In this part I of our work, the kinetics study of simultaneous cementation of nickel and cobalt from industrial zinc sulfate solutions using a rotating zinc electrode disc was investigated. Experiments were carried out in the presence of copper to increase the low cementation rate of these elements (Ni and Co). The effect of temperature, metallic ions concentrations and electrode rotation speed was also investigated. The reaction of nickel cementation was found to be under diffusional control while that of cobalt was found under chemical control. The reaction rate was found to be strongly affected by the increase in the electrode surface area. Mass transfer study of the process was correlated by the equation: Sh = 1.43Sc(0.33) Re-0.49. The results obtained will be used to establish optimal conditions for the zinc production plant of ALZINC, Tlemcen, Algeria. (c) 2006 Elsevier B.V. All rights reserved.