Coating of titanium carbide films on stainless steel by chemical vapour deposition and their corrosion behaviour in a Br₂-O₂-Ar atmosphere

Stainless steel (SUS304) plates were coated with TiC films using chemical vapour deposition (CVD) as a candidate material for “UT-3” which is a promising process of hydrogen production through the thermal decomposition of water. The corrosion behaviour of the TiC film-coated SUS304 plates was examined in a Br₂-O₂-Ar atmosphere. The effects of CVD conditions on the surface texture, deposition rates and preferred orientation of the TiC films were investigated, and the optimum CVD conditions determined. Corrosion of the TiC film-coated SUS304 plates in the Br₂-O₂-Ar atmosphere was mainly caused by oxidation of the TiC film and SUS304 substrate. Microcracks in the TiC films lead to corrosion of the SUS304 substrate. At oxygen partial pressures below 0.1 kPa, weight loss was observed due to the formation of volatile titanium and iron bromides. At oxygen partial pressures greater 0.1 kPa, the time dependence of weight increase was parabolic due to the formation of oxide scale. The oxide scales were mixtures of TiO₂, Fe₂O₃ and Fe₃O₄. The corrosion mechanism is discussed thermodynamically.