Self-assembled monolayers (SAMs) formed by the adsorption of alkanethiols onto copper is a simple method for producing coatings that can protect the metal against oxidation and corrosion. However, a contradiction regarding the influence of oxygen on the SAMs formation and barrier properties is still present. In this work the SAMs of dodecanethiol (DT) were formed on the copper substrates from ethanolic solutions of DT with and without the presence of dissolved oxygen. The protecting properties of monolayers were studied in a sodium acetate solution with a pH of 6 using cyclic voltammetry and electrochemical impedance spectroscopy. The effect of exposing samples, prepared in the deoxygenated solutions, to air was also studied to examine the decrease in the protecting properties of the SAMs against copper corrosion. The protection efficiency of the DT SAMs was compared with those of benzotriazole, which is known as the best inhibitor for copper corrosion. (c) 2006 The Electrochemical Society. All rights reserved.