Manganese dioxide as a potential cathodic reactant in corrosion of stainless steels

Biofilms of Leptothrix discophora SP-6, grown on 316L stainless steel (SS), ennobled the open circuit potential to 410 mV(SCE). X-ray Photoelectron Spectroscopy (XPS) identified MnO2 within these biofilms. Field exposed SS showed similar ennoblement after 30 days. XPS analysis of these samples revealed a mixture of different manganese minerals. Electrochemical reduction of MnO2 was studied using electroplated SS. Plated MnO2 was reduced amperometrically. The process was interrupted at different reduction stages, XPS analysis of remaining oxides showed that MnO2 was reduced through MnOOH to Mn2+. We conclude that biomineralized MnO2 may increase corrosion rates by serving as cathodic reactant. (C) 2000 Elsevier Science Ltd. All rights reserved.