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

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 cut-rent can penetrate into a coating disbonded region from the holiday. The above estimates can be accomplished through Me 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 sur-face The corrosion rates thus determined can be used to assist. in prioritizing corrosion susceptible locations along a pipeline segment. and determining the re-inspection interval at. a given location. These field procedures are not developed for estimating pit or crack growth rates, if present, in the disbonded region.