Investigating the effect of heat treatment on hydrogen permeation behavior of API X-70 steel

Pipeline steels absorb different amounts of hydrogen during transportation of sour oil and gas. Since hydrogen-related damages such as hydrogen-induced cracking are strongly affected by hydrogen permeation behavior of steels, the purpose of this study determined to investigate hydrogen permeation behavior in API X-70 pipeline steel using electrochemical permeation method. The effect of heat treatment was also considered. It was found that hydrogen diffusivity increased by annealing the X-70 and it was decreased by normalizing. The condition was reverse for hydrogen apparent solubility. Finally, it was concluded that change in hydrogen diffusivity can be attributed to changes in grain size due to heat treatment.