Effect of Cd2+ on the electrodeposition of nickel from sulfate solutions. Part II: Polarisation behaviour

The effect of Cd2+ on the electrodeposition of nickel from a sulphate bath in the absence and presence of boric acid has been investigated. The presence of Cd2+ ion suppresses the nickel electrodeposition and shifts the deposition potential to more negative values. The cathodic polarisation is found to depend on the composition of the electrolytic bath. For the various baths investigated, the cathodic polarization order is found to decrease in the order NiSO4 + H3BO3 > NiSO4 + H3BO3 + Na2SO4 > NiSO4 + Na2SO4 > NiSO4. For the Ni2+ electroreduction reaction on stainless steel and nickel substrates the exchange current density decreases with increase in Cd2+ concentration in the electrolytic bath. However the Tafel slope and transfer coefficient are unaffected.