In situ radiochemical and electrochemical studies of cobalt accumulation on polycrystalline gold electrode in NaClO4 and berate buffer solutions were carried out. From the results it can be stated that the extent and kinetics of sorption are decisively dependent upon the pH of the solution. At open-circuit potential the accumulation process is associated with the formation of hydrolysis products of cobalt. It is shown that the presence of borate species suppresses the cobalt uptake on the gold electrode. The mechanisms of cobalt accumulation during cathodic and anodic polarization in NaClO4 and berate buffer solutions are different. It has been found that (i) oxide layers containing Go-species are formed on gold at potentials more positive than 1.050 V; (ii) the composition of oxide films is influenced by the nature of the supporting electrolyte used; (iii) peculiarities appear in the formation and decomposition of surface oxides that are most likely due to not only Co(OH)(2) but Co2+ species.