engleski

Electrochemical and surface processes on oxide covered aluminium

The electrochemical and surface processes on aluminium electrode covered by a thin surface oxide film in citrate buffer solutions (pH=2-8) was studied, by the means of potentiodynamic, cyclic voltammetry, transient and electrochemical impedance spectroscopy techniques. The results show that in citrate solutions aluminium exhibits typical passive behaviour due to formation of a thin barrier-type of passive film. The dissolution (corrosion) of aluminium in these solutions is intimately connected with the properties of its surface oxide film and the processes which occur at the oxide/citrate solution interface. On the aluminium oxide surface proceeded different electrochemical, chemical and surface processes: hydration of aluminium-oxygen bonds and formation of surface hydroxyl groups, dissociation of hydroxyl groups what leads to the possibility of different surface coordination reactions (such as adsorption and surface complexation), dissolution of aluminium oxide film and formation Al-complexes in the solution. The results of this investigation suggests that dissolution (corrosion) of aluminium in citrate solution is a very complex process in which surface processes play a significant role. The mechanism of dissolution is determined mainly by the pH of solutions. In citrate solution of pH 3-6, dissolution of aluminium is essentially controlled by the rate of detachment of surface Al-complexes, while at pH=2 and pH=7-8 electrochemical mechanism of dissolution prevailed. Dissolution at these pH values was relatively high and is controlled by the mass transport.

aluminium; oxide film; electrochemical processes; surface processes

nije evidentirano