Morio Ishikawa1 and Katsuhisa Sugimoto2
1Graduate Student, Tohoku University, Sendai
Single, duplex and quadruple layer films having the thickness between 20--300 nm of Al2O3, Cr2O3, TiO2 and their combinations were prepared on an Fe substrate by metalorganic chemical vapor deposition technique. Corrosion protection properties of these films were examined in 3 mass%NaCl, 1 kmol•m-3 H2SO4 and 1 kmol•m-3 NaOH by the measurement of electrochemical activation time. In the case of single layer films, the order of protection ability was Cr2O3>Al2O3>TiO2. The adhesiveness of Cr2O3, however, became poorer with increasing film thickness. Al2O3 films showed good adhesiveness at any film thickness examined. For duplex layer films, the order was Cr2O3 (upper)/Al2O3 (lower)>TiO2 (upper)/Al2O3 (lower)>Al2O3 (upper)/TiO2 (lower). The thickness of 40--50 nm of Cr2O3 layer was necessary to get higher corrosion resistance in the structure Cr2O3 (upper)/Al2O3 (lower), Much higher corrosion resistance was given by quadruple layer films of Cr2O3 (uppermost)/Al2O3/Cr2O3/Al2O3 (lowermost) . The uppermost layer of these films was also needed to be 40--50 nm thickness to get the best resistance. The corrosion resistance of the quadruple films was higher than that of passive films on SUS304 and SUS430 stainless steels.
metalorganic chemical vapor deposition, thin films, oxide coating on iron, mutiple layers, corrosion protection, aqueous solutions
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