Submitted to: International Biodeterioration and Biodegradation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/10/2010
Publication Date: N/A
Interpretive Summary: Corrosion is a global problem that affects safety and economics. Polymers from agriculturally important bacteria are utilized as anticorrosive coatings for low carbon stainless steel. Electrochemical analysis provided the corrosion rates (in milli-inch per year) of 29 exopolysaccharides (dextrans) from a common lactic acid bacteria, Leuconostoc mesenteroides. The exopolysaccharides were structurally similar but their corrosion rates were strain specific. The exopolysaccharide coatings were applied using industrial spraying technology with a thickness of 50 nm. The coatings also exhibited limited self-repairing upon damage (scratch) and hydration. As a paint additive, this property may help prevent rapid coating failure and corrosion of metal when paints are damaged.
Technical Abstract: Corrosion is a global issue that affects safety and economics. There is an increasing demand for bio-based polymers for industrial applications and production of polymers by microorganisms is especially attractive. This work reports on the electrochemical and physical properties of 29 strains or fractions of Leuconostoc mesenteroides exopolysaccharides and their suitability as anti-corrosive coatings. Coating the metal substrate (SAE 10101 stainless stell) with exopolysaccharides protected it from corrosion by reducing ionic diffusion rates and maintaining a relatively hydrophobic environment at the substrate/coating interface. The data suggests the kinetics of film deposition are fast (<5 min) and there is little excess (loosely bound) material when hydrated. AFM measurements show thin, 50nm thick coatings that when exposed to water exhibit self-repairing phenomenon. The corrosion protection offered by a film is reported as the corrosion rate calculated from the corrosion current by electrochemical impedance spectroscopy.