Impedance of oxide film on zircaloy-2

Impedance measurement was performed on film grown on zircaloy-2 in steam at 400 deg C and 1500 psi for 3 and 20 days. Weight gains due to film on zircaloy-2 after 3 days and 20 days were 22.45 mg/dm2 and 41.83 mg/dm2 corresponding to film thicknesses of 1.53 μm and 2.85 μm respectively. Similar values were obtained from impedance data also. Impedance data were analyzed using equivalent circuits, modeling a two layer structure. Some electrolyte pick up is indicated by these experiments. Total impedance tends to decrease in 0.5 M H2SO4 over a long duration of exposure due to electrolyte pick up. In case of film grown in 0.5 M LiOH, increase in impedance was observed. Dispersion parameter for the inner layer capacity was close to unity while for outer layer it was less. (author)