Interfacial Phenomena at Solid Aluminum Electrodes in Solutions of AlBr3 /KBr in Aromatic Hydrocarbons

Solutions of AlBr3 and KBr in toluene, mesitylene, or their mixture have been prepared under high purity conditions on a vacuum line. Anodic dissolution and cathodic deposition at a pure aluminum electrode were studied. Special attention was focused on the mechanism of rupture of the oxide film initially present on the surface and the formation of pits under the surface. The apparent exchange current density was found to depend on the anodic current density employed to activate the surface. The current density was found to be a linear function of potential over ca. 0.2V on both sides of the reversible potential. This was interpreted as being due to the solution resistance inside small flaws (pinholes) in the oxide layer on the surface.