The evolution of electrochemical behaviour and oxide film properties of 304 stainless steel in high temperature aqueous environment

The evolution of electrochemical behaviour and oxide film properties of 304 stainless steel in high temperature aqueous environment have been studied by polarization curves, electrochemical impedance spectra (EIS) and X-ray photoelectron spectroscopy (XPS). The electrochemical data indicate that the corrosion resistance of the steel increases with immersion time. The EIS and XPS analyses show that the oxide films are a duplex structure and the corrosion rate is dominated mainly by the Cr-rich inner layer. The correlation between the evolution of the electrochemical behaviour and the changes of the oxide film properties is discussed.

► Both of the EIS data and XPS data indicate the oxide film has a duplex structure.
► The resistance of the inner layer increases faster than that of the outer layer.
► The currents for oxide formation are controlled by different mechanisms.