Morphology evolution of zinc iron binary alloys electrodeposited with copper additive

Zinc-iron electrodeposits have widely been adopted for surface treatment of automobile body steel sheet. Copper additive enhances dendrite formation of hexagonal columnar crystals of the zinc-iron electrodeposit. With 100 ppm of copper, these crystals show fine steps on {10.0}eta surfaces. With 150 ppm, the copper enhances nucleation on one of an apex on (00.1)eta of these crystals. With 300 ppm, the nucleation increases and fine platelet crystals precipitate preferentially at this apex. With further increase of copper to 1000 ppm, the deposit becomes dendrite crystals and this apex becomes the growing tip of the dendrite.