Effect of cathodic potentials on the SCC behavior of E690 steel in simulated seawater

Slow strain rate tensile tests, combined with fracture morphology observation and electrochemical measurements, were conducted to investigate the SCC behavior of E690 steel in simulated seawater at open circuit potential (OCP) and various cathodic potentials. Results showed that E690 steel had a certain degree of SCC susceptibility at OCP in simulated seawater and had a high susceptibility to hydrogen embrittlement (HE) at high cathodic potentials. The SCC susceptibility showed a distinct decline at −850 mVSCE because of the inhibition of the anodic dissolution, and the fracture surface exhibited a ductile failure of dimple. The SCC susceptibility presented a remarkable increase at −950 mVSCE with a distinct feature of brittle rupture and increased drastically as the potential became more negative. The bainitic lath boundaries had an opposite effect on the SCC behaviors of E690 steel. The fracture modes at OCP and various cathodic potentials were all transgranular cracking.