Alloy degradation under oxidizing-sulfidizing conditions at elevated temperatures

exposure of high-temperature alloys to a low-po2 oxidizing-sulfidizing environment above about 550 °c is often characterized by an initial period of protective oxidation followed by more rapid corrosion. this paper will provide a brief overview of alloy corrosion in oxidizing-sulfidizing atmospheres, with specific consideration given to the thermodynamic and kinetic aspects of the process, resulting modes of degradation, and alloy selection. the concept of a "critical microstructure" in the subsurface of the alloy as a prerequisite to initiating protective scale breakdown will also be discussed. the paper will conclude with a specific example of alloy development for the filtration of hot oxidizing-sulfidizing gases.