Composite coatings Ni/Al2O3 were electrochemically deposited from a Watts bath. Al2O3 powder with particle diameter below 1 mu m was codeposited with the metal. The obtained Ni/Al2O3 coatings contained 5-6% by weight of corundum. The structure of the coatings was examined by scanning electron microscopy (SEM). It has been found that the codeposition of Al2O3 particles with nickel disturbs the nickel coating's regular surface structure, increasing its mictocrystallinity and surface roughness. DC and AC electrochemical tests were carried out on such coatings in a 0.5 M solution of Na2SO4 in order to evaluate their corrosion resistance. The potentiodynamic tests showed that the corrosion resistance of composite coating Ni/Al2O3 is better than that of the standard nickel coating. After 14 days of exposure the nickel coating corrodes three times faster than the Ni/Al2O3 coating. The electrochemical behaviour of the coatings in the corrosive solution was investigated by electrochemical impedance spectroscopy (EIS). An equivalent circuit diagram consisting of two RC electric circuits: one for electrode, nickel corrosion processes and the other for processes causing coating surface blockage, were adopted for the analysis of the impedance spectra. The changes in the charge transfer resistance determined from the impedance measurements are comparable with the changes in corrosion resistance determined from potentiodynamic measurements. (c) 2005 Elsevier Ltd. All rights reserved.