Tannin of Acacia mearnsii as green corrosion inhibitor for AA7075-T6 alluminum alloy in acidic medium

The inhibition performance of Acacia mearnsii bark tannin was investigated as eco-friendly green inhibitor on the corrosion of AA7075-T6 aluminum alloy in 0.1 M HCl solution by potentiodynamic polarization technique, electrochemical impedance spectroscopy (EIS) and scanning electron microcopy (SEM). Polarization curves showed that this tannin acts predominantly as a cathodic inhibitor. High corrosion inhibition performance was achieved with inhibition efficiencies of 95% and 97% at 14 g L-1 as obtained by polarization and EIS electrochemical techniques, respectively. The SEM images revealed that localized attack initiated at intermetallic particles causing local dissolution of the matrix due to potential differences between them. EIS results and SEM images confirmed the protection of AA7075-T6 aluminum alloy by A. mearnsii bark tannin, evidencing the formation of an adsorbed film on the metal surface that attenuate the aluminum dissolution reaction.