Perturbation of the Flow of Current to a Disk Electrode by an Insulating Sphere

A quantitative basis for the interpretation of the electrochemical noise generated either by particles approaching an electrode during composite plating or by bubble formation at a gas evolving electrode is presented. Heretofore, the increase of the electrolyte resistance of the flow of current to a disk electrode caused by an insulating sphere was determined experimentally and theoretically. The experimental study was carried out by displacing a glass or corundum ball glued to a glass fiber by means of a translation stage in front of a small disk electrode embedded in an insulator. The high frequency limit of the ac Impedance was used to avoid electrode polarization effects. In parallel, the incremental resistance due to the sphere was calculated theoretically by using a recently developed model based on a boundary collocation method which was specially developed for this purpose. Theoretical and experimental values were found to be in excellent agreement, the deviations being due to the limited experimental accuracy of the resistance measurements.