A hybrid method through Faradaic rectification and a.c. impedance measurements for the corrosion rate determination of metal/oxide/electrolyte systems. II. Experimental results for anodized aluminium

An experimental verification of a method for the determination of the corrosion rate of metal/oxide/ electrolyte systems, using both faradaic rectification and a.c. impedance measurements, is reported using zone refined aluminium electrodes in 1 mol dm^–3 aqueous sodium sulphate at pH 1.9. The impedance and the rectification parameters due to the anodic oxide on the electrode have also been computed and used to determine instantaneous corrosion rate of the same system at different values of the pH. The direction and magnitude of rectification by this system are found to be sensitive to pH as well as dissolved oxygen in the electrolyte. They are explained by a decrease in equilibrium exchange current for the hydrogen evolution reaction with increase in pH and an inhibitive effect of oxygen on the former reaction.