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

Abstract

Bio®lms 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) identi®ed MnO 2 within these bio®lms. Field exposed SS showed similar ennoblement after 30 days. XPS analysis of these samples revealed a mixture of dierent manganese minerals. Electrochemical reduction of MnO 2 was studied using electroplated SS. Plated MnO 2 was reduced amperometrically. The process was interrupted at dierent reduction stages. XPS analysis of remaining oxides showed that MnO 2 was reduced through MnOOH to Mn 2+. We conclude that biomineralized MnO 2 may increase corrosion rates by serving as a cathodic reactant.

Electrochemical techniques used in MIC studies

“…Other than this, Tafel polarization technique can also be used to study the dynamics changes of anodic and cathodic reaction caused by microorganisms or biofilm. Some studies showed that the biofilm formed in seawater can increase the depolarization in the cathodic curve 15,16].…”

Microbiological Corrosion of Metallic Materials

“…The MnO 2 can also be reduced to Mn 2 þ by accepting two electrons from metal dissolution. The intermediate product is MnOOH [52].…”

The use of electrochemical techniques for the investigation and monitoring of microbiologically influenced corrosion and its inhibition – a review

“…Results by Linhardt [20,21] and Lewandowski et al [8,22] present a special case of ennoblement observed for SS in river waters involving formation of MnO 2 . Linhardt [20,21] found large amounts of manganese minerals (mainly MnOOH and MnO 2 ) on severely pitted SS turbine runner blades in a hydroelectric plant and suggested that pitting was due to ennoblement caused by biomineralized Mn oxides.…”

“…Johnsen and Bardal suggested that ennoblement was due to a change of the cathodic properties of the stainless steels as a result of microbial activity on the surface [7]. While it has been accepted that microbial colonization is responsible for ennoblement, a number of different explanations have been offered [8] that include microbial production of extracellular substances [9], organometallic complexes [7] or specific enzymes [10].…”