2002 Volume 51 Issue 5 Pages 221-226
It has well been recognized that buried steel pipelines can be effectively protected against corrosion by the combined use of high resistivity coatings and cathodic protection (CP). Pipe-to-soil potential survey has been conducted periodically to evaluate the CP levels. Recently the risks such as AC corrosion, overprotection and corrosion inside casing pipes are increasing due to changes in burial situations, application of new construction techniques and so on. It is effective to measure DC and AC current densities using probes for the appropriate assessment of those risks. New CP criteria based on DC and AC current densities measured using probes have been developed in order to eliminate the risks such as AC corrosion, overprotection and corrosion inside casings.