The Randles-Sevcik relationship was used to evaluate at. H-2 diffusivity in LaNi45Co0.5 composite electrode at low polarization rates (0.01-0.1 mV/s). The electrodes were cathodically hydrogenated before voltammetric measurements to provide them H-2 concn. 0.06 mol/cm(3). The effective diffusion coeffs. were affected by errors from the actual surface area of the active material (S), therefore more reliable for evaluation is the ratio of (SDH)-D-2.