Effects of Dissolved Gas and Cold Work on the Electrochemical Behaviors of 304 Stainless Steel in Simulated PWR Primary Water

The effects of dissolved gas and cold work on the electrochemical behaviors of Type 304 stainless steel were investigated in simulated pressurized water reactor primary water environment by potentiodynamic polarization and electrochemical impedance spectroscopy. Results reveal that both dissolved gas and cold work have a significant influence on anodic passivation properties and corrosion resistance of the oxide film. In Ar deaerated water and oxygenated water environments, the corrosion potential of stainless steel and Pt is controlled by the dissolved oxygen concentration, and the corrosion resistance of the inner barrier layer is much higher. However, in H₂ deaerated water, the corrosion potential is depressed by the H₂/H₂O redox potential and the inner oxide film formed in H₂ deaerated water is less stable. In addition, the passive region of polarization curves on 304 stainless steel in oxygenated and Ar deaerated water is controlled by metal dissolution instead of water oxidation, and the passive current of the 304 stainless steel in H₂ is about two times higher than that in Ar. Conversely, the anodic current density on polarization curves is controlled by the O₂ and water oxidation instead of metal dissolution because the compact and thick oxide films have already been formed. The cold work deformation can accelerate general corrosion of the 304 stainless steel, and both active dissolution current and passivated current increase linearly with the increase of the content of martensite induced by cold deformation.