Comparison of corrosion resistances between Fe₂O₃-TiO₂ artificial passivation film and passivation film on Fe-Ti alloy

Fe₂O₃-TiO₂ double-oxide films were formed on Pt substrates by low-pressure metallorganic chemical vapor deposition using iron acetylacetonate and tetraisopropoxytitanium as precursors and O₂ as a reaction gas. Fe-Ti alloys were fabricated by an ion-beam sputter and an arc-melting process. The corrosion resistances of the Fe₂O₃-TiO₂ films and the Fe-Ti alloys were examined in acid solutions. The thinning rate of the Fe₂O₃-TiO₂ films in 5 M HCl decreased with an increase in the formation temperature. Likewise, the dissolution rate decreased with increasing titanium cationic fraction in the films. The films hardly dissolved at anodic potentials, while significant dissolution occurred at cathodic potentials in 1 M H₂SO₄ owing to the selective reduction of iron oxide components in the films. Sputter-deposited Fe-Ti alloy films containing more than 39 atom % Ti and arc-melted Fe-Ti alloys containing more than 57 atom % Ti showed high corrosion resistance when passivated anodically in 5 M HCl. The dissolution rates of the Fe₂O₃-TiO₂ films in 5 M HCl appear to be significantly smaller than those of the passive films on the Fe-Ti alloy films and the Fe-Ti alloys in the same solution.