Pitting Corrosion Control of Aluminum 2024 Using Protective Biofilms That Secrete Corrosion Inhibitors

Abstract

The corrosion behavior of Al 2024-T3 (UNS A92024) exposed to artificial seawater (AS) and Luria Bertani (LB) medium has been studied using electrochemical impedance spectroscopy (EIS). Tests were performed in sterile media and in the presence of three different biofilm-forming bacteria: a Bacillus subtilis biofilm that was genetically engineered to produce either polyaspartate or polyglutamate, a Bacillus licheniformis bacterial biofilm that naturally produces γ-polyglutamate, and an Escherichia coli biofilm that was genetically engineered to produce polyphosphate. A significant reduction in active pit growth rates and an ennoblement of the corrosion potential (E_corr) were observed in both media in the presence of these biofilms, which produce corrosion inhibitors. The lowest corrosion rates of Al 2024 exposed to the LB medium were observed in the presence of the B. subtilis bacterial biofilm-producing polyaspartate and the E. coli bacterial biofilm that produced polyphosphate. In the presence of the latter biofilm, E_corr was more positive by ∼400 mV than in the sterile solution.