Effect of Pseudomonas fluorescens on the electrochemical behaviour of a single-phase Cu-Sn modern bronze

The corrosion behavior of a modern bronze (12 wt% Sn) is studied during 100 h of exposure to a Pseudomonas fluorescens culture. Bacteria colonization, preferentially occurring in the form of black spots, caused an ennoblement of the open circuit potential and a decrease of the pitting potential. Eriochalcite (CuCl2*2H2O) and Nantokite (CuCl) were found in the micro-pits detected under the biofilm, associated to a local pH decrease. Electrochemical measurements via impedance spectroscopy revealed a decrease of the charge transfer resistance, which is attributed to the bacteria involvement in the process of passive layer development.