Microorganisms were isolated through environmental sampling, which was carried out in the auxiliary fuel in a Twin-Otter aircraft in Antarctic climate conditions. The identification of microorganisms was performed by sequencing of the 16S gene of ribosomal DNA (rDNA), which allowed distinguish a number of bacteria belonging to the genera Staphylococcus, Kocuria, Nosocomiicoccus and Tersicoccus. For all microroganismos, catalase test was positive.
Electrochemical measurements and morphological characterization of the surfaces was performed before, and after, different immersion times (1, 2, 3, 7 and 14 days) in minimum culture media, Twin (MMT), sterile and inoculated with the consortium and also, with each microorganism isolated.
Impedance diagrams for all immersion times showed a capacitive behavior characterized by a single time constant. Although short exposure times no corrosion process was evident, for longer times the resistance of aluminum oxide (Rox) decreased significantly, suggesting the occurrence of corrosion process, possibly mediated by microorganisms. Morphological changes of surfaces exposed to different media were examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM).
The mechanism of corrosion, particularly that associated with Enzyme approach was studied performing potentiostatic measurements pyrocarbon electrodes modified with cobalt phthalocyanine. The latter compound catalyses the reduction of oxygen via two electrons, ie via hydrogen peroxide. Measurements were made in sterile and inoculated media and in the presence of oxygen. Electrochemical results show that the presence of microorganisms significantly alter the mechanism of oxygen reduction, particularly the reduction of oxygen to hydrogen peroxide. This would confirm the mechanism of the enzymatic approach in microbiologically influenced corrosion.