Hyunsoo Kim, Noboru Akao,Nobuyoshi Hara and Katsuhisa Sugimoto
Department of Metallurgy, Faculty of Engineering, Tohoku University, Sendai
Thin Fe2O3-TiO2 films were formed on Pt by a low pressure MOCVD technique and their corrosion resistance was examined in HCl and H2SO4 solutions by immersion tests, dynamic polarization tests, and in-situ ellipsometry under potentiostatic polarization. In the immersion tests, dissolution rate of the films was determined by ellipsometry.
The dissolution rate of the films in 5 kmol⋅m-3 HCl decreased with increasing cationic fraction of Ti4+ ions, XTi, in the films and formation temperatures of the films. When the value of XTi exceeded 0.32, the films formed at 673 K did not dissolve in 5 kmol⋅m-3 HCl and showed exellent corrosion resistance.
The films did not dissolve in 1 kmol⋅m-3 H2SO4 under anodic polarization, but dissolved owing to the cathodic reduction of Fe2O3 under cathodic polarization. The dissolution rate of the films under cathodic polarization decreased with an increase in potential and also in the cationic fraction of Ti4+ ions, XTi, in the films.
(Received January 31, 1996)
Fe2O3-TiO2 film, low pressure MOCVD technique, corrosion resistance, immersion test, dynamic polarization test, in-situ ellipsometry, potentiostatic polarization, dissolution rate, cathodic reduction
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