ASTM_G_103_-_97_2011.pdf

Designation:G10397(Reapproved 2011)Standard Practice forEvaluating Stress-Corrosion Cracking Resistance of LowCopper 7XXX Series Al-Zn-Mg-Cu Alloys in Boiling 6%Sodium Chloride Solution1This standard is issued under the fixed designation G103;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.INTRODUCTIONContinuous immersion in boiling 6%sodium chloride solution historically was considered to be aneffective accelerated SCC testing medium for allAl-Zn-Mg-Cu alloys(1,2),2but in more recent years,alternate immersion in 3.5%sodium chloride solution(Practice G44)has become the favored testmedium for the high copper(1.2 to 2.6%Cu)7XXX series alloys(3,4).Evidence to date shows,however,that the boiling 6%sodium chloride medium correlates better with outdoor atmosphericexposure than Practice G44 for the 7XXX series alloys containing little or no copper(5,6,7,8).1.Scope1.1 This practice primarily covers the test medium whichmay be used with a variety of test specimens and methods ofapplying stress.Exposure times,criteria of failure,and so on,are variable and not specified.1.2 This stress-corrosion testing practice is intended forstatically loaded smooth non-welded or welded specimens of7XXX series Al-Zn-Mg-Cu alloys containing less than 0.26%copper.1.3 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.See Section 8 foradditional precautions.2.Referenced Documents2.1 ASTM Standards:3B580 Specification for Anodic Oxide Coatings on Alumi-numD1193 Specification for Reagent WaterG30 Practice for Making and Using U-Bend Stress-Corrosion Test SpecimensG38 Practice for Making and Using C-Ring Stress-Corrosion Test SpecimensG39 Practice for Preparation and Use of Bent-Beam 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 SpecimensG58 Practice for Preparation of Stress-Corrosion Test Speci-mens for Weldments3.Summary of Practice3.1 Stressed specimens are totally and continuously im-mersed in boiling 6%sodium chloride solution for up to 168 h.Various types of smooth test specimens and methods ofstressing may be used.Performance is based on time to visualcracking.4.Significance and Use4.1 This practice is normally used for stress-corrosionscreening for the development ofAl-Zn-Mg-Cu alloys contain-ing less than 0.26%copper.Effects on stress-corrosion resis-tance due to variables such as composition,thermo-mechanicalprocessing,other fabrication variables,and magnitude ofapplied stress may be compared.1This practice is under the jurisdiction of ASTM Committee G01 on Corrosionof Metals and is the direct responsibility of Subcommittee G01.06 on Environmen-tally Assisted Cracking.Current edition approved March 1,2011.Published April 2011.Originallyapproved in 1989.Last previous edition approved in 2005 as G10397(2005).DOI:10.1520/G0103-97R11.2The boldface numbers in parentheses refer to the list of references at the end ofthis standard.3For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 4.2 For a given mechanical method of stressing,the relativestress-corrosion resistance of the low copper Al-Zn-Mg-Cualloys in atmospheric exposure correlates better with perfor-mance in boiling 6%sodium chloride solution than with otheraccelerated testing media(7-9).In addition,this practice isrelatively rapid.4.3 This practice is not applicable to 2XXX(Al-Cu),5XXX(Al-Mg),6XXX(Al-Mg-Si),and the 7XXX(Al-Zn-Mg-Cu)series alloys containing more than 1.2%copper.4.3.1 For 7XXX series alloys containing between 0.26%and 1.2%copper,there is no general agreement as to whetherthis practice or Practice G44 correlates better with stress-corrosion resistance in service(5-8,10).5.Apparatus5.1 Fig.1 illustrates one type of apparatus that has beenused.5.2 Materials of Construction:5.2.1 Materials of construction that come in contact with theboiling salt solution shall be such that they are not affected bythe corrodent to an extent that they can cause contamination ofthe solution and change its corrosiveness.5.2.2 Use of glass or aluminum containers and condensers isrecommended.5.2.3 Metallic materials of construction should be limited tocopper free aluminum all