ASTM_D_6190_-_97.pdf

Designation:D 6190 97Standard Test Method forCathodic Disbonding of Pipeline Coatings by LaboratorySimulation of Soil Burial1This standard is issued under the fixed designation D 6190;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers an accelerated procedure fordetermining the relative disbonding characteristics of electri-cally insulating coating systems applied to steel pipe exteriors.The coating is applied for the purpose of preventing ormitigating corrosion that may occur in underground service.The pipe may be exposed to elevated temperatures while undercathodic protection.This test method is intended for use withsamples of coated pipe taken from commercial production andis applicable to such samples when the coating functions as anelectrical barrier.1.2 The values stated in SI units to three significant figuresare to regarded as the standard.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:E 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2G 12 Test Method for Nondestructive Measurement of FilmThickness of Pipeline Coatings on Steel3G 19 Test Method of Test for Disbonding Characteristics ofPipeline Coatings by Direct Soil Burial33.Summary of Test Method3.1 An apparatus is described in which soil is brought incontact with a coated pipe sample under conditions thatsimulate soil burial.The specimens with intentionally damagedareas are electrically connected to a rectifier to apply anelectrical stress.A highly conductive soil mixture consisting ofelectrolyte soaked sand is used to accelerate the test.After test,the disbonded areas of coating are removed and the exposedarea is measured.3.2 The cathodic stress may be applied under conditions ofa constant level elevated temperature.3.3 Physical examination is conducted by comparing theextent of loosened or disbonded coating at the perforations inthe soil exposed area with the extent of loosened or disbondedcoating at a new test hole in the coating made in an area thatwas not exposed to soil.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 aftera pipe has been installed underground,the surrounding soilcould be an effective electrolyte.These coatings are generallyused under cathodic protection conditions;damaged areas inthem can enlarge to an extent that would not allow the cathodicprotection to be effective.Elevated temperature increases thetendency of coatings to disbond,however,there may be aconsiderable difference in the tendency to disbond in theground and in the laboratory electrolyte test.It is thereforeappropriate for some coatings to test cathodic disbonding insoil both at room and elevated temperatures.The test isaccelerated by using sand soaked with electrolyte as theconducting medium.4.2 When compared to field testing of samples outdoors insoil,the method described here offers better control,uses lesssoil,and can be performed in the laboratory.In addition,theuse of highly conductive electrolyte-soaked sand results insignificant acceleration of the test over Test Method G 19.4.3 The physical examination is made easier by comparingthe adhesion of the coating to that obtained at a section notexposed to the soil.This is assumed to be the maximumadhesion or bond as measured by the lifting technique used andthat the same lifting technique can be used at a test hole thatwas exposed to the soil.This provides a means of comparingthe relative resistance to lifting.4.4 It is assumed that any relatively lesser bonded area at theexposed test holes in the coating was caused by electricalstressing.5.Apparatus5.1 The soil simulation test apparatus is shown schemati-cally in Fig.1.Drawings for the aluminum lower seal,plastictop plate,aluminum top seal,and plastic main body are shownin Fig.2.These drawings will enable the construction of an1This test method is under the jurisdiction of ASTM Committee D-1 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.10,1997.Published February 1998.2Annual Book of ASTM Standards,Vol 14.02.3Annual Book of ASTM Standards,Vol 06.02.1AMERICAN SOCIETY FOR TESTING AND MATERIALS100 Barr Harbor Dr.,West Conshohocken,PA 19428Reprinted from the Annual Book of ASTM Standards.Copy