EFFECT OF NICKEL ON THE ELECTRODEPOSITION OF COPPER

The mechanism of copper electrocrystallization from various solutions has been investigated to determine the influence of foreign cations and, particularly, of nickel. The study was performed by cyclic voltammetry and scanning electron microscopy. In sulphate solutions the Na+ and NH4+ cations affect the copper deposition by changing the nucleation overpotential and the presence of nickel cations makes the copper deposition easier by deceasing the nucleation overpotentials of both copper and nickel. In chloride solutions, the strong adsorption of the chloride species prevents all other influences by blocking the active sites of nucleation and growth and, therefore, Na+ or NH4+ addition does not modify the copper deposition. Consequently, the nickel does not modify the nucleation overpotential of copper. Whatever the solution, sulphate or chloride, the anodic behaviour of the copper-nickel codeposits are similar to the anodic behaviour of bulk Cu-Ni alloys.