STRUCTURE OF AS-DEPOSITED IRON-ZINC COATINGS FROM CHLORIDE BATH

The iron content, phase constitution, and microstructure of electrodeposited iron-zinc alloy coatings deposited from chloride baths were investigated. It was found that the iron content of the coatings varied with the current density used during processing and that coatings containing 6 to 13 wt pct Fe consisted of nonequilibrium phases, eta and G. Eta phase, hexagonal close-packed (hcp) zinc supersaturated with iron to about 8 wt pct Fe, contained nanometer-size crystals divided by 30-nm-wide growth steps. Within the growth steps, an amorphous phase was present. The G phase, a body-centered cubic (bcc) phase similar to equilibrium gamma phase, existed as equiaxed 30- to 80-nm-wide grains in 10 and 13 wt pct Fe coatings. It is suggested that the microstructure of higher iron content-coatings resulted from a recovery/polygonization process.