Evaluation of AC Corrosion in Pipelines Buried Using an AC Probe

Corrosion by alternating current in buried pipelines has been investigated for several years since the first AC-induced corrosion failure in the 60’s. After this occurrence, many research groups have been studied the phenomena in order to understand the mechanism and to purpose reliable criteria to access the probability of AC-induced corrosion in buried pipelines. However, the proposed criteria  are contradictory and inefficient because they consider the influence of direct and alternating stray currents separately. In order to purpose a reliable criterion for AC-induced corrosion, it is necessary to consider the coupling between DC and AC currents. Thus, the field measurements should give information about the level of AC interference, the cathodic protection potential, the level of the DC and AC potential coupling and all this measurements must be carried out without the IR-drop influence. This work has as an objective to describe a new technique developed to verify the thermodynamic probability of AC-induced corrosion. Field results obtained through the described new technique are presented and discussed.