This work compares the oxidation behaviour of three iron-based substrates (C40E, Invar and 304L) in CO2 industrial gas, in order to determine the conditions for producing wüstite (Fe1-xO), on the basis of kinetic and morphologic studies. For the three alloys at the beginning of the reaction, wüstite formed under 105 Pa of CO2 following a rate law RT 220000 10.2 P e dt d( m/S) CO2 . For 304L, formation of a spinel phase chromite briefly preceded it during a first step. Magnetite appeared for long times of experiment, in the case of Invar and 304L. This can be explained by the stopping of iron outer diffusion. These results are discussed according to the literature and thermodynamic data. They open new fields for coating these alloys by plasma spray processes.