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In-situ electrochemical impedance measurements of corroding stainless steel in high subcritical and supercritical water


The traditional method of corrosion studies of structural materials exposed to water at high pressures and temperatures is ex-situ weight gain/loss estimation and analyses of the oxide scales. In this work, in-situ electrochemical impedance spectroscopy (EIS) is applied to study behaviour of 316 L stainless steel exposed to sub-critical and super-critical water (SCW) with the aim to investigate the effect of temperature, in particular close to the critical point of water. As the second objective, the effect of exposure time during the long-term exposure at 500 °C was investigated. Impedance data were analyzed and discussed, based on changes in the physical and chemical properties of water. Instantaneous corrosion rate data, estimated from impedance data, were converted in weight differences and compared with the literature data available for 316 L steel corrosion in SCW. The good agreement obtained supports applicability of in-situ EIS for corrosion studies in super-critical range.