Effects of cathodic polarization on corrosion fatigue life of E690 steel in simulated seawater

Effects of cathodic polarization on corrosion fatigue life of E690 steel in simulated seawater were studied by carried out electrochemical measurements and corrosion fatigue tests under different cathodic potentials. The results show that effects of cathodic polarization on corrosion fatigue life are different with different stress levels. When the peak stress is far below the proof stress (<0.8 σp0.2), the corrosion fatigue life increases with decreasing cathodic potential and reaches close to the fatigue life in air after −900 mV. However, when the peak stress is close to or beyond the proof stress (≥0.95 σp0.2), the corrosion fatigue life shows an trend of first increase and then decrease with decreasing cathodic potential and peaks at −850 mV. It is attributed to the synergistic effect between plastic deformation and hydrogen, which can be explained with hydrogen-promoting-plastic-deformation (HPPD) theory. Both anodic dissolution and HPPD can promote intergranular cracking. However, HPPD will not occur when the peak stress is far below the proof stress.