Micro-Electrochemical Characterization of the Synergism of Hydrogen and Stress in Anodic Dissolution of Steel and Its Implication on Pipeline Stress Corrosion Cracking

Localized electrochemical impedance spectroscopy (LEIS) technique was used to investigate the effects of stress and hydrogen as well as their synergism on anodic dissolution of steel under near-neutral pH condition where pipeline stress corrosion cracking (SCC) has been reported. There exists a threshold stress value, under which there is little effect of applied stress on anodic dissolution of steel. Above the value, the dissolution rate of steel increases with the stress. Hydrogen-charging enhances anodic dissolution of steel, which is attributed to the effect of hydrogen on the formation of corrosion product layer and the activation of the steel. The stress effect factor and the stress-hydrogen synergism effect factor are quantified. A detailed analysis shows that the synergism of stress and hydrogen at crack tip is expected to play an important role in near-neutral pH SCC of pipelines.