The effect of CN- adsorption and partial surface coverage of silver electrodes in KCN containing electrolytes was investigated by electrochemical impedance spectroscopy (EIS). A fast Fourier transform (FFT) impedance spectrometer was used. Series of time-resolved EIS measurements were performed after the electrode had been immersed in the electrolyte. The impedance spectra obtained were used to determine the time evolution of the surface blocking taking place on the silver electrode after its immersion into electrolytes of different CN- ion concentrations. It is shown that the surface coverage depends on the CN- concentration, whereby the extent of silver surface blocking settles down in the first 20-60 s after electrode immersion.