Electrodeposition of copper-nickel alloys from a citrate bath containing boric acid

Copper-nickel alloys have been electrodeposited on steel substrates from a bath containing copper sulphate, nickel sulphate, sodium sulphate sodium ci trate and boric acid. Galvanostatic cathodic polarization, cathodic current efficiency and composition of the alloys were studied as influenced by bat h composition, current density and temperature. The bath is characterized by high cathodic current efficiency. Current dens ity is found to strongly influence the composition of the deposits. At low current densities (lower than a certain transition current density), a copp er-rich alloy is deposited with copper (the more noble metal) being the pre ferentially deposited metal. Ar larger current densities, nickel becomes th e nobler metal and is deposited preferentially The magnitude of the transit ion current density depends upon the bath composition and temperature. The structure and surface morphology of the as-deposited alloys were examined b y XRD and SEM. The results reveal the presence of a single solid solution p hase with face centred cubic structure. The morphology of the deposits is m ainly controlled by the alloy composition.