KINETICS OF THE ALPHA-FE2O3 FORMATION ON FE3O4 BETWEEN 400 AND 570-DEGREES-C STUDIED BY MEANS OF X-RAY-DIFFRACTION WITH GRAZING-INCIDENCE

The formation of alpha-Fe2O3 on Fe3O4 during the oxidation of iron below 570-degrees-C occurs very slowly and the scales are so thin that they cannot be detected by microscopy. X-ray diffraction with grazing incidence, equipped with a high temperature device, allows an 'in situ' study of the alpha-Fe2O3 formation even the initial reactions. The formation of alpha-Fe2O3 Was studied in isothermal experiments at 400, 450, 500 and 550-degrees-C. Alpha-Fe2O3 could already be detected at the beginning of the experiments. The difference method, a numerical treatment for kinetic evaluation, yields curves showing the growth of the alpha-Fe2O3 layer. Fitting the parabolic time law to these curves yields the rate constants.