimens, are permissible when agreed upon betweenthe purchaser and the supplier. Take care that the specimensafter cleaning are not recontaminated by excessive or carelesshandling. Protect the cut edges of plated, coated, or multilay-ered material
32、s and areas containing identification marks or incontact with the racks or supports with a coating that is stableunder the conditions of the test, such as wax, stop-off lacquer,or pressure-sensitive tape. (Warning1,1,1-Trichloroethaneshould be used in a well-ventilated area away from openflames.)8.2
33、 Positioning of SpecimensPosition the specimens in theCASS test chamber during the test so that the followingconditions are met:8.2.1 Support or suspend the specimens 15 30 from thevertical and preferably parallel to the principal direction ofhorizontal flow of fog through the chamber, based upon th
34、edominant surface being tested, avoiding pooling of solution onthe sample. See Note 8 on automobile parts.8.2.2 The top of the specimen shall not be higher than thetop of the collection tubes.8.2.3 Make sure the specimens do not come in contact witheach other or any other metallic material or any ma
35、terialcapable of acting as a wick.8.2.4 Place each specimen so as to permit free settling of fogon all specimens.8.2.5 Make sure the salt solution from one specimen doesnot drip on any other specimen.8.2.6 Place the specimens in the chamber just prior tobringing the test chamber to the required temp
36、erature andturning on the air, since storage in an idle chamber overnight,or for other significant length of time, can affect test results.NOTE 7Suitable materials for the construction or coating of racks andsupports are glass, rubber, plastic, or suitably coated wood. Bare metalshould not be used.
37、Specimens are preferably supported from the bottomor the side. Slotted wooden strips are suitable for the support of flat panels.Suspension from glass hooks or waxed string may be used as long as thespecified position of the specimens is obtained. If necessary, suchsuspension may be made by means of
38、 secondary support at the bottom ofthe specimens.NOTE 8Support suspend automobile parts, however, so as to exposeall significant surfaces at the general level of the condensate collectors. IfB368 09 (2014)2the position on the automobile is vertical, place the part in an inclineposition 15-30 from ve
39、rtical to allow surface wetting by the condensate.If the position on the automobile is facing down, rotate the partapproximately 180 to test the significant surface. If there are severalsignificant surfaces at different angles, expose each surface of one or morespecimens.8.3 Conditions in the Salt-S
40、pray ChamberMaintain theexposure zone of the CASS test chamber at a temperature of496 1C during the exposure period (Note 9).The test durationshall commence when the temperature is 49 6 1C and fog ispresent in the chamber. Heat the air supply by passing finebubbles through heated distilled or deioni
41、zed water (seeSpecification D1193, Type IV) so that the temperature of theair after expansion at the nozzle is 49 6 1C. Record thetemperature within the exposure zone of the closed cabinet(Note 10) twice a day at least 7 h apart (except Saturdays,Sundays, and holidays, when the salt-spray test is no
42、t inter-rupted for exposing, rearranging, or removing test specimensor to check and replenish the solution in the reservoir).NOTE 9This can be best accomplished by preheating the chamber to49C before starting solution atomization.NOTE 10A suitable method to record the temperature is by athermometer
43、that can be read from outside the closed cabinet. Therecorded temperature must be obtained with the salt-spray chamber closedto avoid a false low reading, because of wet-bulb effect when the chamberis open.Automatic control of temperature in the chamber and a continuousrecord of temperature are desi
44、rable.8.3.1 Place at least two or more (depending on the size ofthe cabinet) clean fog collectors within the exposure zone sothat no drops of solution will be collected from the testspecimens or any other source. Position the collectors in eachcorner. The arrangement is shown in Fig. 1. Make sure th
45、at thefog is such that for each 80 cm2of horizontal collecting areaeach collector collects from 1.0 to 2.0 mL/h of solution, basedon a typical run of at least 22 h (Note 11). Maintain the sodiumchloride concentration of the collected solution between 4.5and 5.5 mass % (Note 12 and Note 13). Dilution
46、 and evapo-ration of condensate should be avoided (Note 14).NOTE 11Suitable collecting devices are glass funnels with the stemsinserted through stoppers into graduated cylinders. Funnels with adiameter of 10 cm (area of about 80 cm2) and 50-mL cylinders arepreferred.NOTE 12A solution having a specif
47、ic gravity of from 1.030 to 1.040,when measured at 25C, will meet the concentration requirement. Theconcentration may also be determined as follows: Dilute 5 mL of thecollected solution to 100 mL with distilled water and mix thoroughly;pipet a 10-mL aliquot into an evaporating dish or casserole; add
48、 40 mL ofdistilled water and 1 mL of 1% potassium chromate (K2CrO4) (ACSreagent grade with less than 0.005% chloride) and titrate with 0.1 N silvernitrate (AgNO3) (ACS reagent grade) solution to the first appearance of apersistent red coloration. A test solution that requires between 3.9 and 4.9mL o
49、f 0.1 N Ag NO3solution will meet the concentration requirements.NOTE 13It has not been found necessary to check copper concentra-tion of the collected solution.NOTE 14Factors that may contribute to dilution and evaporation ofcondensate and make it difficult to control the concentration are lowertemperature, inadequate cover insulation, and prolonged storage of testsolution at above room temperature.8.3.2 Direct or baffle the nozzle or nozzles so that none ofthe spray can impinge directly on the test specimens.8.4 Continuity of TestUnless otherwise s
