THE ROLE OF BIOMINERALIZATION IN MICROBIOLOGICALLY INFLUENCED CORROSION

Synthetic iron oxides (goethite, alpha-FeO . OH; hematite, Fe2O3; and ferrihydrite, Fe(OH)(3)) were used as model compounds to simulate the mineralogy of surface films on carbon steel. Dissolution of these oxid es exposed to pure cultures of the metal-reducing bacterium, Shewanell a putrefaciens, was followed by direct atomic absorption spectroscopy measurement of ferrous iron coupled with microscopic analyses using co nfocal laser scanning and environmental scanning electron microscopies . During an 8-day exposure the organism colonized mineral surfaces and reduced solid ferric oxides to soluble ferrous ions. Elemental compos ition, as monitored by energy dispersive x-ray spectroscopy, indicated mineral replacement reactions with both ferrihydrite and goethite as iron reduction occurred. When carbon steel electrodes were exposed to S. putrefaciens, microbiologically influenced corrosion was demonstrat ed electrochemically and microscopically.