Effect of hydrogen on the pitting corrosion of 2205 duplex stainless steel welded joints

The effect of hydrogen on the pitting susceptibility of 2205 duplex stainless steel welded joints was investigated using metallographic characterisation, electrochemical techniques and immersion experiments. The results show that the diffusible hydrogen content in the welded joints is approximately twice that of base material (BM). Hydrogen significantly decreases the pitting potential (Epit) of the welded joints, while increasing the carrier density in the passive film, suggesting that hydrogen weakens the protective properties of the passive film and increases the pitting susceptibility of the welded joints. According to immersion experiments, the pitting susceptibility of the welded joint from high to low is heat-affected zone (HAZ), BM and weld metal (WM), the HAZ tends to be more prone to the formation of larger and more stable pits, and the number of inclusions at the HAZ is significantly greater than that at the BM and WM. For BM under hydrogen charging, austenite phase is usually corroded first, because hydrogen tends to be enriched in the austenitic phase of BM. However, in some regions of WM, ferrite phase corroded first, which is related to the enrichment of hydrogen in the ferrite in the weld area.