Gold oxidation in a sulfuric medium was investiged by means of cyclic voltammetry and electrochemical impedance techniques. The experimental results were compared with a three-step reaction mechanism model which also explains the experimental voltammograms. The theoretical evolution of the surface coverages of the adsorbed reaction intermediates and the partial currents related to each elementary steps were calculated vs. the potential. An equivalent electrical circuit was proposed and the values of some of the components estimated.