The anodic formation of Cu2O on electropolished polycrystalline copper has been examined galvano-statically in a borate buffer solution over a range of current densities and temperatures. A model for film formation based on rapid formation of oxide nuclei followed by their lateral growth has been developed and shown to be in quantitative agreement with the data. According to this model, an oxygen-containing adsorbed intermediate, formed in an electrochemical step, reacts with metal at the peripheries of oxide patches to form more oxide. Both one- and two-dimensional lateral growth mechanisms were considered, the former being found to represent the data appreciably better. Assuming the initial electrochemical step to be [Formula: see text], where (OH)s represents the adsorbed intermediate, the first-order rate constant, kf calculated at the equilibrium electrode potential, is given by kf = 1013.3exp(−19 400/RT)s−1.