A sulphate bath for the preparation of Zn-Fe alloy coatings

Abstract

SUMMARYA new acidic sulphate bath was developed for the preparation of Zn-Fe alloy coatings. The percentage of iron in the deposits produced was measured by atomic absorption spectrophotometry and was found to be below 1.0 wt%. The bath composition was easy to control and when citric acid and sodium citrate were employed as buffer and complexing agents, respectively, stable pH values were observed. In addition, the operation cost was low and the cathode efficiency was high with respect to the alkaline baths. The Zn-Fe alloy coatings produced were fine and iridescent and no pinholes or pores could be observed over the surface. The percentage of iron in the alloy coatings increased with the increase of metal ratio Fe2/Zn2, and the applied current density. Bend tests indicated that the alloy coalings had good adhesion strength to the substrate.