Electrodeposition of Co-Ni alloys from citrate bath onto steel substrate

Cobalt-nickel alloy have been electrode-posited from a bath containing meta l salts such as cobalt, nickel sulphate and sodium citrate as a complexing agent. Boric acid is used as a buffer solution. An interesting feature is t hat anomalous deposition type is obtained, where nickel deposition is promo ted at high current densities. It is advisable to say that there is a trans ition current density (i(trans.)) which is sensitive to bath composition an d temperature. X-ray and SEM examined the structure and surface morphology the deposited alloys. The results revealed that the alloy consisted of a si ngle solid solution phase with facecentered cubic structure (FCC). Increasi ng of either current density or temperature gives more compact and massive structure.