ASTM_G_34_-_01_2013.pdf

Designation:G3401(Reapproved 2013)Standard Test Method forExfoliation Corrosion Susceptibility in 2XXX and 7XXXSeries Aluminum Alloys(EXCO Test)1This standard is issued under the fixed designation G34;the number immediately following the designation indicates the year of originaladoption or,in the case of revision,the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon()indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1.Scope1.1 This test method covers a procedure for constant im-mersion exfoliation corrosion(EXCO)testing of high-strength2XXX and 7XXX series aluminum alloys.NOTE1This test method was originally developed for research anddevelopment purposes;however,it is referenced,in specific materialspecifications,as applicable for evaluating production material(refer toSection 14 on Precision and Bias).1.2 This test method applies to all wrought products such assheet,plate,extrusions,and forgings produced from conven-tional ingot metallurgy process.1.3 This test method can be used with any form of specimenor part that can be immersed in the test solution.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:2D1193 Specification for Reagent WaterE3 Guide for Preparation of Metallographic SpecimensG15 Terminology Relating to Corrosion and Corrosion Test-ing(Withdrawn 2010)3G112 Guide for Conducting Exfoliation Corrosion Tests inAluminum Alloys2.2 ASTM Adjuncts:Illustrations(Enlarged Glossy Prints)43.Terminology3.1 Definitions:3.1.1 exfoliationcorrosion that proceeds laterally from thesites of initiation along planes parallel to the surface,generallyat grain boundaries,forming corrosion products that forcemetal away from the body of the material giving rise to alayered appearance(Terminology G15).4.Summary of Test Method4.1 This test method provides an accelerated exfoliationcorrosion test for 2XXX and 7XXX series aluminum alloysthat involves the continuous immersion of test materials in asolution containing 4 M sodium chloride,0.5 M potassiumnitrate,and 0.1 M nitric acid at 25 6 3C(77 6 5F).Thesusceptibilitytoexfoliationisdeterminedbyvisualexamination,with performance ratings established by refer-ence to standard photographs.5.Significance and Use5.1 This test method was originally developed for researchand development purposes;however,it is referenced,inspecific material specifications,as applicable for evaluatingproduction material(refer to Section 14 on Precision and Bias).5.2 Use of this test method provides a useful prediction ofthe exfoliation corrosion behavior of these alloys in varioustypes of outdoor service,especially in marine and industrialenvironments.5The test solution is very corrosive and repre-sents the more severe types of environmental service,excluding,of course,unusual chemicals not likely to beencountered in natural environments.1This test method is under the jurisdiction of ASTM Committee G01 onCorrosion of Metals and is the direct responsibility of Subcommittee G01.05 onLaboratory Corrosion Tests.Current edition approved May 1,2013.Published July 2013.Originally approvedin 1972.Last previous edition approved in 2007 as G3401(2007).DOI:10.1520/G0034-01R13.2For 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.3The last approved version of this historical standard is referenced onwww.astm.org.4Available from ASTM International Headquarters.Order Adjunct No.ADJG003402.Original adjunct produced in 1980.5Ketcham,S.J.,and Jeffrey,P.W.,“Exfoliation Corrosion Testing of 7178 and7075 Aluminum Alloys”(Report of ASTM G01.05 Interlaboratory Testing Programin Cooperation with the Aluminum Association);and Sprowls,D.O.,Walsh,J.D.,and Shumaker,M.B.,“Simplified Exfoliation Testing of Aluminum Alloys,”Localized CorrosionCause of Metal Failure,ASTM STP 516,ASTM,1972.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.3 The exfoliation ratings were arbitrarily chosen to illus-trate a wide range in resistance to exfoliation in this test.However,it remains to be determined whether correlations canbe established between EXCO test ratings and realistic serviceconditions for a given alloy.It is an ongoing activity of theTask Group on Exfoliation Corrosion of Aluminum Alloys(G01.05.02.08)to maintain outdoor exposure tests for thispurpose.For example,it has been reported6that samples ofAl-Zn-Mg-Cu alloys rated EAor Pin a 48-h EXCO test did notdevelop more than a