ACTIVE CORROSION OF SINTERED ALPHA-SILICON CARBIDE IN OXYGEN CHLORINE GASES AT ELEVATED-TEMPERATURES

The active corrosion of sintered α‐silicon carbide from heat exchanger tubes in the temperature range 900° to 1100°C in gas mixtures containing 2% Cl2 by volume with additions of O2 or H2 has been investigated by thermogravimetric analysis and subsequent examination of the corrosion products. The presence of a small amount of oxygen accelerated rapid active corrosion in chlorine‐containing gas mixtures, but the corrosion was suppressed by an active‐to‐passive transition when the concentration of oxygen in the gas mixture was too high. Low rates of attack were observed in the environments containing H2 even when the chlorine potential was high. The concentration of oxygen necessary to produce the active‐to‐passive transition was found to vary from one material to another and may be related to the amount of excess carbon in the sintered silicon carbide. Copyright © 1990, Wiley Blackwell. All rights reserved