Both the titanium oxide, TiO2 and chromium oxide, Cr2O3 were deposited on aluminum substrate with alkoxid-CVD to improve the pitting corrosion resistance in neutral aqueous solution. Titanium tetrasopropoxide, Ti(C3H7O)4 and chromium acetylacetonate, Cr(C5H7O2)3 were employed as evaporation sources for TiO2 and Cr2O3, respectively. The deposition of oxides was performed at a deposition rate of about 60nmh-1 under controlled mass flow rates (200sccm and 500sccm) of nitrogen carrier gas at different substrate temperatures (373K to 573K for TiO2 and 703K for Cr2O3), and at different evaporation source temperatures (298K and 343K for TiO2 and 433K and 513K for Cr2O3). Particularly, for the deposition of Cr2O3, water vapor at 353K was added to nitrogen carrier gas to promote the deposition. The Auger analysis in depth indicated that aluminum of oxidation state is present in the interface layer between deposited oxide and aluminum substrate for both oxides. Furthermore, the ellipsometrical results suggested that the deposited oxides were amorphous. It was found that the average pitting potential of aluminum in pH 8.4 boric-borate solution containing 10-2mol dm-3 Cl- ions increased by 1.5V due to the surface coating of both oxides with thickness of 40nm.
