Aspects of High Temperature Corrosion of Metals by Gases

Abstract

The paper surveys high temperature corrosion phenomena involving diffusion-controlled growth of continuous scales. Lattice diffusion is generally rate-determining only for scales with relatively high concentrations of point defects and at high temperatures, e.g. oxidation of Co to CoO above about 1000 °C. At more reduced temperatures and for scales with relatively low point defect concentrations scale growth predominantly takes place by grain boundary diffusion, e.g. growth of NiO, Cr2O3, and A12O3. The common use metals may corrode rapidly in many sulfur-containing atmospheres due to the formation of sulfide phases which are highly nonstoichiometric and exhibit high rates of diffusion. This is illustrated for corrosion of metal and dilute nickel alloys in O2+SO2/SO3 atmospheres. It is emphasized that the distribution of the sulfide phases in the scales is important for the reaction mechanisms.