ASTM_G_91_-_11.pdf

Designation:G9111Standard Practice forMonitoring Atmospheric SO2Deposition Rate forAtmospheric Corrosivity Evaluation1This standard is issued under the fixed designation G91;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 two methods of monitoring atmo-spheric sulfur dioxide,SO2deposition rates with specificapplication for estimating or evaluating atmospheric corrosiv-ity as it applies to metals commonly used in buildings,structures,vehicles and devices used in outdoor locations.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.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.2.Referenced Documents2.1 ASTM Standards:2D516 Test Method for Sulfate Ion in WaterD1193 Specification for Reagent WaterD2010/D2010M Test Methods for Evaluation of Total Sul-fation Activity in the Atmosphere by the Lead DioxideTechniqueG16 Guide for Applying Statistics to Analysis of CorrosionDataG84 Practice for Measurement of Time-of-Wetness on Sur-faces Exposed to Wetting Conditions as in AtmosphericCorrosion TestingG140 Test Method for Determining Atmospheric ChlorideDeposition Rate by Wet Candle MethodG193 Terminology and Acronyms Relating to Corrosion2.2 ISO Standards:3ISO 9225 Corrosion of metals and alloys-Corrosivity ofatmospheres Measurement of environmental parametersaffecting corrosivity of atmospheres3.Terminology3.1 DefinitionsThe terminology used herein shall be inaccordance with Terminology and Acronyms G193.4.Summary of Practice4.1 Sulfation plates consisting of a lead peroxide reagent inan inverted dish are exposed for 30-day intervals.The platesare recovered and sulfate analyses performed on the contents todetermine the extent of sulfur capture.Lead peroxide cylindersare also used for monitoring atmospheric SO2in a similarmanner.The results are reported in terms of milligrams of SO2per square metre per day.5.Significance and Use5.1 Atmospheric corrosion of metallic materials is a func-tion of many weather and atmospheric variables.The effect ofspecific corrodants,such as sulfur dioxide,can accelerate theatmospheric corrosion of metals significantly.It is important tohave information available for the level of atmospheric SO2when many metals are exposed to the atmosphere in order todetermine their susceptibility to corrosion damage during theirlife time in the atmosphere.5.2 Volumetric analysis of atmospheric SO2concentrationcarried out on a continuous basis is considered by someinvestigators as the most reliable method of estimating theeffects caused by this gas.However,these methods requiresophisticated monitoring devices together with power suppliesand other equipment that make them unsuitable for manyexposure sites.These methods are beyond the scope of thispractice.5.3 The sulfation plate method provides a simple techniqueto independently monitor the level of SO2in the atmosphere toyield a weighted average result.The lead peroxide cylinder is1This practice is under the jurisdiction of ASTM Committee G01 on Corrosionof Metals and is the direct responsibility of Subcommittee G01.04 on AtmosphericCorrosion.Current edition approved Nov.1,2011.Published December 2011.Originallyapproved in 1986.Last previous edition approved in 2010 as G9197(2010).DOI:10.1520/G0091-11.2For 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.3Available from International Organization for Standardization(ISO),1,ch.dela Voie-Creuse,CP 56,CH-1211 Geneva 20,Switzerland,http:/www.iso.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 similar technique that produces comparable results,and theresults are more sensitive to low levels of SO2.5.4 Sulfation plate or lead peroxide cylinder results may beused to characterize atmospheric corrosion test sites regardingthe effective average level of SO2in the atmosphere at theselocations.5.5 Either sulfation plate or lead peroxide cylinder testing isuseful in determining microclimate,seasonal,and long termvariations in the effective average level of SO2.5.6 The results of these sulfur dioxide deposition rate testsmay be used in correlations of atmospheric corrosion rates withatmospheric data to determine the sensitivity of the corrosionrate to SO2level.5.7 The sulfur dioxide monitoring methods may