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 area differences between holidays on the pipeline are important in accelerating corrosion with AC current, which would provoke the induced DC current between two linked specimens of different areas. The induced DC current became anodic current on smaller specimen and cathodic current on the bigger one, resulting in acceleration of corrosion rate of bigger specimen and deceleration of smaller ones. Furthermore, as the area difference became larger, the corrosion rate of smaller holiday was also higher. Upon application of AC current, corrosion potential of both two specimens shifted negatively. The induced DC current was larger with the increase in the corrosion potential difference between the two specimens in the presence of AC current. Corrosion caused by AC current includes two parts, namely the one caused by the induced DC current between two specimens and the other caused by irreversibility of anodic reaction.
New findings on the factors accelerating AC corrosion of buried pipeline
Neue Erkenntnisse zu den Beschleunigungsfaktoren der Wechselstromkorrosion von unterirdischen Pipelines
Corrosion Science ; 81 ; 1-10
2014
10 Seiten, 14 Bilder, 35 Quellen
Article (Journal)
English