Electrodeposition of Co-Ni and Co-Ni-Cu systems in sulphate-citrate medium

Electrodeposition of Co-Ni and Co-Ni-Cu alloys was performed in a sulphate-citrate medium. Experimental electrodeposition parameters (pH, cobalt(II), nickel(II) and citrate concentrations) were varied in order to analyse their influence on the deposition. Anomalous Co-Ni codeposition occured in the citrate medium. High [Ni(II)]/[Co(II)] ratios (above 5) were suitable for the preparation of homogeneous magnetic Co-rich Co-Ni deposits of hexagonal close-packed (hcp) structure or face centred cubic (fcc) structure as a function of the deposition potential. The presence of very low copper(II) concentrations (<10(-2) mol dm(-3)) in the nickel-cobalt bath makes it possible to incorporate copper in the deposits in amounts ranging from 5 to 60% Cu, although uniform deposits are obtained only for low copper percentages. These ternary deposits are solid solutions with fcc structure and magnetic behaviour both dependent on the deposition potential. (C) 2005 Elsevier Ltd. All rights reserved.