ASTM_G_47_-_98_2011.pdf

Designation:G4798(Reapproved 2011)Standard Test Method forDetermining Susceptibility to Stress-Corrosion Cracking of2XXX and 7XXX Aluminum Alloy Products1This standard is issued under the fixed designation G47;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 uniform procedure for char-acterizing the resistance to stress-corrosion cracking(SCC)ofhigh-strength aluminum alloy wrought products for the guid-ance of those who perform stress-corrosion tests,for those whoprepare stress-corrosion specifications,and for materials engi-neers.1.2 This test method covers method of sampling,type ofspecimen,specimen preparation,test environment,and methodof exposure for determining the susceptibility to SCC of 2XXX(with 1.8 to 7.0%copper)and 7XXX(with 0.4 to 2.8%copper)aluminum alloy products,particularly when stressed inthe short-transverse direction relative to the grain structure.1.3 The values stated in SI units are to be regarded asstandard.The inch-pound units in parentheses are provided forinformation.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:2G38 Practice for Making and Using C-Ring Stress-Corrosion Test SpecimensG44 Practice for Exposure of Metals andAlloys byAlternateImmersion in Neutral 3.5%Sodium Chloride SolutionG49 Practice for Preparation and Use of Direct TensionStress-Corrosion Test SpecimensG139 Test Method for Determining Stress-Corrosion Crack-ing Resistance of Heat-Treatable Aluminum Alloy Prod-ucts Using Breaking Load Method3.Summary of Test Method3.1 This test method provides a comprehensive procedurefor accelerated stress-corrosion testing high-strength aluminumalloy product forms,particularly when stressed in the short-transverse grain direction.It specifies tests of constant-strain-loaded,3.18-mm(0.125-in.)tension specimens or C-ringsexposed to 3.5%sodium chloride(NaCl)solution by alternateimmersion,and includes procedures for sampling variousmanufactured product forms,examination of exposed testspecimens,and interpretation of test results.4.Significance and Use4.1 The 3.5%NaCl solution alternate immersion test pro-vides a test environment for detecting materials that would belikely to be susceptible to SCC in natural outdoor environ-ments,especially environments with marine influences.3,4,5Fordetermining actual serviceability of a material,other stress-corrosion tests should be performed in the intended serviceenvironment under conditions relating to the end use,includingprotective measures.4.2 Although this test method is intended for certain alloytypes and for testing products primarily in the short-transversestressing direction,this method is useful for some other typesof alloys and stressing directions.5.Interferences5.1 A disadvantage of the 3.5%NaCl solution alternateimmersion test is that severe pitting may develop in the1This test method,which was developed by a joint task group with theAluminum Association,Inc.,is under the jurisdiction of ASTM Committee G01 onCorrosion of Metals and is the direct responsibility of Subcommittee G01.06 onEnvironmentally Assisted Cracking.Current edition approved Sept.1,2011.Published September 2011.Originallyapproved in 1976.Last previous edition approved in 2004 as G4798(2004).DOI:10.1520/G0047-98R11.2For 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.3Romans,H.B.,Stress Corrosion Testing,ASTM STP 425,ASTM,1967,pp.182208.4Brown,R.H.,Sprowls,D.O.,and Shumaker,M.B.,“The Resistance ofWrought High Strength Aluminum Alloys to Stress Corrosion Cracking,”StressCorrosion Cracking of MetalsA State of the Art,ASTM STP 518,ASTM,1972,pp.87118.5Sprowls,D.O.,Summerson,T.J.,Ugiansky,G.M.,Epstein,S.G.,and Craig,H.L.,Jr.,“Evaluation of a Proposed Standard Method of Testing for Susceptibilityto Stress-Corrosion Cracking of High-Strength 7XXX Series Aluminum AlloyProducts,”Stress Corrosion-New Approaches,ASTM STP 610,ASTM,1976,pp.331.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 specimens.Such pitting in tension specimens with relativelysmall cross section can markedly reduce the effective cross-sectional area and produce a net section stress greater than thenominal gross section stress,resulting in ei