Rezumat
The influence of ion mass-transfer effects on the deposition rate, current efficiency, composition and morphology of coatings was studied using a rotating cylindrical electrode in citrate electrolyte containing CoSO4 (0,2 mol/l) and Na2WO4 (0,2 mol/l), pH = 6,8, at electrodeposition temperature of 60ºC. It was found that lowering of electrodeposition potential, decreasing of tungsten concentration in coatings; increasing current efficiency with rising of Re number, when Re ≥ 200 are occurred only in galvanostatic conditions, not in potentiostatic. It was shown that the observed effects are caused by electrodeposition through the nonstoichiometric surface covering layer with the electronic conductivity, the components of which are in electrochemical equilibrium with the components of the solution on the film-solution boundary.