Effect of nickel on the electrodeposition of copper

The mechanism of Cu electrocrystallization from various solutions has been investigated to determine the influence of foreign cations and, particularly, of Ni. The study was performed by cyclic voltammetry and scanning electron microscopy. In sulphate solutions the Na exp + and NH exp 4+ cations affect the Cu deposition by changing the nucleation overpotential and the presence of Ni cations makes the copper deposition easier by decreasing the nucleation overpotentials of both Cu and Ni. 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 exp + or NH exp 4+ addition does not modify the Cu deposition. Consequently, the Ni does not modify the nucleation overpotential of Cu. Whatever the solution, sulphate or chloride, the anodic behavior of the Cu--Ni codeposits are similar to the anodic behavior of bulk Cu--Ni alloys.