ASTM_B_136_-_84_2013.pdf

Designation:B13684(Reapproved 2013)Endorsed by AmericanElectroplaters SocietyEndorsed by NationalAssociation of Metal FinishersStandard Method forMeasurement of Stain Resistance of Anodic Coatings onAluminum1This standard is issued under the fixed designation B136;the number immediately following the designation 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 agencies of the U.S.Department of Defense.1.Scope1.1 This method is intended to determine whether anodicoxide coatings on aluminum and its alloys,that have under-gone a sealing treatment and contact with an acid solution,arestainproof or nonadsorptive with respect to dyes.1.2 Coatings that have been properly sealed should be proofagainst adsorption of coloring materials and,hence,“nonstain-ing”in many types of service.1.3 This method is applicable to anodic coatings intendedfor applications where they are exposed to the weather,or forprotective purposes in corrosive media,and where resistance tostaining is important.NOTE1Performance in this test is predictive only of susceptibility tostain by dyes.It is not intended to be predictive of other factors in serviceperformance such as pitting or general corrosion.NOTE2For Aluminum Association Class I and II architectural anodiccoatings that are sealed in solutions containing less than 15 ppm silicatesor 3 ppm phosphates,the acid pretreatment may be omitted.1.4 In the case of coatings colored in deep shades,whereestimation of the intensity of any residual dye stain is difficult,interpretation of the test is based on whether or not the originalcolor has been affected by the action of the test.1.5 This method is not applicable to:1.5.1 Chromic acid type anodic coatings.1.5.2 Anodic coatings on aluminum alloys containing morethan 2 mass%Cu or 4.5 mass%Si.1.5.3 Anodic coatings that have been sealed only in dichro-mate solutions.1.5.4 Anodic coatings that have undergone a treatment torender them hydrophobic.1.6 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.7 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of whoever uses this standard to consult andestablish appropriate safety and health practices and deter-mine the applicability of regulatory limitations prior to use.2.Summary of Test Method2.1 The method depends upon the observation that a non-sealed or poorly sealed anodic coating is attacked by acid andeasily colored by dye,while an adequately sealed coating is notappreciably attacked and does not retain any dye stain.2.2 The method comprises contacting the test area of theanodized specimen with nitric acid solution and,after rinsingand drying,applying a special dye solution followed by rinsingand rubbing the test area with pumice powder,drying,andvisual examination of the test area for retention of dye stain.Coatings that exhibit no dye stain or change in color areconsidered to have passed the test.3.Reagents3.1 Purity of ReagentsReagent grade chemicals shall beused in all tests.Unless otherwise indicated,it is intended thatall reagents shall conform to the specifications of the Commit-tee onAnalytical Reagents of theAmerican Chemical Society,2where such specifications are available.Other grades may beused,provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.1This method is under the jurisdiction ofASTM Committee B08 on Metallic andInorganic Coatings and is the direct responsibility of Subcommittee B08.07 onConversion Coatings.Current edition approved May 1,2013.Published May 2013.Originallyapproved in 1940.Last previous edition approved in 2008 as B136 84(2008)1.DOI:10.1520/B0136-84R13.2Reagent Chemicals,American Chemical Society Specifications,AmericanChemical Society,Washington,DC.For suggestions on the testing of reagents notlisted by the American Chemical Society,see Analar Standards for LaboratoryChemicals,BDH Ltd.,Poole,Dorset,U.K.,and the United States Pharmacopeiaand National Formulary,U.S.Pharmacopeial Convention,Inc.(USPC),Rockville,MD.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 3.2 Nitric Acid SolutionPrepare a 40 6 5 mass%solutionof nitric acid(HNO3)in distilled or deionized water.NOTE3A convenient way is to carefully add one volume of 70%HNO3(sp gr 1.41 at 20C)to an equal volume of water,while stirring,observing the normal precautions for handling strong acids.3.3 Special Dye SolutionDissolve 1 g of aluminum blue2LW dye3in 50 mL of distilled or deionized water.The pH ofthe dye test solution shall be adjusted to 5.0 6 0.5 andmaintained at this value with a