The surface oxidation of duplex stainless steel (DSS 2205) was studied by X-ray photoelectron spectroscopy (XPS). The experiments were performed on the alloy after controlled oxidation in a chloride-enriched solution at controlled potentials. The evolution of the passive film formed on the DSS in a chloride solution was studied using cyclic voltammetry with XPS surface characterization at selected potentials. The evolution of the oxide films and its specific compositions formed on the DSS was studied as a function of depth. Fe/Cr oxidized layers and oxide thicknesses were observed and correlated with the various potentiostatic potentials. The importance of Mo and Cr inside the oxide films in this article is studied and described, whereas their role in the protective layer, as oxides, is significant.