Electroplating of a Co-Cu alloy from a citrate bath containing boric acid

The effects of bath composition, current density and temperature on cathodi c polarization, cathodic current efficiency of codeposition, composition an d structure of Co-Cu alloys electroplated on a steel substrate from citrate baths have been studied. Addition of boric acid to citrate electrolyte inc reases the percentage of Co in the deposits and improves the quality of the se deposits. The cathodic current efficiency of the baths is relatively hig h and increases with increases in the metal content in the bath and the cur rent density but decreases with temperature. The composition of the deposit is controlled by the applied current density. At low current densities, Cu -rich alloys were obtained. At higher current densities, the composition of the alloys was controlled by the limiting current density of Cu codepositi on. The Co content of the deposits increases with increases in the metal co ntent in the bath and the temperature. The structure of the deposited alloy s was characterized by anodic stripping and X-ray diffraction techniques. T he deposited alloys consisted of a single solid solution phase with a face- centred cubic structure. (C) 2000 Society of Chemical Industry.