Improvement in corrosion resistance of the 316L stainless steel by means of Al2O3 coatings deposited by the sol-gel method

Two-, four- and six-layer Al2O3 coatings of the AISI 316 type stainless steel have been prepared by means of the sol-gel method. As a precursor substance aluminium isopropoxide was used. The coatings were approx. 2-3 μm thick and had amorphous structures. The higher sintering temperature (within the range 500-85 C), the lower cathode current density values, however also the lower breakdown potentials. Basing on results of EIS measurements it has been determined that the stainless steel/Al2O3 coating system may be substituted by an electrical model comprising three constant phase elements. The aluminium oxide coating heated at temperature of 500 C remains stable within the period of 1000 hours exposition in the Ringer's solution. (orig.)