ASTM_G_186_-_05_2011.pdf

Designation:G18605(Reapproved 2011)Standard Test Method forDetermining Whether Gas-Leak-Detector Fluid SolutionsCan Cause Stress Corrosion Cracking of Brass Alloys1This standard is issued under the fixed designation G186;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.1.Scope1.1 This test method covers an accelerated test method forevaluating the tendency of gas leak detection fluids(LDFs)tocause stress corrosion cracking(SCC)of brass components incompressed gas service.1.2 The values stated in inch-pound units are to be regardedas standard.The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.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 to determine theapplicability of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2B135 Specification for Seamless Brass TubeB135M Specification for Seamless Brass Tube MetricD1193 Specification for Reagent WaterG1 Practice for Preparing,Cleaning,and Evaluating Corro-sion Test SpecimensG15 Terminology Relating to Corrosion and Corrosion Test-ing(Withdrawn 2010)3G37 Practice for Use of Mattssons Solution of pH 7.2 toEvaluate the Stress-Corrosion Cracking Susceptibility ofCopper-Zinc AlloysG38 Practice for Making and Using C-Ring Stress-Corrosion Test Specimens3.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 Gas Leak Detector SolutionsAlso known as leakdetection fluids,leak detector solutions,bubble solutions,andsoap solutions,designated in this standard as LDFs,are fluidsused to detect leaks in pressurized gas systems by the forma-tion of bubbles at the leak site.3.1.2 The terminology used herein,if not specifically de-fined otherwise,shall be in accordance with Terminology G15.4.Summary of Test Method4.1 This test method consists of three steps:The first stepconsists of running a sample of the test specimens to verify thatthey are susceptible to stress corrosion cracking using Matts-sons Solution(see Practice G37).The second step is to exposethe specimens to a solution that does not cause SCC to verifythat the test environment does not contain components that cancause SCC to brass.The third step is to test the LDF todetermine if it causes SCC of the brass specimens within 15wetting and evaporation cycles.4.2 The specimen used in this test is a C-ring stressed tocreate at least 0.65%strain in the outer fibers of the specimen.4.3 Macroscopic examination of the specimens is carriedout after every second wetting cycle and if cracking issuspected the specimen is examined at higher magnificationsfor confirmation.Metallographic sectioning through thestressed area is used to verify minor cracking at the end of thefifteen cycles.4.4 LDFs that cause SCC in any specimens within 15wetting cycles are considered to have failed this test and notsuitable for use in pressurized gas systems with brass compo-nents.5.Significance and Use5.1 Brass components are routinely used in compressed gasservice for valves,pressure regulators,connectors and manyother components.Although soft brass is not susceptible toammonia SCC,work-hardened brass is susceptible if itshardness exceeds about 54 HR 30T(55HRB)(Rockwell scale).Normal assembly of brass components should not inducesufficient work hardening to cause susceptibility to ammonia1This test method 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 March 1,2011.Published April 2011.Originallyapproved in 2005.Last previous edition approved in 2005 as G18605.DOI:10.1520/G0186-05R11.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 SCC.However,it is has been observed that over-tightening ofthe components will render them susceptible to SCC,and theproblem becomes more severe in older components that havebeen tightened many times.In this test,the specimens areobtained in the hardened condition and are strained beyond theelastic limit to accelerate the tendency towards SCC.5.2 It is normal practice to use LDFs to check pressurizedsystems to assure that leaking is not occurring.LDFs areusually aqueous solutions c