THE EFFECT OF RARE-EARTHS DEPOSITED ON STEEL SURFACES, BY DIFFERENT PROCESSES (SOL-GEL, ELECTROPHORESIS, OMCVD), ON HIGH-TEMPERATURE CORROSION BEHAVIOR

In this paper, different methods of rare earth oxides deposition on the surface of AISI 304 steel are described: sol/gel, electrophoresis in aqueous or organic medium, OMCVD of rare earth beta-diketonates. After the deposition, all the samples were reheated. This treatment was absolutely essential for a strengthening effect of the protective oxide scale. Oxidation of coated and non-coated samples was performed under isothermal and cyclic conditions. The effect of rare earth deposition is significant in isothermal conditions. However, in thermal cyclic conditions, the effect of a rare earth deposited on surface is spectacular. Scale spallation is then completely avoided under the chosen experimental conditions. The adherence of the protective scale could be due to an inversion of the defect structure oxide as it has been suggested in literature, but no experimental evidence to support this can be put forward from this work.