This Association for Materials Protection and Performance (AMPP) standard test method presents guidelines and procedures for use primarily by corrosion control personnel in the pipeline industry to determine the general condition of a pipeline coating. These techniques are used to measure the coating conductance (inverse of coating resistance) on sections of underground pipelines. This test method applies only to pipe coated with dielectric coatings.

When surveying a coated pipeline system, it may be necessary to determine the conductance of the coating. The conductance of a coating can vary considerably along the pipeline. Variations may be caused by changes in average soil resistivity, terrain, and quality of construction. To obtain data for coating conductance calculations, interrupted structure-to-electrolyte potentials and line current readings are taken at pre-selected intervals. It should be noted that the average soil resistivity has a direct effect on the coating conductance measurement. Because soil resistivity can affect the coating conductance, it must be known when evaluating a section of a pipeline coating.