Corrosion resistance of artificial passivation films of Fe[sub 2]O[sub 3]-Cr[sub 2]O[sub 3]-NiO formed by metalorganic chemical vapor deposition

A series of thin Fe[sub 2]O[sub 3]-Cr[sub 2]O[sub 3]-NiO films were formed on Pt by an MOCVD technique using Fe(III), Cr(III), and Ni(II) acetylacetonate. The corrosion resistance of the films was examined in H[sub 2]SO[sub 4] and HCl by measuring the film thickness using ellipsometry and the chemical analysis of test solutions with ICPS. The dissolution rate of Fe[sub 2]O[sub 3]-Cr[sub 2]O[sub 3] composite films decreases exponentially with an increase in the cationic mass fraction of Cr[sup 3+] ions, X[sub Cr], of the films, and at the values of X[sub Cr] larger than 0.7 it becomes two orders of magnitude lower than that of Fe[sub 2]O[sub 3] films. The same type of changes in the dissolution rate with X[sub Cr] was observed for the NiO-Cr[sub 2]O[sub 3] composite films. Therefore, the addition of Cr[sub 2]O[sub 3] to Fe[sub 2]O[sub 3] and NiO films effectively improves the corrosion resistance. The addition of NiO to Fe[sub 2]O[sub 3]-Cr[sub 2]O[sub 3] composite films containing an adequate amount of Cr[sub 2]O[sub 3] does not bring an effective improvement in corrosion resistance. Therefore, the corrosion resistance of Fe[sub 2]O[sub 3]-Cr[sub 2]O[sub 3]-NiO composite films is determined primarily by the Cr[sub 2]O[sub 3] content of the films.