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

The iron content, phase constitution, and microstructure of electrodep osited iron-zinc alloy coatings deposited from chloride baths were inv estigated. It was found that the iron content of the coatings varied w ith the current density used during processing and that coatings conta ining 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 eq uilibrium 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/polygonizati on process.