ASTM_D_1731_-_09_2014.pdf

Designation:D173109(Reapproved 2014)Standard Practices forPreparation of Hot-Dip Aluminum Surfaces for Painting1This standard is issued under the fixed designation D1731;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.1.Scope1.1 These practices describe procedures for the preparationof hot-dip aluminum surfaces for painting.1.2 This standard may involve hazardous materials,operations,and equipment.This standard does not purport toaddress all of the safety concerns,if any,associated with itsuse.It is the responsibility of the user of this standard toestablish appropriate safety and health practices and deter-mine the applicability of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D609 Practice for Preparation of Cold-Rolled Steel Panelsfor Testing Paint,Varnish,Conversion Coatings,andRelated Coating Products2.2 Military Standards:3MIL-DTL-5541 Chemical Conversion Coatings on Alumi-num and Aluminum AlloysMIL-C-15328 Specification for Acid Wash PrimersMIL-M-10578B Metal Conditioner and Rust Remover(Phosphoric Acid Type)3.Types of Surface Preparations3.1 Two types of surface preparations are covered as fol-lows:3.1.1 Solvent Cleaning,and3.1.2 Chemical Treatments.3.2 These two types cover several methods as described inSection 5.Variations in surface treatment produce end condi-tions which differ and which do not necessarily yield identicalresults when paints are applied.Service conditions will dictatethe type of surface preparation that should be selected.4.Solvent Cleaning4.1 The surfaces may be prepared for painting by any of themethods for solvent cleaning described in 4.2 and 4.3.4.2 Method 1Manual swabbing or dip washing with asolvent such as mineral spirits or high flask solvent naphtha.Itis extremely difficult to produce a clean metal surface by thismethod.Accumulated contaminants in the solvent or on theswab are frequently redeposited on the surface being prepared.4.3 Method 2Solvent spray cleaning in accordance withMethod A,Procedure 1 of Practice D609.4.4 Method 3Vapor degreasing in special equipment inaccordance with the latest revision of Method A,Procedure 2of Practice D609,employing trichlorethylene or perchloreth-ylene vapor.Solvent cleaning does not disturb the natural oxidefilm on the metal and may prove adequate for some applica-tions.5.Chemical Treatment5.1 The surfaces may be prepared for painting by any of themethods for chemical treatment(Note 1)described in 5.2 to5.9:NOTE1Materials and procedures employed in these methods oftreatment are available from a number of sources as proprietary com-pounds or methods.Selection may be made from available sources.Thehexavalent chromium methods given are not recommended as hexavalentchromium is a known carcinogen.5.2 Method1,AlkalineCleanersEtchingalkalinesolutions,such as caustic soda,should be avoided because ofthe possibility of dissolving away the aluminum coatingthereby exposing the base metal.Since inhibited alkalinecleaners do not etch the surface,they can be used to removegrease,oil,and other organic solids from hot dip aluminum.After alkali cleaning,the surface should be thoroughly rinsedwith clean water.Most often alkaline-cleaned surfaces aresubsequently processed by one of the following methods,described in 5.3 5.9.5.3 Method 2,Alcoholic Phosphoric Acid Cleaners Thistreatment involves the use of an aqueous solution of phos-phoric acid with alcohol or other organic solvents,togetherwith wetting agents,emulsifying agents,etc.The solution maybe applied by swabbing or dipping(preferably at a temperatureof 70 to 90F(21 to 32C).The solution should remain on the1These practices are under the jurisdiction ofASTM Committee B08 on Metallicand Inorganic Coatings and is the direct responsibility of Subcommittee B08.07 onConversion Coatings.Current edition approved Nov.1,2014.Published November 2014.Originallyapproved in 1960.Last previous edition approved in 2009 as D1731 09.DOI:10.1520/D1731-09R14.2For 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 Standardization Documents Order Desk,DODSSP,Bldg.4,Section D,700 Robbins Ave.,Philadelphia,PA 19111-5098Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 surface for several minutes,followed by thorough rinsing withclean water.A very thin phosphate film is formed which tendsto protect the metal and promote paint adhesion.NOTE2Materials meeting the requirements of the latest revision ofU.S.Military Specification MIL-M-10578B may be used.5.4 Method 3,Acid Fluoride Deoxidizer This tre