Corrosion control using regenerative biofilms on aluminum 2024 and brass in different media

The corrosion behavior of Al 2024-T3 and C26000 brass exposed to artificial seawater and Luria Bertani medium has been studied using electrochemical impedance spectroscopy. Tests were performed in sterile media and in the presence of three strains of bacteria. A Bacillus subtilis biofilm was genetically engineered to produce polyaspartate or polyglutamate, a B. licheniformis biofilm naturally produced the anionic polymer γ-polyglutamate, and E. coli was genetically engineered to produce polyphosphate. A significant reduction of active pit growth rates and an ennoblement of the corrosion potential E_corr were observed for Al 2024 in both media in the presence of the biofilms. The lowest corrosion rates of Al 2024 exposed to LB medium were observed in the presence of the B. subtilis bacterial biofilms producing polyaspartate and the E. coli bacterial biofilm producing polyphosphate in which E_corr was more positive by about 400 mV than in the sterile solution. A significant reduction of corrosion rates and an ennoblement of E_corr were also observed for brass in both media in the presence of the biofilms. Samples exposed in the presence of biofilms remained untarnished and unattacked for time periods exceeding one week, while samples exposed in the sterile solutions were covered with a dark film of corrosion products.