Interpretation of the Impedance Properties of the Anode-Surface Film in the Electropolishing of Copper in Phosphoric Acid

The frequency dispersion of the impedance measured by Ohashi et al., between a vertical copper anode and a reference electrode during electropolishing in concentrated phosphoric acid, is analyzed in terms of linear combinations of resistors and capacitors. The frequency dependence of the anode under electropolishing conditions may be satisfactorily represented by an analogue circuit consisting of a resistor and a capacitor connected in parallel. The resistivity is in the range of while the capacitance is . The contribution of the solution‐side resistance to the total impedance is small. Assuming that the solid film layers on the anode surface are composed of oxides of copper, depending on actual composition, the measured impedances are consistent with a thickness range of 13–124Aå.