1、Designation:B20180(Reapproved 2014)Endorsed by AmericanElectroplaters SocietyEndorsed by NationalAssociation of Metal FinishersStandard Practice forTesting Chromate Coatings on Zinc and Cadmium Surfaces1This standard is issued under the fixed designation B201;the number immediately following the des
2、ignation indicates the year oforiginal adoption or,in the case of 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.This standard has been approved for use by agen
3、cies of the U.S.Department of Defense.1.Scope1.1 This practice covers a procedure for evaluating theprotective value of chemical and electrochemical conversioncoatings produced by chromate treatments of zinc and cad-mium surfaces.1.2 The protective value of a chromate coating is usuallydetermined by
4、 salt-spray test and by determining whether ornot the coating possesses adequate abrasion resistance.1.3 Other methods,such as exposure to a humidityenvironment,can be used,but are generally of too long aduration to be of practical value.“Steam Tests”using pressurecookers have also been used for tes
5、ting chromate films onhot-dip galvanized surfaces.1.4 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.5 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility
6、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.2.Referenced Documents2.1 ASTM Standards:2B117 Practice for Operating Salt Spray(Fog)Apparatus3.Terminology3.1 Definitions of Terms Specific to T
7、his Standard:3.1.1 time to failuretime to failure will depend on the typeof coating tested.A list of some expected protective valuesobtainable in a given salt spray test is shown in Appendix X2.3.1.1.1 DiscussionIn most instances,failure is defined asthe first appearance on significant surfaces of w
8、hite corrosionproducts visible to the unaided eye at normal reading distance,except that the presence of white corrosion products at sharpedges(for example,on threaded fasteners)and at junctionsbetween dissimilar metals should not be considered failure.Insome instances,it may be desirable to regard
9、the first appear-ance of red rust as failure.3.1.2 significant surfacesin general,significant surfacesare those surfaces that are visible and subject to corrosion orwear,or both,except that surfaces that are normally difficult tocoat by electroplating or mechanical deposition may be ex-empt.The desi
10、gnation of significant surfaces may be indicatedon the drawing.4.Significance and Use4.1 This practice is applicable to chromate coatings of thecolorless(both one and two-dip),iridescent yellow or bronze,olive drab,black,colorless anodic,yellow or black anodictypes,and of the dyed variety,when appli
11、ed to surfaces ofelectrodeposited zinc,mechanically deposited zinc,hot-dippedzinc,rolled zinc,electrodeposited cadmium,mechanicallydeposited cadmium,and zinc die castings.NOTE1Colorless coatings are also referred to as clear-bright orblue-bright coatings.4.2 Because of variables inherent in the salt
12、-spray test,which may differ from one test cabinet to another,interpreta-tion of test results for compliance with expected performanceshould be specified by the purchaser.1This practice is under the jurisdiction of ASTM Committee B08 on Metallicand Inorganic Coatings and is the direct responsibility
13、 of Subcommittee B08.07 onConversion Coatings.Current edition approved Nov.1,2014.Published November 2014.Originallyapproved in 1945.Last previous edition approved in 2009 as B201 80(2009)1.DOI:10.1520/B0201-80R14.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Cust
14、omer 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.United States1 4.3 Properties such as thickness,color,lus
15、ter,and ability toprovide good paint adhesion are not covered in this practice,nor are the chemical composition and the method of applica-tion of these finishes.5.Conditioning5.1 AgingBefore subjecting a chromate coating to test,itmust be aged at room temperature in a clean environment forat least 2
16、4 h after the chromating treatment.5.2 Preparation of SpecimenThe test surface must be freeof fingerprints and other extraneous stains and must not becleaned except by gentle wiping with a clean,dry,soft cloth toremove loose particles.Oily or greasy surfaces should not beused for testing,and degreasing with organic solvents is notrecommended.6.Procedure6.1 Salt Spray TestExpose the clean specimen to a 5%solution salt spray and conduct the test in accordance with thelatest revision of Practice B1
