Manganese oxides deposited by biofilms of Leptothrix discophora SP-6 on 316L stainless steel corrosion coupons increased the open circuit potential of the steel to values of +375 mVSCE. XPS spectra of the deposits compared to spectra of different manganese containing minerals indicated that the deposits were composed of MnO2. The redox reaction responsible for the potential change results in electron transfer from the metal substratum to the mineral deposit. To study the processes of manganese dioxide reduction, MnO2 which had been electroplated on stainless steel was reduced electrochemically. The surface chemistry before and after reduction was analyzed by XPS. We demonstrated that the manganese dioxide deposited on stainless steel coupons can be reduced to Mn2+ by accepting two electrons from the metal. MnOOH was identified as an unstable intermediate product in this reaction. Consequently we hypothesize, that manganese dioxide microbially deposited on stainless steel surfaces can provide an efficient cathodic reaction and accelerate microbially influenced corrosion processes.

Subject
Steel surfaces, Oxides, Minerals, Manganese, X-ray spectroscopy, Biofilms, Surface analysis, Metals, Ennoblement, Corrosion coupons, Deposit corrosion, Stainless steel, Risk reduction
Keywords:
manganese oxidizing bacteria (MOB), Leptothrix discophora SP-6, biofilm, mineral deposit, biomineralization, manganese dioxide, corrosion, ennoblement, 316L stainless steel, surface analysis
Government work published by the Association for Materials Protection and Performance (AMPP) with permission of the author(s). Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
1998
GOV
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