Some cathodic protected pipelines installed along high voltage transmission lines have been presenting corrosion problems. The causes of this corrosion have been attributed to alternating current (AC) interferences coming from high voltage transmission lines and/or from electric supplying systems. There are several criteria adopted by literature to evaluate the probability of AC corrosion. However, these criteria are contradictory and inefficient, since failures due to AC corrosion have occurred in pipelines which presented electric and electrochemical parameters within the acceptable limits of those criteria. Moreover, there is no consensus regarding the mechanisms of AC corrosion. The present work has an objective to understand the mechanisms of AC corrosion and to suggest field measurement methodologies for evaluating the levels of AC interferences in pipelines, as well as to establish a thermodynamic criterion for assessment of the probability of AC corrosion occurrence in pipelines.

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