A boric acid bath for ZnNi alloy electrodeposition was developed with mannitol as additive. The deposition process was investigated by cyclic voltammetry. It was found that the current density decreased, due to adsorption of a boric-mannitol complex and/or changes in the morphology, but the initial deposition potential was not affected. At deposition potentials more negative than -1.20 V, the current efficiency obtained was high (80-85%) in all baths studied. The addition of mannitol to the bath led to the formation of the best ZnNi deposits, composed of coalesced globular grains smaller than similar to 1 mu m in diameter. Also, all of the ZnNi deposits studied consisted of gamma, gamma(1), and Pt3Zn phases. The Ni content in the ZnNi deposits produced in the presence of mannitol increased from 6 to 10 wt% only in the range -1.26 to -1.40 V. It is suggested that the ZnNi deposits produced in these baths probably offer sacrificial protection to the substrate.