Inhibition of flash rusting of HY80 by a mussel adhesive protein: Characterizing the interaction of MeFP-5 with a high strength low alloy steel

Abstract

A proteinaceous biopolymer, mussel adhesive protein #5 (MeFP-5), isolated from the common blue mussel (Mytilus edulis L) has been investigated as a model for designing an aqueously soluble candidate corrosion inhibitor system that is non-toxic and environmentally friendly and is capable of inhibiting the flash rusting of exposed high strength low alloy (HSLA) steel surfaces during the paint removal process. In a previous study it was found that a significant amount of corrosion inhibition is possible (nearly 100% inhibition after 7 days) on HY80 steel in a 100% relative humidity environment at 40 °C. In an attempt to determine the possible mechanisms of corrosion inhibition, surface characterization of HY80 steel treated with various solutions containing the MeFP-5 biopolymer were performed. Fourier transform infrared (FT-IR) spectroscopy using attenuated total reflectance (ATR) of the protein adsorbed onto glass and metal surfaces indicated that complexation of the iron atoms on the oxyhydroxide covered metal surface involved the amino acid l-dopa and the primary amine of lysine. The involvement of these amino acids in the adsorption of the protein onto glass were much less evident. When the adsorbed protein was treated with a catechol oxidase enzyme, vibration bands consistent with metal complex formation involving l-dopa were not observed, indicating that the treatment with enzyme resulted in mess metal chelation at the surface oxide-protein film interface. Energy dispersive x-ray spectroscopy (EDS) findings indicate that iron content is highest where the MeFP-5 biopolymer is adsorbed onto the steel substrate at pH 5.5, 50% higher than the content of the iron on the steel surface alone. When the biopolymer is enzymatically cross-linked on the steel surface at pH 5.5, the iron content is decreased by 15% of that of the adsorbed biopolymer, suggesting that the iron at the steel surface is undergoing complexation and possible metal-mediated cross-linking, whereas the enzyme cross-linked protein on the steel surface complexes less of the iron. Three-dimensional modeling efforts of MeFP-5 suggest that specific domains of MeFP-5 where two amino acids, l-Dopa and lysine, are concentrated may be involved in adsorption to a metal oxyhydroxide film. These results indicate that it is possible to utilize the biochemistry of a naturally occurring biopolymer isolated from the marine mussel, Mytilus edulis (L), to develop a non-toxic and environmentally friendly corrosion inhibitor.