Review of the development and breakdown of protective oxide scales on alloys exposed to coal-derived atmospheres

Abstract

Metal components in coal utilization and conversion systems are subject to severe corrosion by sulfur and other impurities in coal-derived environments. Most of the alloys and metallic coatings designed to withstand high-temperature aggressive environments rely on the formation of protective Cr 2O3 and Al 2O3 scales. However, in mixed-gas environments containing sulfur, either the protective oxide scales do not form or they rapidly break down. In order to understand corrosion behavior in mixed-gas environments, previous work on corrosion of high-temperature materials in coal-related applications is summarized. Current ideas for the development of protective oxide scales on alloys in mixed-gas environments by preoxidation and by the addition of reactive elements to the alloys are reviewed. Finally, future studies are recommended as being important to the development of alloys with better corrosion resistance in mixed-gas environments.