Fe2O3-Cr2O3 artificial passivation films were formed on Pt substrates by low pressure metallorganic chemical vapor deposition technique using iron(III) acetylacetonate [Fe(O2C5H7)3] and chromium(III) acetylacetonate [Cr(O2C5H7)3] as precursors at substrate temperatures of 150-350 °C. Relationships between the crystal structure, and also the chemical state of constituent elements, and the corrosion resistance were examined on the films in acid solutions. The films deposited above 300 °C had crystalline structures, and those deposited below 250 °C had amorphous structures. The films deposited above 250 °C had a high amount of M-O-type chemical bonds, and those deposited below 200 °C had a high amount of M-OH-type chemical bonds. The films deposited above 300 °C hardly dissolved in 1.0 M HCl and those deposited below 250 °C, however, easily dissolved in the solution. The dissolution rate of the films in the solution increased with decreasing substrate temperature. Passive and transpassive current densities of the films in 1.0 M H2SO4 were dependent on the substrate temperature and increased with decreasing the temperature. When polarized cathodically in 1.0 M H2SO4 and 0.5 M HCl, the films deposited below 250 °C dissolved due to the reduction of the Fe2O3 component in the films. The reduction of Fe2O3 component was, however, suppressed on the films deposited above 300 °C. Therefore, with increasing crystallinity and amount of M-O-type chemical bonds, the corrosion resistance of the films increases in HCl and H2SO4 solutions.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry