The adsorption of borate ions at the nickel and/or nickel oxide-electrolyte electrochemical interface was studied at various concentrations and pH values in lithium and borate solutions. First, the passivation range of nickel was estimated using cyclic voltammetry. The nickel passive layer formation kinetics ( transfer resistance, capacitance of passive film formed, adsorption capacitance), as well as the semiconducting properties of this oxide layer, were studied using electrochemical impedance spectroscopy (E.I.S.). These electrochemical techniques were used in conjunction with adsorption measurements performed with an electrochemical quartz crystal microbalance ( E. Q. C. M.) and with surface analyses (Auger spectroscopy). The nickel oxide showed type p semiconducting properties and was depleted at, corrosion potential. Moreover, very little borate adsorption was observed during the different tests. This may have been the result of the negative surface charge, in the pH and potential conditions applied. (C) 2003 Kluwer Academic Publishers.