ASTM_G_44_-_99_2013.pdf

Designation:G4499(Reapproved 2013)Standard Practice forExposure of Metals and Alloys by Alternate Immersion inNeutral 3.5%Sodium Chloride Solution1This standard is issued under the fixed designation G44;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 practice covers procedures for making alternateimmersion stress corrosion tests in 3.5%sodium chloride(NaCl)(Note 1).It is primarily for tests of aluminum alloys(Test Method G47)and ferrous alloys,but may be used forother metals exhibiting susceptibility to chloride ions.It setsforth the environmental conditions of the test and the means forcontrolling them.NOTE1Alternate immersion stress corrosion exposures are some-times made in substitute ocean water(without heavy metals)prepared inaccordance with Specification D1141.The general requirements of thispresent practice are also applicable to such exposures except that thereagents used,the solution concentration,and the solution pH should be asspecified in Specification D1141.1.2 This practice can be used for both stressed and un-stressed corrosion specimens.Historically,it has been used forstress-corrosion cracking testing,but is often used for otherforms of corrosion,such as uniform,pitting,intergranular,andgalvanic.1.3 This practice is intended for alloy development and forapplications where the alternate immersion test is to serve as acontrol test on the quality of successive lots of the samematerial.Therefore,strict test conditions are stipulated formaximum assurance that variations in results are attributable tovariations in the material being tested.1.4 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.1.5 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:2D1141 Practice for the Preparation of Substitute OceanWaterD1193 Specification for Reagent WaterE3 Guide for Preparation of Metallographic SpecimensG1 Practice for Preparing,Cleaning,and Evaluating Corro-sion Test SpecimensG16 Guide for Applying Statistics to Analysis of CorrosionDataG47 Test Method for Determining Susceptibility to Stress-Corrosion Cracking of 2XXX and 7XXX AluminumAlloy Products3.Summary of Practice3.1 The alternate immersion test utilizes a 1-h cycle thatincludes a 10-min period in an aqueous solution of 3.5%sodium chloride(NaCl)followed by a 50-min period out of thesolution,during which the specimens are allowed to dry.This1-h cycle is continued 24 h/day for the total number of daysrecommended for the particular alloy being tested.Typically,aluminum and ferrous alloys are exposed from 20 to 90 days orlonger,depending upon the resistance of the alloy to corrosionby saltwater.4.Significance and Use4.1 The 3.5%NaCl alternate immersion procedure is ageneral,all-purpose procedure that produces valid comparisonsfor most metals,particularly when specimens are exposed athigh levels of applied stress or stress intensity.4.2 While the alternate immersion test is an accelerated testand is considered to be representative of certain naturalconditions,it is not intended to predict performance in special-ized chemical environments in which a different mode ofcracking may be operative.For example,it does not predict theperformance of aluminum alloys in highly acidic environments1This 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 1,2013.Published July 2013.Originally approvedin 1975.Last previous edition approved in 2005 as G44 99(2005).DOI:10.1520/G0044-99R13.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 such as heated inhibited red fuming nitric acid(IRFNA).Forsuch cases,the results of the alternate immersion test are ofdoubtful significance until a relationship has been establishedbetween it and anticipated service environments.4.3 While this practice is applicable in some degree to allmetals,it is not equally discriminative of all alloys,even withinthe same metal system.Consequently,information should beestablished to allow comparisons