Electrochemical behavior of nickel containing passive oxide films on carbon steel in alkaline medium

The passive oxide film formed on the carbon steel surface in lithiated water was modified by the incorporation of nickel ions by hydrothermal deposition at 250°C. The aim was to verify to what extent the in-situ oxide films grown in presence of nickel ions improved the corrosion resistance of the carbon steel substrate in comparison to the films formed in the absence of nickel ions at different exposure times. Grazing incidence-X-ray diffraction studies confirmed the formation of the spinel phase in the passive oxide film. X-ray photoelectron spectroscopy revealed the presence of the nickel ions in the oxide lattice. The electrochemical behavior of the oxide films formed on the carbon steel surface was studied using electrochemical impedance spectroscopy and potentiodynamic anodic polarization methods. Tafel plot extrapolations from the potentiodynamic anodic polarization plots revealed a substantial difference in the corrosion resistance of the films formed on carbon steel substrate in the presence of nickel ions. The oxides grown in the absence and in the presence of nickel ions exhibited similar corrosion current densities but showed a higher polarization resistance value in the presence of nickel ions. The semiconductor properties of these oxides were characterized by Mott Schottky measurements and the results are presented in detail in this paper.