1、Designation:G896(Reapproved 2010)Standard Test Methods forCathodic Disbonding of Pipeline Coatings1This standard is issued under the fixed designation G8;the number immediately following the designation indicates the year of originaladoption or,in the case of revision,the year of last revision.Anumb
2、er in parentheses indicates the year of last reapproval.Asuperscriptepsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 These test methods cover accelerated procedures forsimultaneously determining comparative characteristics of in-sulating coating systems applied
3、 to steel pipe exterior for thepurpose of preventing or mitigating corrosion that may occur inunderground service where the pipe will be in contact withinland soils and may or may not receive cathodic protection.They are intended for use with samples of coated pipe takenfrom commercial production an
4、d are applicable to suchsamples when the coating is characterized by function as anelectrical barrier.1.2 This test method is intended for testing coatings sub-merged or immersed in the test solution at room temperature.When it is impractical to submerge or immerse the testspecimen,Test Method G95 m
5、ay be considered where the testcell is cemented to the surface of the coated pipe specimen.Ifhigher temperatures are required,see Test Method G42.If aspecific test method is required with no options,see TestMethod G80.1.3 The values stated in SI units to 3 significant decimals areto be regarded as t
6、he standard.The values given in parenthesesare for information only.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 appl
7、ica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2G12 Test Method for Nondestructive Measurement of FilmThickness of Pipeline Coatings on Steel(Withdrawn2013)3G42 Test Method for Cathodic Disbonding of PipelineCoatings Subjected to Elevated TemperaturesG80 T
8、est Method for Specific Cathodic Disbonding of Pipe-line Coatings(Withdrawn 2013)3G95 Test Method for Cathodic Disbondment Test of PipelineCoatings(Attached Cell Method)3.Summary of Test Method3.1 Both of the two test methods described subject thecoating on the test specimen to electrical stress in
9、a highlyconductive,alkaline electrolyte.Electrical stress is obtainedeither by means of a sacrificial magnesium anode or from animpressed current system.The coating is perforated beforestarting the test.3.1.1 In Method A,a magnesium anode is used with noelectrical monitoring during the test period.T
10、he results aredetermined by physical examination after the test period isconcluded.3.1.2 In Method B,either a magnesium anode or an im-pressed current system may be used.Electrical instrumentationis provided for measuring the current in the cell circuit.Theelectrical potential is also measured,and u
11、pon conclusion ofthe test period,the test specimen is physically examined.3.1.3 In both test methods physical examination is con-ducted by comparing the extent of loosened or disbondedcoating at the perforations in the immersed area with extent ofloosened or disbonded coating at a new test hole in t
12、he coatingmade in an area that was not immersed.4.Significance and Use4.1 Breaks or holidays in pipe coatings may expose the pipeto possible corrosion,since after a pipe has been installedunderground,the surrounding earth will be more or lessmoisture-bearing and it constitutes an effective electroly
13、te.Damage to pipe coating is almost unavoidable during trans-portation and construction.Normal soil potentials as well asapplied cathodic protection potentials may cause loosening ofthe coating,beginning at holiday edges,in some cases increas-ing the apparent size of the holiday.Holidays may also be
14、1These test methods are under the jurisdiction of ASTM Committee D01 onPaint and Related Coatings,Materials,and Applications and are the directresponsibility of Subcommittee D01.48 on Durability of Pipeline Coating andLinings.Current edition approved Dec.1,2010.Published December 2010.Originallyappr
15、oved in 1969.Last previous edition approved in 2003 as G8 96(2003)1.DOI:10.1520/G0008-96R10.2For 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 Summar
16、y 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 caused by such potentials.While apparently loosened coatingand cathodic holidays may not result in corrosion,this testprovides accelerated conditions for loosening to occur andtherefore gives a measure of resistance of coatings to this typeof action.4.2 The effects of the test ma
