Field Procedures to Estimate Corrosion Potentials and Rates and Cathodic Protection Penetration Limit in a Coating Disbonded Region on Buried Pipelines

Abstract No field method or procedure exists to measure the effectiveness of cathodic protection (CP) in a coating disbonded region on buried pipelines; however, gaining this capability can be useful to assist the pipeline industry in better control of the pipeline external corrosion. This paper reports two field procedures to estimate the corrosion potentials and rates in a coating disbonded region on buried pipelines and a method to estimate the maximum distance that CP current can penetrate into a coating disbonded region from the holiday. The above estimates can be accomplished through the use of sampled near-pipe soil chemistry, measured pipe native or rest potential, CP “instant-off” potential, and a corrosion rate of the pipe steel measured in simulated soil groundwater in deaerated condition. The field procedures can be implemented without the need of excavations to expose the pipeline surface. The corrosion rates thus determined can be used to assist in prioritizing corrosion susceptible location...