MICROBIAL INFLUENCED CORROSION STUDIES ON AA2024 ALUMINUM ALLOYS

Jet fuel is frequently contaminated with microorganisms that can cause corrosion of fuel tanks. The wing tank bottom and sides are affected by the growth of a biological sludge associated with the condensed water. The behavior of AA2024 aluminum alloy in a culture of one of the principal contaminates, the bacteria Bacillus Licheniformis (BL), is determined. Comparative results of cyclic polarization and electrochemical impedance spectroscopy (EIS) studies are presented on sterile controls and inoculated electrochemical cells. Cyclic polarization results show an electropositive shift in corrosion potential for inoculated cells versus the sterile controls. EIS results show a steady increase in the charge transfer resistance over several weeks for the inoculated cells versus the sterile controls. Analysis suggests these electrochemically measured changes reflect the deposition of a protective biofilm on the alloy's surface which provides inhibition behavior. Surface changes on the alloy, influenced from the formation of a biofilm, are shown from results of scanning electron microscopy with an energy dispersive system (EDS) analysis.