1、Designation: B 368 09Standard Test Method forCopper-Accelerated Acetic Acid-Salt Spray (Fog) Testing(CASS Test)1This standard is issued under the fixed designation B 368; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of
2、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 Department of Defense.1. Scope1.1 This test method prescribes the condi
3、tions 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 method is applicable to ev
4、aluating 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 correlation of results with s
5、ervice 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 B 537 and E 50, SpecificationsB 456 and B 604, and Test Met
6、hod B 602.1.3 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 to use. For
7、more specificsafety precautionary information see 8.1.2. Referenced Documents2.1 ASTM Standards:2B117 Practice for Operating Salt Spray (Fog) ApparatusB 162 Specification for Nickel Plate, Sheet, and StripB 456 Specification for Electrodeposited Coatings of Cop-per Plus Nickel Plus Chromium and Nick
8、el Plus Chro-miumB 537 Practice for Rating of Electroplated Panels Subjectedto Atmospheric ExposureB 602 Test Method for Attribute Sampling of Metallic andInorganic CoatingsB 604 Specification for Decorative Electroplated Coatingsof Copper Plus Nickel Plus Chromium on PlasticsD 1193 Specification fo
9、r Reagent WaterE50 Practices for Apparatus, Reagents, and Safety Consid-erations for Chemical Analysis of Metals, Ores, andRelated MaterialsE70 Test Method for pH of Aqueous Solutions With theGlass Electrode3. Significance and Use3.1 The CASS test is widely employed and is useful forspecification ac
10、ceptance, simulated service evaluation, manu-facturing control, and research and development. It was devel-oped specifically for use with decorative, electrodepositednickel/chromium and copper/nickel/chromium coatings. Use ofthe test has improved the quality of electroplated parts and ledto the deve
11、lopment 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 supply of compressedair, one or more atomizing nozzles, specimen supports, provi-sion for heating the chamber, and necessary means of
12、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 apparatus is described inthe appendix of Test Method B117. For the CASS test,however, the requirements for air pressure and temperatu
13、re 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).1This test method is under the jurisdiction ofASTM Committee B08 on Metallicand Inorganic Coatings and is the direct responsibility of Subcommit
14、tee B08.10 onTest Methods.Current edition approved April 15, 2009. Published May 2009. Originallyapproved in 1961. Last previous edition approved in 2003 as B 368 97(2003)1.The CASS test was developed by the initiative of the Research Board of theAmerican Electroplaters Society under AES Project 15.
15、2For 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box
16、C700, West Conshohocken, PA 19428-2959, United States.4.3 The apparatus shall be constructed so that drops ofsolution that accumulate on the ceiling or cover of the chamberdo not fall on the specimens being tested. Drops of solutionthat fall from the specimens shall not be returned to thesolution re
17、servoir 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 Solution5.1 Prepare the salt solution by dissolving 5 parts by weightof salt in 95 parts of water conforming to Specification D 1193,Type IV. The salt sh
18、all 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 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 reage
19、nt grade copper chloride (CuCl22H2O) to each liter of the salt solution; dissolve and mixthoroughly.5.3 The pH of the salt-copper solution shall be adjusted tothe 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 equivale
20、nt (Note 3). The pH measurementshall be made electrometrically at 25C. Before the solution isatomized, it shall be free of suspended solids (Note 4).NOTE 2Reference Practice B117and Test Method E70for require-ments on salt. The made up CASS solution should be adjusted to a specificgravity of 1.030 t
21、o 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 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
22、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 of sodium chloride and coppersolution to attain the specified pH, some discrepancy in the system may besuspected (the purity of the water or sal
23、t, or both; the accuracy of the pHmeter; the general cleanliness of the system; etc.).NOTE 4The freshly prepared salt solution may be filtered or decantedbefore 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 cheese
24、cloth 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 oil 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 pass
25、ing 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 filters for compressed air may be used.NOTE 6Atomizing nozzles may have a critical pressure, at which anabnormal increase in the corrosiveness o
26、f 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 MPa by installing a pressureregulator valve minimizes the possibility that the nozzle will be operatedat its critical pressure. Pressure of 0.10
27、 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 the test results, shall bedefined in the specifications covering the material or productbeing tested or shall be mutually agreed upon between the
