Hydrogen Diffusion Behavior of Mooring Chain Steel under Stress

The diffusion behavior of hydrogen in mooring chain steel at different stress levels was studied using electrochemical hydrogen charging method combined with constant stress tensile device. The results show that anodic current density was stable after reaching the maximum value when the specimen was charged with hydrogen under stress-free condition. When the specimen was deformed under stress, the anodic current density displayed different trends. Under elastic stress, the anodic current density increased slightly, the apparent diffusion coefficient of hydrogen decreased a little, and meanwhile the penetration needed somewhat long time, compared with stress-free condition. Under yield stress both the anodic current density and the apparent diffusion coefficient of hydrogen reached the maximum, and the penetration time was minimized. But with the increase of loading time, both anodic current density and apparent diffusion coefficient of hydrogen decreased apparently, and the penetration time prolonged. Under the stress beyond yield strength, the anodic current density returned to the value under stress-free or elastic stress, the diffusion coefficient of hydrogen decreased, and the hydrogen needed more time to penetrate.