Electrodeposition of iron-group metals and binary alloys from sulfate baths I. Experimental study

Thin films of the iron-group elemental metals (Ni, Co, and Fe, group VIIIB) and binary alloys (NiCo, CoFe, and NiFe) were galvanostatically electroplated onto a platinum rotating disk electrode from simple sulfate baths. In all cases, the increasing electrode rotational rate was found to decrease the partial current densities at a given cathodic potential. Experimental results indicate that for electrodeposition: two distinct rate-determining steps exist, partial current densities for metal deposition are not linearly related to bulk metallic concentration, and the partial current densities for hydrogen evolution are found to reach a plateau for each metal sulfate bath and rotational rate studied. For the conditions studied, comparison of the partial current densities for elemental and alloy deposition shows that the more noble metal deposition is unchanged or inhibited in alloy codeposition, while that for the less noble metal is promoted.