The electrochemical behaviour of the highly alloyed austenitic stainless steel UNS N08031 (Alloy 31) in a contaminated phosphoric acid solution is studied using potentiodynamic curves, EIS and Mott-Shottky. The relative stability of the films formed on Alloy 31 has been studied after a pre-passivated treatment at 0.3, 0.5, 0.8 and 1 V-Ag/AgCl. potentials within the passive domain. The protection of Alloy 31 was provided by the inner oxide film, while the outer film was more defective. The electronic-semiconducting properties of the passive films have been correlated to corrosion resistance. Passivated Alloy 31 at 0.8 V-Ag/AgCl showed lower concentration of charge carriers, which beneficially affects the protecting and electronic properties of the passive oxide film. (C) 2012 Elsevier Ltd. All rights reserved.