Mechanistic aspect of near-neutral pH stress corrosion cracking of pipelines under cathodic polarization

This paper investigates mechanistically stress corrosion cracking (SCC) of an X70 pipeline steel that is under cathodic protection (CP) in a near-neutral pH solution. It was found that there is a critical potential range, i.e., −730 and −920 mVSCE, where the steel is in a non-equilibrium electrochemical state, and anodic dissolution (AD) reaction may occur when the steel is polarized cathodically. When the applied potential is more positive than this range, SCC is AD-based; while the applied potential is more negative, SCC of pipelines is under hydrogen embrittlement (HE) mechanism. When the polarization potential is within the range, SCC of the steel is under the combined effect of AD and HE. Therefore, AD may still occur on pipeline steel that is under CP with the potential within this critical range, contributing to the cracking process.

► Stress corrosion cracking of pipelines under cathodic polarization is modeled.
► The roles of dissolution and hydrogen embrittlement in pipeline SCC are determined.
► SCC of pipeline under cathodic protection is illustrated mechanistically.