ASTM_G_55_-_07_2013.pdf

Designation:G5507(Reapproved 2013)Standard Test Method forEvaluating Pipeline Coating Patch Materials1This standard is issued under the fixed designation G55;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 provides an accelerated means ofdetermining the relative sealing abilities of pipeline patchingmaterials that are used to seal holidays in pipeline coatings onsteel pipe.This test method is intended for utilization ofspecimens of pipeline coatings on small-diameter pipe,forrepresenting coatings used for buried or submerged service,and where the purpose of the coating is to provide an electricalbarrier between the steel pipe and its environment.1.2 This test method is not intended for evaluating patchmaterials that are overlapped upon themselves.1.3 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.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.Summary of Test Method2.1 Patched pipeline coating specimens are suspended in anaqueous,alkaline,low-resistivity electrolyte.The specimensare individually connected to a magnesium anode or rectifier ata point external to the electrolyte.The coated,patched pipelinespecimens are sealed at the base and at all other areas exceptthe patch boundaries,such that the only paths for current floware at the boundaries of the patches.Current flow in each patcharea is averaged from monthly readings taken for one year.3.Significance and Use3.1 Holidays in pipeline coatings may be repaired bycircumferential wrapping with a suitable pipe wrap tape.However,this technique is not always practicable and patchingmay be required.The effectiveness of a patch material dependsupon its adhesion to the original pipeline coating to effectsealing.3.2 The results of this accelerated test have been found toyield comparative data useful for the selection of patchingmaterials.The user is cautioned against the use of this methodfor absolute material properties characterization.3.3 This procedure provides an accelerated method byexposing the patch to a severe radius of curvature on small-diameter pipe.The specimen is also exposed to a stress voltagein the presence of a highly conductive electrolyte.4.Apparatus4.1 Test VesselA cylindrical glass battery jar(orequivalent),approximately 300 mm(12 in.)in diameter and300 mm in height.One magnesium anode shall be contained ineach battery jar,with a maximum of eight pipe specimens,andwith each specimen measuring about 25 mm(1 in.)in diameterby approximately 300 mm in length of coated pipe.(See 4.3and Fig.1 and Fig.2.)4.2 SuspensionThe suspension ring for supporting thepipe specimens shall be an electrically nonconductive circulardisk,measuring approximately 300 mm(12 in.)in diameterand approximately 5 mm(316in.)in thickness.(See 6.4.)Drilla 15-mm(12-in.)diameter hole through the center of the ringfor external extension of the anode lead wire.Drill eightsuspension holes,about 45 mm(134in.)in diameter,throughthe suspension ring for the pipe specimens;these holes shall becentered 110 mm(412in.)from the center of the suspensionring and evenly spaced around the ring at 45 increments asmeasured from the center of the suspension ring.4.3 PotentialA high-purity magnesium anode shall beused,weighing approximately 2.3 kg(5 lb),and having anopen-circuit potential of approximately 1.7 d-c V relative to acopper-copper sulfate electrode,and complete with a factory-sealed lead wire.The magnesium anode may be replaced by acontrolled d-c voltage from a rectifier,and then maintaining thepotential between the specimen having the least current flowand a copper-copper sulfate reference cell(with the cell beingproperly immersed in the electrolyte)at 1.50 6 0.05 d-c V.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings,Materials,and Applicationsand is the direct responsibility ofSubcommittee D01.48 on Durability of Pipeline Coating and Linings.Current edition approved June 1,2013.Published June 2013.Originallyapproved in 1977.Last previous edition approved in 2007 as G55 07.DOI:10.1520/G0055-07R13.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1(See Note 1.)The anode should be composed of a suitablenonconsumable material.2This option will avoid the precipi-tation of magnesium salts on the specimens.NOTE1The potential of the magnesium anode will approximate thisrange over the life of the test.If a calomel electrod