THE EFFECT OF CHLORINE ON THE HIGH-TEMPERATURE CORROSION OF SIO2-COATED INCOLOY 800H

The effect of chlorine in coal gasification atmospheres was investigated on the high temperature corrosion of Incoloy 800H coated with SiO2. The experiments were performed in a representative gas mixture between 450 and 750-degrees-C. The weight gain in this environment was significantly decreased with coating thicknesses to about 1.4 mum. Larger thicknesses led to an increased corrosion attack. The coating contained small cracks filled with iron-nickel sulphides. Probably, pre-existing cracks in the SiO2-coating due to internal stresses, were responsible for this behaviour of the coating. With increasing temperature or p(Cl2), the corrosion rate increased. The mechanism of the chlorine-induced corrosion is unclear as yet.