An approximate analytical solution of problem of ion transfer near a vertical plane electrode surface is obtained for the metal electrodeposition proceeding at the limiting current from electrolyte containing ions of three types under the conditions of natural convection. In contrast to previous studies, no transport numbers are used here, and the migration transfer of electroactive electrolyte component is taken into account. The equations obtained take into consideration the effect of supporting electrolyte concentration and its migration on the limiting current. The limiting current densities (mass-transfer coefficients), which are calculated by equations proposed here and by the finite-difference method, are compared. (C) 2003 Elsevier Ltd. All rights reserved.