Corrosion-Potential Fluctuations and Polarization Resistance Measurements in High-Subcritical and Supercritical Water Oxidation Environment Available to Purchase

The potential fluctuation (potential noise) of UNS30400 (type-304) stainless steel electrode was measured in a 1.04x10^-3mol/dm³ HCl solution at temperatures up to 380°C and pressure of 24MPa. The solution was saturated with pure O₂ gas at ambient temperature and atmospheric pressure. The polarization resistance and the polarization curve were also measured to investigate electrochemical reaction models under the conditions.

Random potential fluctuation occurred on corrosion potential at 360°C. The surface morphology of the used electrode showed that it had been subjected to intense general corrosion during the measurement. However, at 300°C, the RD-type potential fluctuation developed on the potential, and the electrode showed the traces of localized corrosion activity. At the temperatures below 250°C and at 380°C, no potential fluctuations were found, and essentially no corrosion traces were observed on the electrodes. The polarization curves suggested that the rate of corrosion reaction was controlled by that of the cathodic reaction at temperatures from 200 to 360°C. However, at 380°C, the curves suggested corrosion rate was controlled by the anodic reaction. At temperatures from 200 to 360°C, the corrosion currents estimated from the R_p values and the Tafel slopes showed good agreements with the limiting diffusion currents at each temperature.