CHARACTERIZATION OF PASSIVE LAYERS FORMED ON LEAD BY ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY

The corrosion process and characteristics of the surface layer formed on lead in concentrated sulphuric acid solutions were studied using electrochemical impedance spectroscopy (EIS) and rotating-disc electrodes. Data obtained under a wide variety of experimental conditions show that the surface films generated in the passive potential range consist of various Pb(II)-containing species. The inner barrier PbO layer, which builds up progressively beneath the initially grown PbSO4 porous layer, behaves as a p-type semiconductor. The influence of its formation potential on the semiconducting properties and diffusion processes is discussed from impedance spectra by application of transfer-function analysis using non-linear fitting routines.