1、Designation:D267472(Reapproved 2021)Standard Methods ofAnalysis of Sulfochromate Etch Solution Used in SurfacePreparation of Aluminum1This standard is issued under the fixed designation D2674;the number immediately following the designation indicates the year oforiginal adoption or,in the case of re
2、vision,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 methods offer a means for controlling the effec-tiveness of the etchant which is normally used for
3、 preparing thesurface of aluminum alloys for subsequent adhesive bonding.As the etchant reacts with the aluminum,hexavalent chromiumis converted to trivalent chromium;a measure of the two andthe difference can be used to determine the amount of dichro-mate used.1.2 The sulfochromate solution can be
4、replenished by re-storing the sodium dichromate and the sulfuric acid to theoriginal formulation levels.The lower limit of usefulness willvary depending upon solution storage,adhesives used,criticalnature of bond capability,variety of metals processed,etc.andshould be determined.Replenishment will b
5、e limited to thenumber of times the chemical ingredients can be restored andmaintained to the required levels and should be determined bythe user.Sludge collecting in the bottom of a tank should beminimized by periodic removal of sludge.For someapplications,the hexavalent chromium should not fall be
6、lowthe trivalent chromium content.1.3 A typical aqueous sulfochromate acid etch solutionformulation is as follows:Sodium dichromate(Na2Cr2O7)4.5 oz/gal(33.7 g/litre)Sulfuric acid(sp gr 1.84)45 oz/gal(337.1 g/litre)1.4 Maintenance of the aqueous concentrations is suggestedas follows by appropriate ad
7、ditions of sodium dichromate orsulfuric acids.Sodium dichromate3.0 to 6.0 oz/gal(22.5 to 44.9 g/litre)Sulfuric acid40 to 50 oz/gal(299.6 to 374.5 g/litre)1.5 Method A is intended for measuring the sulfuric acidcontent of a sulfochromate solution.Method B is intended formeasuring the hexavalent and t
8、rivalent Chromium content of asulfochromate solution.Method C is intended as an alternativemethod for measuring the hexavalent and trivalent Chromiumcontent of a sulfochromate solution.1.6 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theres
9、ponsibility of the user of this standard to establish appro-priate safety,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.7 This international standard was developed in accor-dance with internationally recognized principles on standard-iza
10、tion established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterE50 Practices for Ap
11、paratus,Reagents,and Safety Consid-erations for Chemical Analysis of Metals,Ores,andRelated Materials3.Purity of Reagents and Water3.1 Purity of ReagentsReagent grade chemicals shall beused in all tests.Unless otherwise indicated,it is intended thatall reagents shall conform to the specifications of
12、 the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.3Other 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.3.2 Purity of
13、WaterUnless otherwise indicated,referencesto water shall be understood to mean reagent water conformingto Specification D1193.1These methods are under the jurisdiction of ASTM Committee D14 onAdhesives and are the direct responsibility of Subcommittee D14.80 on MetalBonding Adhesives.Current edition
14、 approved June 1,2021.Published June 2021.Originallyapproved in 1967.Last previous edition approved in 2012 as D2674 72(2012).DOI:10.1520/D2674-72R21.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards
15、 volume information,refer to the standards Document Summary page onthe ASTM website.3ACS Reagent Chemicals,Specifications and Procedures for Reagents andStandard-Grade Reference Materials,American Chemical Society,Washington,DC.For suggestions on the testing of reagents not listed by the American Ch
16、emicalSociety,see Analar Standards for Laboratory Chemicals,BDH Ltd.,Poole,Dorset,U.K.,and the United States Pharmacopeia and National Formulary,U.S.Pharma-copeial Convention,Inc.(USPC),Rockville,MD.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of Internation
