The electrode's surface inhomogeneity was taken into account studying the mechanism of process. The effect of CN- adsorption and partial surface coverage was investigated by electrochemical fast Fourier transform (FFT) impedance spectroscopy (0.03-3900 Hz). The isopotential solutions (E-0 = -0.350 V) as well as solutions containing constant silver cyanide complex concentration (0.05 M) and different free cyanide ion concentrations (from 0.01 to 1.0 M) were studied. The exchange current density, re-calculated for only active area, gives electrochemical reaction order (R-CN = 1.8 for alpha = 0.5, and R-CN = 2 for alpha = 0.6) which is independent from CN- concentration and from the composition of complexes prevailing in the bulk of electrolyte. The value of RCN close to 2, obtained in a series of isopotential solutions confirms that in all cases the complex ions Ag(CN)(2)(-) take direct part in the charge transfer step. (C) 2003 Published by Elsevier Ltd.