Cobalt Electrodeposition Process from Electrolytic Baths based on CoSO4 and (NH4)2SO4. Influence of [Co(II)]

In this work we carried out an electrochemical study of the cobalt electrodeposition from ammonium sulfate solutions (x CoSO4 + 1M (NH4)2SO4, where x=0.005, 0.01, 0.05 and 0.1M) onto glassy carbon electrode. From the potentiostatic study, it was obtained that the nucleation rate increases with the increment of cobalt in the plating bath. From our thermodynamic study we found that the [Co(H2O)6]2+ chemical specie was the predominant complex. The conditional equilibrium potential (Eq) depends on the cobalt concentration in the solution, thus an increase in [Co(II)] decreases the Eq. A clear linear tendency in the plot lnA vs E was observed for systems II and III. However, non linear plots were gotten for systems I and IV, indicating the existence of additional processes that affects the nucleation and growth mechanisms.