Considerations in Mechanisms of Copper and Nickel Electrodepositions

Observations and discussions were made for the mechanisms of electrodepositions of copper from sulfate and cyanide baths and of nickel from sulfamate and sulfate baths. The behavior of initial crystal nucleation and crystal growth was observed under an electron microscope. Main considerations obtained were as follows: (1) The electrodeposits of Cu and Ni were nearly identical in crystal forms, because the both metal had the same crystal lattices (face centered cubic lattices). (2) Different types of electrodeposited crystals were observed between simple salt and complex salt baths. (3) Initial crystal nuclei had semi-spherical form with diameter of less than 3000Å. The machanism of nucleation was supposed to consist of the followig three stages; that is, the presence of a huge ionic mass in the electrolytic bath, its continuons discharge, and instantaneous deposition of the corresponding metal. (4) The nucleation seemed to be concentrated around the scratches on the substrate caused by grinding and in the neighborhood of grain boundaries of crystals.