ASTM_B_137_-_95_2014.pdf

Designation:B13795(Reapproved 2014)Endorsed by AmericanElectroplaters SocietyEndorsed by NationalAssociation of Metal FinishersStandard Test Method forMeasurement of Coating Mass Per Unit Area on AnodicallyCoated Aluminum1This standard is issued under the fixed designation B137;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 test method covers determination of the mass perunit area of coating on anodically coated aluminum and itsalloys.1.2 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.2.Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent Water3.Significance and Use3.1 This test method is a destructive test procedure suitablefor quality control within manufacturing operations for coatingmass on anodically coated aluminum and aluminum alloys.The mass of the coating is an approximation of its thicknessprovided the conditions under which the coating was applied,or the density of the coating,are known.An anodic coatingsprotective value and amenability to coloring by dying orelectrolytic methods are related to mass of coating per unitarea.4.Reagents4.1 The test solution shall have the following makeup:Chromic acid anhydride(CrO3)20 0.5 gOrthophosphoric acid of 85 mass%,density1.6935 0.5 mLDistilled or deionized water conforming withType III Reagent Water of SpecificationD1193,to make up to1000 mLNOTE1This solution is commonly referred to as a nondestructive“stripping solution”for anodic coatings.This solution dissolves the anodiccoating with no significant attack of the substrate metal.5.Test Specimen5.1 Prepare a test specimen of known surface area,prefer-ably a piece about 75 mm square.If the anodic coating iscontaminated or impregnated with oil,grease,lacquer,etc.,remove as much as possible of this material before determiningthe mass of the coating.It is not usually practicable to removethese materials from the pores of the coating,but surface filmscan frequently be removed by wiping the sample with a clothwet with a suitable solvent.5.2 In cases where it is required to measure the mass ofcoating on only one side of a specimen where both sides haveanodic coatings,the following procedure may be used:5.2.1 Prepare a specimen somewhat larger than required for5.1.5.2.2 Apply a suitable stop off around the edges of thespecimen so that the area on the side of the specimen that is notto be tested is about 75 mm square.Paraffin wax has been usedfor this purpose,but any stop off that resists warm sodiumhydroxide is suitable.5.2.3 Swab the area with a warm solution of sodiumhydroxide(10 mass%,100 g/L)until bare metal is exposed,which is indicated by uniform bubbling over the entire exposedsurface.5.2.4 Swab with warm distilled water.1This test method is under the jurisdiction ofASTM Committee B08 on Metallicand Inorganic Coatingsand is the direct responsibility of Subcommittee B08.07 onConversion Coatings.Current edition approved Nov.1,2014.Published November 2014.Originallyapproved in 1940.Last previous edition approved in 2009 as B137 95(2009).DOI:10.1520/B0137-95R14.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.2.5 Dry with a clean cloth.5.2.6 Swab with diluted nitric acid(1 part HNO3,density1.41,plus 1 part water).5.2.7 Rinse with warm deionized or distilled water.5.2.8 Dry at approximately 100C until dry.5.2.9 Cool and shear off the area covered with stop off,sothat the coated area is the desired size,preferably at least 75mm square.NOTE2The stop off is intended to prevent the coating removalprocess from affecting the test area.Check visually to verify that thesolutions have not run over the edges and removed or damaged the coatedarea to be tested.6.Procedure6.1 Measure the area of the coating.Do not include the areaof cut edges or other uncoated surfaces.6.2 Weigh the test specimen before and after stripping thecoating from it to the nearest 1 mg.6.3 Immerse the test specimen for 5 min in the phosphoric-chromic acid solution maintained at a temperature of about100C.Remove the specimen,wash in distilled or deionizedwater,dry,and weigh.Repeat this cycle of operations until thecoating is completely removed,which is indicated by theweigh