Ennoblement Due to Biofilms: Indicator for Potential Corrosion and Source of Electrical Energy

Ennoblement, a positive shift in corrosion potential, due to biofilm formation is the basis of patents for biofilm monitoring and power generating devices. Ennoblement is a global phenomenon that is routinely cited as a mechanism for microbiologically influenced corrosion of some passive alloys. Increased corrosion is attributed to acceleration of the oxygen reduction reaction via several potential mechanisms that have been debated for decades. Because the phenomenon is predictable and reproducible at specific locations, ennoblement is the basis for patented methods and devices for monitoring biofilm formation and relating ennobled potentials to increased likelihood of corrosion and for evaluating cleaning and biocide treatments. Furthermore, when anodes and cathodes can be separated, as in a microbial fuel cell, biofilm formation on the cathode increases the potential difference between the two and the resulting power output. Most patented fuel cells using metal cathodes do not refer specifically to ennoblement in the disclosures.