4. Primary Current Distribution and Electrode Geometry

The current density pattern on the surface of an electrode depends on the electrode shape and position [9, 11, 12, 14, 17]. It affects the corrosion behavior of the electrodes considerably. If electrode polarization is ignored, it was shown in [12] that on a disk electrode, with the surface in the same level as the surface of the surrounding insulator, the current density increases from the center of the disk while approaching the edge, with theoretically an infinite value at the edge. This assumption (no electrode polarization) can be made if the potential on the electrolyte side of the double layer is equal to that of the electrode. The current density under this condition is called primary current distribution. This state prevails at high frequency when the double layer capacitance behaves as a short circuit [14].