The nucleation and growth of Ag(I) oxide layers on polycrystalline Ag electrodes is studied by potentiodynamic and potentiostatic current transients in 0.1 M NaOH. A model involving the diffusion controlled growth of a basal layer followed by the nucleation and growth of a secondary layer is proposed. Various nucleation parameters are estimated by comparing experimental data with simulated transients, and the results are discussed in terms of the atomistic theory of electrochemical phase formation. The influence of the nucleation parameters on the shape of the current transients is analysed and some controversial results in the literature are explained.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasFacultad de Ciencias Exactas