Effect of Cathodic Polarization Potential on Hydrogen Induced Stress Cracking of Duplex Stainless Steel

Hydrogen induced stress cracking (HISC) has sometimes been experienced when duplex stainless steels are applied as subsea facilities under cathodic protection (CP). The effects of cathodic potential on HISC of duplex stainless steel were studied by electrochemical methods, slow strain rate tensile test (SSRT) and four-point bending test. At the constant potential, with the hydrogen evaluation reaction proceeding, OH- on the surface of metals increases and the calcium and magnesium deposition layer can decrease the current to a static value. The SSRT results show that the fracture mode changed from ductile to brittle when the duplex stainless steel was polarized to -1.05V (SCE) or more negative potential. The four-point bending test results show the relationship between potential and the sensitivity of HISC in artificial seawater at 3°C when the specimens were loaded up to 98% of yield stress (R_p0.2). The hydrogen concentration of the specimens was also measured and the occurrence of HISC needs a certain hydrogen concentration.