Аннотация:The processes of mass transfer in the metal electrodeposition on a rotating disk electrode from thesolution containing three sorts of ions (electroactive metal cation and indifferent electrolyte containing inactivecation and anion) are studied theoretically. The Nernst–Planck equations in the approximation of thesolution electroneutrality reduced to a dimensionless form, which takes into account the elecrodiffusion andconvective transfer of all types of ions, are used as the mathematical model. The numerical solution of themathematical model is carried out by the finite volume method using a non-uniform grid. As a result of thenumerical solution, the distributions of potential and ion concentrations are obtained with taking intoaccount the interaction between the electric and hydrodynamic fields in the solutions with various concentrationsof supporting electrolyte at various diffusion coefficients of ions of all sorts. The dependences of thelimiting current of metal electrodeposition on the concentration of supporting electrolyte are obtained. Whencalculating the limiting current density in the absence of convection, the thickness of the Nernst diffusionlayer is calculated taking into account the effective diffusion coefficient of the solution with three sorts of ionsat various concentrations of supporting electrolyte. Using several examples with various ratios between thediffusion coefficients of the anion and inactive cation of the electrolyte, the error in the limiting current calculatedusing the Nernst diffusion layer approximation, as compared with the limiting current obtained takinginto account the convective transport of ions, is estimated.