AL2O3 COATINGS AGAINST HIGH-TEMPERATURE CORROSION DEPOSITED BY METAL-ORGANIC LOW-PRESSURE CHEMICAL-VAPOR-DEPOSITION

Metal-organic chemical vapour deposition of thin amorphous films of Al2O3 on steels was performed at low pressure. Aluminium tri-sec-butoxide (ATSB) was used as a precursor. The effects of the deposition temperature (200-380 degrees C), the deposition pressure (0.17-1.20 kPa) and the ATSB concentration ((5.5-33.5) x 10(-4) kPa) were studied with respect to the growth rate of the coating and the sulphidation properties at high temperatures. The sulphidation experiments were performed for 70 h at 450 degrees C in a gas atmosphere consisting of 1% H2S, 1.5% H2O, 19% H-2, Ar balance. From the results and scanning electron microscopy observations the best process conditions were determined.