In order to protect the state-of-the-art nickel cathode used in the molten carbonate fuel cell, electrochemical potentiostatic deposition, a cheap and low-temperature technique, has been used to produce a cobalt oxide coating. This process was optimised on nickel substrates, analysing thoroughly the effect of the imposed potential, electrolyte composition, pH, electrolysis duration and the pre-oxidation of the substrate. Thin and homogeneous cobalt oxide layers were elaborated, in particular, in nitrate media at pH 7.4 on a nickel substrate previously oxidised. The structure and morphology of the deposits were characterised either directly or after an annealing treatment, by X-ray photoelectron spectroscopy, X-ray diffraction and scanning electron microscopy. A cubic Co3O4 structure was identified, which is in agreement with the results obtained by cyclic voltammetry. (C) 2003 Elsevier Science B.V. All rights reserved.