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

The effect of chlorine in coal gasification atmospheres was investigat ed on the high temperature corrosion of Incoloy 800H coated with SiO2. The experiments were performed in a representative gas mixture betwee n 450 and 750-degrees-C. The weight gain in this environment was signi ficantly decreased with coating thicknesses to about 1.4 mum. Larger t hicknesses led to an increased corrosion attack. The coating contained small cracks filled with iron-nickel sulphides. Probably, pre-existin g cracks in the SiO2-coating due to internal stresses, were responsibl e for this behaviour of the coating. With increasing temperature or p( Cl2), the corrosion rate increased. The mechanism of the chlorine-indu ced corrosion is unclear as yet.