ASTM_D_6676_-_D_6676M_-_13.pdf

Designation:D6676/D6676M13Standard Test Method forCathodic Disbonding of Exterior Pipeline Coatings atElevated Temperatures Using Interior Heating1This standard is issued under the fixed designation D6676/D6676M;the number immediately following the designation indicates theyear of original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of lastreapproval.A superscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method describes an accelerated procedure fordetermining comparative characteristics of coating systemsapplied to the exterior of steel pipe for the purpose ofpreventing or mitigating corrosion that may occur in under-ground or immersion where the pipe is carrying heated mediaand is under cathodic protection.This test method is intendedfor use with samples of coated pipe,or with a specimen cutfrom the section of coated pipe or flat plates,and is applicableto such samples when the coating is characterized by functionas an electrical barrier.1.2 This test method is intended to simulate conditionswhen external coatings are exposed to high temperature insidethe pipe and to an ambient temperature outside,and thus aresubjected to temperature gradient.If elevated temperatures arerequired but without temperature gradient,see Test MethodG42.1.3 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard.The values stated ineach system may not be exact equivalents;therefore,eachsystem shall be used independently of the other.Combiningvalues from the two systems may result in non-conformancewith the standard.1.4 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)3G42 Test Method for Cathodic Disbonding of PipelineCoatings Subjected to Elevated TemperaturesG62 Test Methods for Holiday Detection in Pipeline Coat-ingsG95 Test Method for Cathodic Disbondment Test of PipelineCoatings(Attached Cell Method)3.Summary of Test Method3.1 The test method described,subjects the coating on thetest specimen to electrical stress in a highly conductive alkalineelectrolyte.Electrical stress is obtained from an impresseddirect-current system.An intentional holiday is to be made inthe coating prior to starting of test.3.1.1 Electrical instrumentation is provided for measuringthe current and the potential throughout the test cycle.At theconclusion of the test period,the test specimen is physicallyexamined.3.1.2 Physical examination is conducted by comparing theextent of loosened or disbonded coating at the intentionalholiday in the immersed area with extent of loosened ordisbonded coating at a reference holiday made in the coating inan area that was not immersed.3.1.3 The cathodic stress is applied under conditions of aconstant temperature gradient,simulating a heated pipelinewith an exterior coating.3.1.4 Specimens that can be used are:(a)piece of pipe(Fig.1)or(b)samples cut from pipe or flat plate(Fig.2 and Fig.3).3.1.4.1 Some coatings rely on application tension(such astape)for maximum cathodic disbondment resistance.Cutcoupons or flat plates must not be used.4.Significance and Use4.1 Damage to a pipe coating is almost unavoidable duringtransportation and construction.Breaks or holidays in pipe1This 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.1,2013.Published November 2013.Originallyapproved in 2001.Last previous edition approved in 2001 as D6676 011whichwas withdrawn January 2010 and reinstated in November 2013.DOI:10.1520/D6676_D6676M-13.2For 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 coatings may expose the pipe to possible corrosion since,aftera 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.Usuallyexterior pipeline coatings applied over pipes