The effect of the physico-chemical characteristics of Co3O4 powders on their reactivity in solution and their incorporation in a nickel matrix has been investigated in a Watts nickel plating bath. The results showed that the surface area of the powder present in suspension not only catalyses the adsorption or desorption phenomena occurring at the particle/solution interface but also has a significant effect on the incorporation of the particles into the nickel matrix. It has been found that the use of Co3O4 With high specific surface area (40 m(2) g(-1)) significantly limits the growth rate of the electrodeposited composite coatings. Furthermore, it has been shown that the codeposition of these more reactive particles leads to significant changes in the microstructure and texture of the nickel matrix. Finally, it has been found that, according to their specific surface areas, the amount of H+, Ni2+ and Ni[B(OH)(4)](+) ions adsorbed on the Co3O4 oxide surfaces and the quantities of particles codeposited can vary considerably.