Environmentally friendly corrosion protection for aluminum using an Acacia mearnsii tannin-based primer

Abstract

This study evaluates the anticorrosive potential of mimosa tannin, a natural extract from Acacia mearnsii bark, on aluminum in neutral chloride environments. Electrochemical techniques, including linear polarization resistance, open circuit potential, and potentiodynamic polarization, quantified its efficacy across varying concentrations in 0.1 M NaCl. Practical application involved formulating a polyvinyl butyral (PVB) wash-primer, comparing its anticorrosive performance against chromate and talc primers. Analyses showed mimosa tannin significantly impedes AA1050 aluminum corrosion, achieving over 95% efficiency even at low concentrations. It exhibited mixed-type inhibitory behavior, suppressing both anodic and cathodic reactions. SEM-EDS and XPS confirmed a dense, protective passive layer on the aluminum surface. Within this layer, tannin molecules integrate, substantially reducing chloride ion adsorption and oxygenated corrosion products, creating a uniform three-dimensional structure. The mimosa tannin PVB primer demonstrated notable anticorrosive properties, significantly outperforming the talc control, though slightly less effective than the chromate primer. Humidity chamber tests further validated its protective capabilities. In conclusion, mimosa tannin offers a compelling, sustainable alternative to traditional chromate-based anticorrosive pigments, providing substantial corrosion protection with reduced environmental impact.