Corrosion by Hot CO2 Gases

Heat-resisting alloys are designed to survive high-temperature oxidation by forming a slow-growing scale, usually Cr 2 O 3 , which acts as a barrier between the metal and its environment. However, alloys that succeed in this way when exposed to hot oxygen or air fail to do so in CO 2 gas. Instead, they exhibit rapid “breakaway” corrosion, developing oxides of alloy base metal iron and/or nickel. The growth of these non-protective scales is accompanied by internal carburization of the underlying alloy. Carbon passes through the oxide, dissolves in the alloy, and precipitates chromium as carbide. Removal of chromium from its matrix makes the alloy incapable of reforming chromia, and recovery from breakaway becomes impossible.