Corrosion behavior and electrochemical properties of heat-treated Fe-20Cr-18Ni-6Mo-0.8Cu-0.2N-La alloys in alkaline seawater

Abstract This study examines the microstructure, corrosion resistance, and electrochemical behavior of Fe–20Cr–18Ni–6Mo–0.8Cu–0.2N–La alloys after heat treatment at different temperatures. The results show that heating the alloy to 1200 °C for 1 h leads to the dissolution of second-phase particles, and the undissolved precipitation is Mo-rich phase σ-FeCrMo. Loss-in-weight analysis indicates that corrosion resistance is better at 75 °C than at 50 °C, with the 0.5 wt% alloy showing the lowest corrosion rate (75 °C: 0.0116 mm/a). Electrochemical tests indicate the 0.5 wt% La alloy shows the lowest corrosion current densities of 5.272 × 10 −7 A/cm 2 at 50 °C and 1.183 × 10 −6 A/cm 2 at 75 °C, demonstrating superior corrosion resistance as a cathode. Surface roughness analysis shows that the surface roughness is decreased after alkaline seawater (ASW) corrosion at 75 °C. This study highlights the potential of austenitic stainless steels as cathode materials for hydrogen (H 2 ) production from seawater electrolysis (SWE).