Characterization of the Corrosion Layers Electrochemically Formed on the Lead–Silver/H[sub 2]SO[sub 4]+Mn(II) Interface

Abstract

The corrosion layers electrochemically formed on the lead–silver/ interface were studied through open-circuit potential monitoring, cyclic voltammetry, and chronoamperometry and were characterized by cyclic voltammetry, X-ray diffraction, and scanning electron microscope coupled to an energy dispersive spectrometer to analyze microregions. Mn(II) oxidation reactions take place in the range of vs standard hydrogen electrode. When an oxidation potential pulse of 1.96 V is applied on a lead–silver electrode, different species are formed as the electrolysis time proceeds. This modification can be divided into four stages: at , is formed on the metallic lead; this compound favors the formation of . At , completely covers the surface, generating high current densities. At , the anodic layer loses its electroactive properties as it grows and and , which are less electroactive than , are formed. At , the formation of predominates, transforming the crystalline surface into an amorphous and nonelectroactive one. Furthermore, the anodic layer is broken, liberating and exposing metallic lead, which is oxidized to . The released forms on the electrode surface and in the bulk.