Derivation of the mechanistic relationship of pit initiation on pipelines resulting from cathodic protection potential fluctuations

Abstract

In this work, a square wave polarization (SWP) technique was used to simulate the cathodic protection (CP) potential fluctuations on an API X100 pipeline steel to investigate the effect of potential fluctuations on pit initiation. The derived numerical relationship between the potential of the double-charge layer at the steel/solution interface and the CP potential fluctuation is consistent with the testing results. When the upper potential of the SWP potential is shifted positively (or negatively) while the lower potential is fixed, the potential of the double-charge layer linearly increases (or decreases), causing the increase (or decrease) of the pit density.