Abstract
Cathodic protection and external coating have been recognized as perhaps the most reliable and cost-effective means of controlling corrosion for pipelines. Each structure or piping system that is provided cathodic protection must be tested periodically to determine the effectiveness of the cathodic protection system. Pipe-to-soil potential measurements are recorded to determine the potential of a pipeline with respect to a reference electrode. Additionally, potential measurements are recorded in corrosion evaluations as a qualitative method to identify corrosion activity.
When properly interpreted and correlated with other measurements, pipe-to-soil potentials can: indicate the severity of both galvanic and electrolytic corrosion cells, as well as the level of cathodic protection in accordance with industry standard criteria. There are various challenges associated with pipeline potential readings with AC mitigation collocated with AC corridor. These challenges require alternative potential evaluation approaches for pipeline integrity evaluation.
The effect of AC Mitigation and corrective actions were studied over few years of research. Different techniques and multiple surveys conducted were utilized to develop a technique to correct the effect of AC mitigation as an external current source on potential measurements.
During the period of research, it was determined that the capacitive effect of the AC mitigation system causes significant errors in potential measurements. The capacitive effect of AC mitigation (capacitive error) would cause more negative potential measurements on the pipelines. The goal of this paper is to detail an alternative potential survey evaluation technique on a pipeline with an active AC mitigation system.
