Effect of tensile stress in elastic and plastic range on hydrogen permeation of high-strength steel in sour environment

The new hydrogen permeation technique developed for the electrochemical permeation method makes it possible to evaluate the effect of applied tensile stress in both elastic and plastic range on hydrogen permeation behavior in high-strength steels. This study suggests that the iron sulfide film acts as sites for hydrogen reduction reaction and that the applied elastic stress weakens the stability of the sulfide film due to lots of cracks forming in the local sulfur deficient region, resulting in increase in both the anodic dissolution and hydrogen reduction reaction. In addition, the effect of applied stress in plastic range on hydrogen permeation behavior was clearly evaluated by excluding other side effects such as the reduced rate of hydrogen oxidation caused by the disruption of the Pd layer under stress. Furthermore, by evaluating hydrogen permeation behavior in the transient range from elastic to plastic stress, the effect of newly generated dislocation on the permeation current was accurately investigated without any side effect.