X-ray diffraction and infrared spectrometry of thermal oxidation of ferritic stainless steel conversion coatings for photothermal conversion

The iron oxide which predominates inferritic stainless steel conversion coatings for photothermal conversion is a chromium substituted magnetite (Fe2+Fe3+2−x Cr3+ x )O2−4: the chromium content of this magnetite could be at least that of the stainless steel substrate (x≥0·5). This substituted magnetite coexists with a partially oxidised magnetite. The thermal treatment of these coatings induces theformation of the corundum type phase α Fe2O3 by oxidation of the substituted magnetitefrom 175°C. At higher temperatures, FeCr2O4 and α Fe6−yCryO9 appear.MST/1216