Kinetics of Manganeseo-Wustite Scale Formation on Iron-Manganese Alloys

Abstract

The oxidation kinetics of Fe‐Mn alloys containing up to 59 w/o (weight per cent) Mn exposed to carbon dioxide‐carbon monoxide atmospheres at 1000°C have been determined by a thermogravimetric technique. The experimental conditions were chosen in order that the reaction would lead to formation of a single‐phase manganeseo‐wustite scale. The rate of parabolic oxidation decreased and the manganese content in wustite increased with increasing manganese content in the alloy. A diffusion model, which is based on equations derived by Wagner for metal diffusion through the scale under chemical activity gradients, leads to a description of the scaling kinetics, and to evaluations for the self‐diffusion coefficients of iron and manganese and the nonstoichiometry as a function of the manganese content in wustite.