New findings on the factors accelerating AC corrosion of buried pipeline

• We model the interaction of different coating holidays under AC interference.
• AC current can provoke induced DC current between two holidays of different area.
• Induced DC current increases the corrosion rate of smaller holiday.
• Induced DC current and irreversibility of anodic reaction result in AC corrosion.

To simulate the interaction between different coating holidays on buried pipeline under alternating current (AC) interference, laboratory experiments were carried out using a specially designed circuit connecting two specimens of different sizes. The application of AC between two different specimens could induce DC current from the smaller specimen to the bigger one in the solution, which would increase the corrosion rate of the smaller specimen. The research showed that size difference between holidays on buried pipeline is an important factor in accelerating AC corrosion.