Bipolar electrode behaviour of the aluminium surface in a lateral electricfield

This paper reports on the electrochemical processes at the surface of condu cting materials such as aluminium in a thin-layer cell usually employed for electrokinetic measurements. The cell contains one or more planar Al wafer s in contact with an electrolyte solution, which is subjected to an externa l electric field parallel to the surfaces of the wafers. Beyond a certain t hreshold value of the magnitude of the field, the current through the cell increases more than proportionally with the field strength. This is due to faradaic processes occurring at the two ends of the conducting substrates, i.e. reduction at the positive side of the electric field in the solution a nd oxidation at the negative side. In the case of Al wafers, anodic dissolu tion of the metal takes place and the progression of the 'corroding' edge c an be followed visually. The overall electrolytic process, corresponding wi th the distributed current along the surface of the wafer, could be explain ed and modeled on the basis of the conventionally measured Butler-Volmer ch aracteristics of the monopolar Al electrode. . (C) 2001 Elsevier Science B. V. All rights reserved.