28、purchaser and the supplier.8. Procedure8.1 Preparation of Test Specimens Clean metallic andmetallic coated specimens. Unless otherwise agreed upon,clean decorative copper/nickel/chromium or nickel/chromiumcoatings immediately before testing by wiping significantsurfaces with a cotton pad saturated w
29、ith 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 the clean surface is free of water break. Anodizedaluminum parts may be cleaned with inhibited 1,1,1-trichloroethane or other suitable organic s
30、olvent (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 chemical cleaning or passivation of stainlesssteel specimens, are permissible when agreed upon betweenthe purchaser and the supplier. Take care
31、 that the specimensafter cleaning are not recontaminated by excessive or carelesshandling. Protect the cut edges of plated, coated, or multilay-ered materials and areas containing identification marks or incontact with the racks or supports with a coating that is stableunder the conditions of the te
32、st, 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 Positioning of SpecimensPosition the specimens inthe CASS test chamber during the test so that the followingconditions are met:8.2.1 Support o
33、r suspend the specimens 15 30 from thevertical and preferably parallel to the principal direction ofhorizontal flow of fog through the chamber, based upon thedominant surface being tested, avoiding pooling of solution onthe sample. See Note 8 on automobile parts.8.2.2 The top of the specimen shall n
34、ot 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 materialcapable 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 solut
35、ion 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 temperature andturning on the air, since storage in an idle chamber overnight,or for other significant length of time, can affect test results.NOTE
36、 7Suitable materials for the construction or coating of racks andsupports are glass, rubber, plastic, or suitably coated wood. Bare metalshould not be used. Specimens are preferably supported from the bottomor the side. Slotted wooden strips are suitable for the support of flat panels.Suspension fro
37、m glass hooks or waxed string may be used as long as theB368092specified position of the specimens is obtained. If necessary, suchsuspension may be made by means of secondary support at the bottom ofthe specimens.NOTE 8Support suspend automobile parts, however, so as to exposeall significant surface
38、s at the general level of the condensate collectors. Ifthe position on the automobile is vertical, place the part in an inclineposition 15-30 from vertical to allow surface wetting by the condensate.If the position on the automobile is facing down, rotate the partapproximately 180 to test the signif
39、icant surface. If there are severalsignificant surfaces at different angles, expose each surface of one or morespecimens.8.3 Conditions in the Salt-Spray ChamberMaintain theexposure zone of the CASS test chamber at a temperature of496 1C during the exposure period (Note 9).The test durationshall com
40、mence when the temperature is 49 6 1C and fog ispresent in the chamber. Heat the air supply by passing finebubbles through heated distilled or deionized water (seeSpecification D 1193, Type IV) so that the temperature of theair after expansion at the nozzle is 49 6 1C. Record thetemperature within t
41、he 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 not inter-rupted for exposing, rearranging, or removing test specimensor to check and replenish the solution in the reservoir).NOTE 9This can be best ac
42、complished by preheating the chamber to49C before starting solution atomization.NOTE 10A suitable method to record the temperature is by athermometer that can be read from outside the closed cabinet. Therecorded temperature must be obtained with the salt-spray chamber closedto avoid a false low read
43、ing, because of wet-bulb effect when the chamberis open.Automatic control of temperature in the chamber and a continuousrecord of temperature are desirable.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
44、 will be collected from the testspecimens or any other source. Position the collectors in eachcorner. The arrangement is shown in Fig. 1. Make sure that 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
45、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 and evapo-ration of condensate should be avoided (Note 14).NOTE 11Suitable collecting devices are glass funnels with the stemsinserted through stoppe
46、rs into graduated cylinders. Funnels with adiameter of 10 cm (area of about 80 cm2) and 50-mL cylinders arepreferred.NOTE 12A solution having a specific gravity of from 1.030 to 1.040,when measured at 25C, will meet the concentration requirement. Theconcentration may also be determined as follows: D
47、ilute 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 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 silvernit
48、rate (AgNO3) (ACS reagent grade) solution to the first appearance of apersistent red coloration. A test solution that requires between 3.9 and 4.9mL of 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
49、 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 specified in thespecification covering the material or product being tested, thetest shall be continuous for the duration of the entire testperiod. Con
