ASTM_G_37_-_98_2016.pdf

Designation:G3798(Reapproved 2016)Standard Practice forUse of Mattssons Solution of pH 7.2 to Evaluate the Stress-Corrosion Cracking Susceptibility of Copper-Zinc Alloys1This standard is issued under the fixed designation G37;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.1.Scope1.1 This practice covers the preparation and use of Matts-sons solution of pH 7.2 as an accelerated stress-corrosioncracking test environment for brasses(copper-zinc base al-loys).The variables(to the extent that these are known atpresent)that require control are described together with pos-sible means for controlling and standardizing these variables.1.2 This practice is recommended only for brasses(copper-zinc base alloys).The use of this test environment is notrecommended for other copper alloys since the results may beerroneous,providing completely misleading rankings.This isparticularly true of alloys containing aluminum or nickel asdeliberate alloying additions.1.3 This practice is intended primarily where the test objec-tive is to determine the relative stress-corrosion crackingsusceptibility of different brasses under the same or differentstress conditions or to determine the absolute degree of stresscorrosion cracking susceptibility,if any,of a particular brass orbrass component under one or more specific stress conditions.Other legitimate test objectives for which this test solution maybe used do,of course,exist.The tensile stresses present may beknown or unknown,applied or residual.The practice may beapplied to wrought brass products or components,brasscastings,brass weldments,and so forth,and to all brasses.Strict environmental test conditions are stipulated for maxi-mum assurance that apparent variations in stress-corrosionsusceptibility are attributable to real variations in the materialbeing tested or in the tensile stress level and not to environ-mental variations.1.4 This practice relates solely to the preparation andcontrol of the test environment.No attempt is made torecommend surface preparation or finish,or both,as this mayvary with the test objectives.Similarly,no attempt is made torecommend particular stress-corrosion test specimen configu-rations or methods of applying the stress.Test specimenconfigurations that may be used are referenced in Practice G30and STP 425.21.5 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.6 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.(For more specificsafety hazard statements see Section 8.)2.Referenced Documents2.1 ASTM Standards:3D1193 Specification for Reagent WaterG30 Practice for Making and Using U-Bend Stress-Corrosion Test Specimens3.Summary of Practice3.1 The practice consists of completely and continuouslyimmersing a stressed test specimen in an aqueous solutioncontaining 0.05 g-atom/L of Cu+and 1 g-mol/L of NH4+andof pH 7.2.The copper is added as CuSO45H2O and the NH4+as a mixture of NH4OH and(NH4)2SO4.The ratio of theselatter two compounds is adjusted to give the desired pH.Exposure time,criterion of failure,and so forth,are variableand not specifically recommended.4.Significance and Use4.1 This test environment is believed to give an acceleratedranking of the relative or absolute degree of stress-corrosioncracking susceptibility for different brasses.It has been foundto correlate well with the corresponding service ranking inenvironments that cause stress-corrosion cracking which isthought to be due to the combined presence of traces of1This 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 May 1,2016.Published May 2016.Originallyapproved in 1973.Last previous edition approved in 2011 as G37 98(2011).DOI:10.1520/G0037-98R16.2STP425,Stress Corrosion Testing,ASTM International.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 moisture and ammonia vapor.The extent to which the accel-erated ranking correlates with the ranking obtained afterlong-term exposure to environments containing corrodentsother than ammonia is not at present known.Examples of suchenvironments may be severe marine atmospheres(C