ASTM_G_42_-_11.pdf

Designation:G4211Standard Test Method forCathodic Disbonding of Pipeline Coatings Subjected toElevated Temperatures1This standard is issued under the fixed designation G42;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 test method describes an accelerated procedure fordetermining comparative characteristics of insulating coatingsystems applied to steel pipe exterior for the purpose ofpreventing or mitigating corrosion that may occur in under-ground service where the pipe will be exposed to hightemperatures and is under cathodic protection.This test methodis intended for use with samples of coated pipe taken fromcommercial production and is applicable to such samples whenthe coating is characterized by function as an electrical barrier.1.2 This test method is intended for testing coatings sub-merged or immersed in the test solution at elevated tempera-ture.When it is impractical to submerge or immerse the testspecimen,Test Method G95 may be considered where the testcell is cemented to the surface of the coated pipe specimen.Ifroom temperatures are required,see Test Methods G8.If aspecific test method is required with no options,see TestMethod G80.1.3 The values stated in SI units to three significant deci-mals are to be regarded as the standard.The values given inparentheses are for information only.1.4 WarningMercury has been designated by EPA andmany state agencies as a hazardous material that can causecentral nervous system,kidney,and liver damage.Mercury,orits vapor,may be hazardous to health and corrosive tomaterials.Caution should be taken when handling mercury andmercury-containing products.See the applicable product Ma-terial Safety Data Sheet(MSDS)for details and EPAs website(http:/www.epa.gov/mercury/faq.htm)for additional informa-tion.Users should be aware that selling mercury or mercury-containing products,or both,in your state may be prohibited bystate law.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:2G8 Test Methods for Cathodic Disbonding of Pipeline Coat-ingsG12 Test Method for Nondestructive Measurement of FilmThickness of Pipeline Coatings on Steel(Withdrawn2013)3G80 Test Method for Specific Cathodic Disbonding of Pipe-line Coatings(Withdrawn 2013)3G95 Test Method for Cathodic Disbondment Test of PipelineCoatings(Attached Cell Method)E1 Specification for ASTM Liquid-in-Glass ThermometersE2251 Specification for Liquid-in-Glass ASTM Thermom-eters with Low-Hazard Precision Liquids3.Summary of Test Method3.1 This test method subjects the coating on the test speci-men to electrical stress in a highly conductive electrolyte.Thecoating is artificially perforated before starting the test.Theelectrical stress is produced by connecting the test specimen tothe negative terminal of a source of direct current and byconnecting an anode to the positive terminal.Electrical instru-mentation is provided for measuring the current flowing in thecell.The electrical potential is also measured and the specimenis physically examined at intervals during the test period andupon conclusion of the test.3.1.1 The cathodic stress is applied under conditions of aconstant-elevated temperature.4.Significance and Use4.1 Damage to pipe coating is almost unavoidable duringtransportation and construction.Breaks or holidays in pipecoatings may expose the pipe to possible corrosion since,after1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings,Materials,and Applications and is the direct responsibility ofSubcommittee D01.48 on Durability of Pipeline Coating and Linings.Current edition approved Nov.15,2011.Published January 2012.Originallyapproved in 1975.Last previous edition approved in 2003 as G42 96(2003).DOI:10.1520/G0042-11.2For 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.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 a pipe has been installed underground,the surrounding earthwill be moisture-bearing and will constitute an effectiveelectrolyte.Applied cathodic protection potentials may causeloosening of the coating,beginning at holiday edges.Sponta-neous holidays may also be caused by such potentials.This testmethod provides acc