Zinc + cobalt co-deposition was analyzed using potentiodynamic stripping of deposits. Results indicate the initial formation, on vitreous carbon, of a cobalt sub-monolayer. This formation explains the onset of the anomalous deposition process : zinc(II) adsorbs on the initial cobalt, and favours zinc deposition. The presence of zinc(II) exerts an inhibitory effect that hinders cobalt deposition. The formation of either pure zinc or zinc-rich deposits depends on the proportion of zinc(II) in the neighbourhood of the substrate. For the highest Zn(II)/Co(II) ratios, zinc(II) prevents the cobalt co-deposition and the deposit consists of pure zinc in a wide range of overpotentials and deposition times. A fast depletion of zinc(II) near the electrode is required for the co-deposition to begin. For zinc(TI)-rich baths small amounts of Sb(III) increase the cobalt content in the deposit.