Cailiao Baohu (Apr 2023)
Effect of Zinc and Aluminum Ions on the Properties of the Oxide Film Formed on 304L Stainless Steel in High Temperature Water
Abstract
To clarify the corrosion mechanism of 304L stainless steel in the first circuit of nuclear power plant，304L stainless steel was immersed in a solution simulating the water environment in the first circuit of nuclear power plant which contained different concentrations of zinc and aluminum ions for 168 hours at 290 ℃to form an oxide film on its surface.Then，the resulting oxide film was tested by means of potentiodynamic scanning，AC impedance spectrum test，Mott-Schottky curve test and photo-electrochemical test，and the polarization curves，electrochemical parameters，semiconductor type，flat band potential，carrier concentration，band gap potential and phase composition of the oxide film were obtained.Results showed that the simultaneous addition of zinc and aluminum ions could significantly reduce the corrosion rate of 304L stainless steel.When the concentration of Zn ion was 40 μg/L and the concentration of Al ion was 90 μg/L，the corrosion current density of the oxide film formed on the surface of 304L stainless steel was the smallest，and the corrosion resistance of the oxide film was the best.Compared to the oxide film formed with the injection of zinc ion alone into the first circuit of a nuclear power plant，the film on the surface of 304L stainless steel showed a double-layer structure，its semiconductor type was n-type，the flat band potential shifted negatively，and the carrier concentration decreased.Compared to the oxide film formed without the addition of zinc and aluminum ions，two more phases of ZnAl2O4 and α-FeOOH emerged in the phase composition of the oxide film.Therefore，adding zinc and aluminum ions to the simulated solution under high-temperature and high-pressure conditions could effectively increase the corrosion resistance of 304L stainless steel.
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