Synergistic Effects of Hydrogen and Stress on Corrosion of X100 Pipeline Steel in a Near-Neutral pH Solution

In this work, scanning vibrating electrode technique and local electrochemical impedance spectroscopy measurements were used to investigate the effects of stress and hydrogen on electrochemical corrosion behavior of a X100 pipeline steel in a near-neutral pH solution. The stress distribution on the test specimen was calculated using the finite element method. Results demonstrated that the hydrogen-charging enhances the local anodic dissolution of the steel, contributing to the formation of a layer of corrosion product. However, there is little difference of the charge-transfer resistance between the regions with and without hydrogen-charging due to rapid diffusion of hydrogen atoms throughout the specimen with time. When the local stress concentration is not significant enough to approach the yielding strength of the steel, the steel is still in a relatively stable state, and there is a uniform distribution of dissolution rate over the whole surface of the steel specimen. Although the stress-enhanced activation is not sufficient to result in an apparent difference of current density of the steel, the activation of the steel would activate dislocations, which serve as effective traps to the charged hydrogen atoms. With the increase of hydrogen concentration, the hydrogen-enhanced anodic dissolution becomes dominant.