In-Situ Electrochemical Impedance Measurement of Oxide Film Formed on Type 304 Stainless Steel in High-Temperature Water Available to Purchase

Electrical resistivity of the oxide film formed on Type 304 (UNS S30400) stainless steel (SS) in 288°C water containing various oxygen (O₂) and hydrogen peroxide (H₂O₂) concentrations was evaluated by in-situ electrochemical impedance and anodic polarization measurements. Higher electrochemical corrosion potentials (ECP) were measured in the presence of H₂O₂, as compared to the ECP value measured at the same level of O₂. It also was clear that the polarization resistance decreased with increases in ECP and H₂O₂ concentration. However, a more significant decrease in polarization resistance was measured when H₂O₂ was present in the water at a given ECP. This impedance data showed the important role of the water chemistry on the degree of oxide resistance. In addition, the polarization resistance result indicated that the oxide film formed on Type 304 SS in 288°C water containing H₂O₂ could be less resistance and consequently more susceptible to environmentally assisted cracking.