Thermal Stability of Al2O3 Coatings on SUS 304 Stainless Steel

In order to assess the thermal stability of Al2O3 coatings of 0.2, 0.4 and 0.8μm thickness formed on SUS 304 stainless steel by ion plating, the specimens were annealed at 800-1000K for 1ks in a vacuum. The assessment was carried out by SEM observation and polarisation curves obtained in an aqueous solution of 0.5kmol m-3 H2SO4. The annealing at 800K does not cause mechanical defects in the coatings, while that at 1000K results in small cracks in the coatings and accordingly increases the current density nearly to the value for the uncoated specimen.