Effects of alternating current interference on cathodic protection potential and its effectiveness for corrosion protection of pipelines

Abstract

In this work, the effect of alternating current (AC) interference on cathodic protection (CP) potential on a X65 steel in a near-neutral pH bicarbonate solution was investigated, and the CP performance under AC was evaluated by weight-loss measurements. The CP potential applied on the steel cannot be maintained in the presence of AC interference. The shift of the CP potential depends on the applied CP level and AC current density. No matter if the direct current potential of the steel is shifted negatively or positively upon application of AC, the steel suffers from increased corrosion. The AC decreases the effectiveness of CP for corrosion protection. The CP standard at −0.850 V (copper sulphate electrode) that does not consider the AC interference is not appropriate for AC corrosion protection.

Keywords:

• Alternating current corrosion
• Cathodic protection
• Pipelines
• Direct current potential

Additional information

Funding

This work was supported by the University of Calgary.