ASTM_B_449_-_93_2015.pdf

Designation:B44993(Reapproved 2015)Standard Specification forChromates on Aluminum1This standard is issued under the fixed designation B449;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 specification covers the requirements relating torinsed and nonrinsed chromate conversion coatings on alumi-num and aluminum alloys intended to give protection againstcorrosion and as a base for other coatings.This edition of thespecification has been coordinated with ISO/DIS 10546 and istechnically equivalent.1.2 Aluminum and aluminum alloys are chromate coated inorder to retard corrosion;as a base for organic films includingpaints,plastics,and adhesives;and as a protective coatinghaving a low electrical contact impedance.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 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)ApparatusB602 Test Method for Attribute Sampling of Metallic andInorganic CoatingsB767 Guide for Determining Mass Per Unit Area of Elec-trodeposited and Related Coatings by Gravimetric andOther Chemical Analysis ProceduresD1730 PracticesforPreparationof AluminumandAluminum-Alloy Surfaces for PaintingD3359 Test Methods for Measuring Adhesion by Tape Test2.2 ISO Standards:3ISO 2409 Paint and VarnishesCross-Cut TestISO 3768 Metallic CoatingsNeutral Salt Spray Test(NSSTest)ISO 3892Conversion Coatings on Metallic MaterialsDetermination of Mass Per Unit AreaGravimetricMethodISO 4519 Electrodeposited Metallic Coatings and RelatedFinishesSampling Procedures for Inspection by Attri-butesISO/DIS 10546 Chemical Conversion CoatingsRinsedand Nonrinsed Chromate Conversion CoatingsOn Alu-minum and Aluminum Alloys2.3 Federal Standard:4Fed.Std.No.141 Paints,Varnish,Lacquer,and RelatedMaterials;Methods of Inspection2.4 Military Specification:4MIL-DTL-5541 Chemical Films for Aluminum and Alumi-num Alloys3.Terminology3.1 Definitions:3.1.1 nonrinsedchromate coatings that are dried immedi-ately after the chromating step without receiving a water rinse.3.1.1.1 DiscussionThis special type of coating is typicallyused on long coils of aluminum sheet stock that receive animmediate subsequent paint or adhesive coating.NOTE1Nonrinsed chromate coatings are finding increased usage onfabricated parts and castings.3.1.2 rinsedchromate coatings that are rinsed in waterprior to drying.3.1.2.1 DiscussionThis type of coating is typically appliedto extruded aluminum fabricated parts and castings.4.Classification4.1 Chromate finishes can be applied ranging in color frombrown,thick coatings(Class 1)providing maximum corrosion1This specification is under the jurisdiction of ASTM Committee B08 onMetallic and Inorganic Coatings and is the direct responsibility of SubcommitteeB08.07 on Conversion Coatings.Current edition approved March 1,2015.Published April 2015.Originallyapproved in 1967.Last previous edition approved in 2010 as B449 93(2010)1.DOI:10.1520/B0449-93R15.2For 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.3Available from American National Standards Institute(ANSI),25 W.43rd St.,4th Floor,New York,NY 10036,http:/www.ansi.org.4Available from Standardization Documents Order Desk,DODSSP,Bldg.4,Section D,700 Robbins Ave.,Philadelphia,PA 19111-5098.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 protection to yellow,intermediate thickness coatings(Class 2)suitable as an organic film base or to colorless,thin coatings(Class 3)suitable for low electrical contact resistance.Theyellow coatings vary from golden yellow to iridescent lightyellow.Chromate-phosphate finishes(Class 4)can be appliedranging in color from green to iridescent light green.The Class4 coatings comply with the requirements of MIL-DTL-5541.4.2 Finishers can seldom guarantee to supply exact shadesof color with chromate conversion coatings.If it is necessary tohave exact shades of color,it is possible to dye chromatecoatings having a coating mass greater than 0.4 g/m2to obtaina wide range of colors,but they can only be expected to givean order of added corrosion resistance similar to that providedby the undyed coatin