Effect of Hydrogen Charging on the Stress Corrosion Cracking Behavior of X70 Steel in Simulated Deep Seawater Environment

The effects of hydrogen charging on the electrochemical and stress corrosion cracking (SCC) behavior of X70 steel in a simulated deep seawater environment were investigated by using electrochemical measurements, slow strain rate tensile (SSRT) tests, and corrosion morphology characterization through SEM. The results showed that the concentrations of the adsorbed hydrogen in X70 steel after precharging under different hydrostatic pressures increased gradually and tended to be steady with the charging time. High hydrostatic pressures promoted the hydrogen permeation of X70 pipeline steel by promoting the permeating rate and quantity. The SCC susceptibility of X70 steel decreased first and then increased with the hydrogen-charging current density. The area reduction loss (Iψ) and true strain loss (Iε) exhibited the lowest SCC susceptibility at the 25 mA/cm2 hydrogen-precharging current density. The elongation rate loss (Iδ) exhibited the lowest SCC susceptibility at the 50 mA/cm2 hydrogen-precharging current density.