High-Temperature Electrochemical Corrosion Behavior of Fe-Cr-Ni Alloys in Simulated Pressurized Water Reactor Water

The electrochemical corrosion behavior of Cr, Ni, and Mo in Fe-Cr-Ni alloys in simulated pressurized water reactor water was investigated by thermodynamic calculation, potentiodynamic polarization, and electrochemical impedance spectra analysis. The results revealed that the corrosion potential of Fe-Cr-Ni alloys in Ar-deaerated water was between the and , affected most by the Fe anodic dissolution and water reduction. The oxidation current for Fe3O4 to Fe2O3 can be only detected when the potential crosses the Fe3O4/Fe2O3 phase boundary during potentiodynamic polarization. For both stainless steels and nickel-based alloys, rapid chromium oxide dissolution may be an important reason for the short stress corrosion cracking (SCC) initiation times and higher SCC susceptibility measured in oxygenated pure water. Mo and Cr additions in Fe-Cr-Ni alloys reduce the general corrosion rate of stainless steels in the passive region, but no effect is observed in the transpassive region where chromium oxide is dissolving. Mo may stabilize the inner compact Cr/Ni-rich layer oxides of Mo-containing stainless steels.