The aluminium electrode potential

A square wave current technique has been used to obtain the cathodic overvoltage parameters for hydrogen evolution on aluminium but was found inadequate by itself for determining the anodic parameters for aluminium dissolution, mainly because of the complicating effects of solution IR drop. A method was developed, however, for the determination of αa and the ratio C/i oa from the analysis of the initial potential fall 20 μsecs during and just after cutting. By combining these results with the square wave results, the IR drop and i oa were found and hence C could be obtained from C/i oa. It shown that the potential time behaviour in the first few milliseconds on freshly exposing an aluminium, surface to aqueous salt solutions cannot be explained simply in terms of the electrode kinetic parameters applicable to the existing polyelectrode. The observations have been accounted for using polyelectrode parameters if the ratio of cathodic to anodic area changes rapidly (T.C. 0.2 ms) with time after an effective delay of approximately 20 μsecs