MICROBIAL CORROSION OF METALS EXPOSED TO AIR IN TROPICAL MARINE ENVIRONMENTS

Carbon steel plates were exposed for 12 months to the marine tropical atmosphere of Campeche, located in the southeast corner of the Gulf of Mexico. The corrosion products of steel were analyzed monthly, using scanning electron microscopy aided with energy dispersive spectroscopy (SEM-EDS) and Fourier transform infrared spectroscopy (FTIR). The mai n meteorological parameters and the NaCl and SO2 deposition rates also were recorded monthly. The FTIR and SEM-EDS morphology, compound, and composition studies indicated amorphous oxyhydroxide and lepidocrocit e formed during the first months of exposure. From five to nine months , when relative humidity mean value was 75%, goethite was clearly dete cted. Filaments, channels, and other unusual inorganic morphologies we re observed at the steel samples surfaces having spots of high carbon contents, around 65 wt% by SEM-EDS analysis and FTIR C-O bondings typi cal of organic material. These corrosion products could be associated to microbially induced corrosion activity.