Morphology Evolution of Zinc‐Nickel Binary Alloys Electrodeposited with Cadmium Additive

Abstract

Zinc‐nickel electrodeposits have been widely adopted for surface treatment of automobile body steel sheet. Cadmium additive enhances nucleation of hexagonal columnar crystals of the zinc‐nickel electrodeposit. These hexagonal columnar crystals are made up of lateral growth of hexagonal plates along the (00·1)η. With 30 ppm of cadmium, cadmium absorbs at active sites on the (00·1)η. and interferes with surface diffusion of metal adatoms. This enhances nucleation and forms many hexagonal plates on the (00·1)η. With 100 ppm of cadmium, not only do many hexagonal plates on the (00·1)η but also fine hexagonal columnar crystals form on the {10·0}η. With further increase of cadmium to 200 ppm, the entire deposit becomes fine hexagonal crystals.