CORROSION-RESISTANT COATINGS (AL2O3) PRODUCED BY METAL-ORGANIC CHEMICAL-VAPOR-DEPOSITION USING ALUMINUM-TRI-SEC-BUTOXIDE

The metal organic chemical vapour deposition (MOCVD) of amorphous alum ina films on steel was performed in nitrogen at atmospheric pressure. This MOCVD process is based on the thermal decomposition of aluminium- tri-sec-butoxide (ATSB). The effect of the deposition temperature (wit hin the range 290-420-degrees-C), the precursor vapour pressure (5.33 x 10(-3)-2.67 x 10(-2) kPa), and the gas flow (6.5-12.51 min-1) of the MOCVD process have been studied in relation to corrosion properties a t high temperatures. The corrosion experiments were performed at 450-d egrees-C in a gas atmosphere containing 1% H2S, 1% H2O, 19% H-2, and b alanced Ar. It was found that the amount of corrosion products on an a lumina film (0.20 +/- 0.05 mg cm-2)-AISI 304 combination decreased wit h increasing deposition temperature of the coating. This was more pron ounced for the products formed through the coating owing to a certain porosity. The crack density, where products were also formed, was almo st unaffected.