Effects of cathodic polarisation on hydrogen embrittlement susceptibility of X70 steel in low temperature and low dissolved oxygen seawater

摘要

The hydrogen induced cracking of X70 pipeline steel was investigated in low temperature and low dissolved oxygen seawater (4℃ and 3-4 mg L~(-1) dissolved oxygen) by potentiodynamic polarisation, slow strain rate tests and hydrogen permeation measurements. The results showed that the hydrogen evolution potential of X70 steel in low temperature and low dissolved oxygen seawater decreased compared with the normal shallow seawater. The susceptibility to hydrogen embrittlement increased as the potential shifted in the negative direction. When the polarisation potentials were below -1050 mV(SCE) in low temperature and low dissolved oxygen seawater, the fracture surfaces exhibited quasi-cleavage fracture.