Application of electrochemical techniques in investigation of the role of hydrogen in near-neutral pH stress corrosion cracking of pipelines

It has been acknowledged that hydrogen plays a critical role in near-neutral pH stress corrosion cracking (SCC) of pipelines. However, the accurate mechanism for hydrogen involvement remains unknown. This work reviewed the applications of various electrochemical techniques towards understanding near-neutral pH SCC. The techniques reviewed include electrochemical hydrogen permeation, cyclic voltammetry, electrochemical impedance spectroscopy, electrochemical noise and scanning photo-electrochemical microscopy. The manner by which these techniques allow for the investigation of the hydrogen evolution mechanism, adsorption/desorption and permeation kinetics and hydrogen diffusion and accumulation in steel as well as the interactions between hydrogen, anodic dissolution and stress at crack tip in near-neutral pH environmental condition is described. It is anticipated that the advanced electrochemical measurement techniques provide essential tools to investigate the mechanistic aspects on hydrogen involvement in near-neutral pH stress corrosion cracking in pipelines.