The electrochemical behaviour of pre-oxidized copper surfaces prepared by heating in air at 90 degrees C was studied to evaluate the impact of the air-formed oxide layer at the copper surface on the corrosion in an aggressive chloride medium. In a first part, the evolution of the chemical composition and the structure of the air-formed oxide layer with the heating time were investigated by cyclic voltammetry in an alkaline medium in which the different oxide species can be discriminated, X-ray photoelectrons spectroscopy experiments (XPS) and water contact angle measurements. It was demonstrated that short heating times produce Cu2O-rich films, while CuO-rich films were obtained after long heating-time periods. Furthermore, cyclic voltammetric data strongly support a stratification of the corrosion products in the mature oxide layer. In a second part, the protection efficiency of air-formed films, aged from 1 to 22 days, against the copper corrosion was study using a potentiodynamic technique and the electrochemical impedance spectroscopy (EIS) in an aerated 0.2 M NaCl aqueous electrolyte. Results demonstrate that the chemical composition of the air-formed oxide layer has an important impact in the overall corrosion process. Results are tentatively explained in terms of composition and structure of the oxide layer. (C) 2018 Elsevier Ltd. All rights reserved.