The importance of live biofilms in corrosion protection

As observed before, Al 2024 was passive in artificial seawater (AS) in the presence of a protective biofilm of Bacillus subtilis WB600. When antibiotics were added to the AS to kill the bacteria in the biofilm, pitting occurred within a few hours as indicated by characteristic changes in the impedance spectra. The corrosion potential Ecorr decreased at the same time to values observed in sterile AS. Addition of the antibiotics to sterile AS had no effect on corrosion behavior.