Abstract
On the basis of the field research on AC corrosion by induced AC voltage on a cathodically protected pipeline in soil paralleling electric power transmission line, laboratory study was performed with a carbon steel specimen simulating a coating defect to understand the effect of superimposed AC current at 50 Hz of the power-line frequency on corrosion. Results have demonstrated that the occurrence of severe corrosion as high as 6.5mm/y was obtained under applied AC current density of 19 mA/cm2 without DC current imposition. On the other hand, corrosion rates decreased with an increase of DC current densities suggesting effectiveness of catholic protection to suppress AC corrosion. For aiming at the final goal to establish cathodic protection criteria with induced AC voltage, the quantitative relationship among corrosion rate, AC current density, and DC current density has been examined.
