Effect of hydrostatic pressure on hydrogen behavior on the surface of X70 pipeline steel

Hydrogen embrittlement is a serious phenomenon resulting in severe ductility deterioration of engineering materials due to the presence of hydrogen atoms. The low concentration of dissolved oxygen in deep-sea provide the condition for hydrogen production. Herein, the hydrogen permeation behavior in X70 pipeline steel in acid/alkaline environment under different hydrostatic pressure were investigated via electrochemical hydrogen permeation parameters. The results revealed the different trends of i∞ with increasing hydrostatic pressure. The phenomenon was described from the perspectives of hydrogen generation, absorption/desorption and permeation process by potentiodynamic polarization, linear sweep voltammetry (LSV) and EIS tests. The experimental permeation data were fitted with surface effect model and leads to the conclusion that the hydrostatic pressure greatly enhanced the adsorption rate and restricts the desorption rate of absorbed hydrogen atoms on the metal surface, thereby the process of atomic hydrogen compounding into hydrogen molecules is inhibited, leading to an increase in sub-surface hydrogen concentration (C0).