Potentiodynamic behaviour of aluminium in propanedioic acid solutions

Abstract

The electrochemical behaviour of aluminium in propanedioic acid solutions has been studied potentiodynamically, the sweep rates ranging from 1 to 100 mVs⁻¹ and the concentrations of the diacid being 0.05, 0.10, 0.50 and 1.00 m. The experimental work has been carried out with and without stirring of the electrolyte. The potentiodynamic curves are simple but reflect a complex behaviour. The potential of zero current in the anodic sweep is made considerably more anodic when the concentration of propanedioic acid increases, when the sweep rate decreases and when stirring is introduced. For a certain sweep rate the cathodic charge increases with both stirring and concentration of propanedioic acid. However, the anodic charge, although increasing with concentration, does not depend on stirring within experimental error (potential ranges between −2.00 and 0.400 and −2.00 and 2.90 V vs SCE). The experimental curves are explained by the increase of the quantity of reducible species near the electrode with diacid concentration, by the fact that the cathodic process is pore diffusion-controlled (H₂ evolution) and that near the potential of zero current the cathodic and anodic processes coexist (oxide formation and possible direct migration of the cation towards the solution).