Anodic linear sweep voltammetric analysis of Ni-Co alloys electrodeposited from dilute sulfate baths

Anodic linear sweep voltammetry was used to characterise electrodeposits of Ni, Co and five Ni-Co alloys (5:1, 2:1, 1:1, 1:2 and 1:5 ratios) obtained in a potentiodynamic mode on a vitreous carbon electrode from dilute sulfate baths. The voltammetric results showed a complex behaviour, with the deposits strongly dependent on the metal ion concentrations and less dependent on the final deposition potential. Probably due to simultaneous hydrogen evolution, the efficiency of the electrodeposition (in sulfate baths) and electrodissolution (in ammoniacal bath) processes of pure Co and Ni-Co alloys decreased with increasing final potential in all solutions, while that of pure Ni was enhanced with a shift to more negative potentials. Morphological information was acquired through investigations by techniques such as SEM, EDX and dot mapping. The voltammetric results revealed solid solution characteristics, with profiles varying from pure Ni to pure Co. The results of semi-quantitative EDX chemical analyses suggest a regular deposition mechanism instead of an anomalous one as is often observed in such binary systems.