In the present work, electrode process in the system CU/CuSO4 + H2SO4 is considered as a sum of two single-electron electrochemical reactions that occur simultaneously on copper electrode. Numerical modelling of this process was performed taking into account diffusion, electromigration. and chemical interactions between the components of the solution. The results of calculations do not contradict the experimental facts known for this system. The behaviour in the region close to the open circuit potential can be explained by the differences in the partial currents of the reactions proceeding on the electrode. The behaviour of the surface concentrations of the components of solution in the region of the anodic overpotential points to a substantial role of electromigration processes that can be played by them in copper passivation in sulphate solutions. 2004 Elsevier Ltd. All rights reserved.