The inhibition performance of Acacia mearnsii bark tannin was investigated as ecofriendly 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. K E Y W O R D SAcacia mearnsii tannin, aluminum alloy, green corrosion inhibitor

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The inhibitive behavior of Quebracho tannin extract on SAE 1010 steel corrosion in the acidic media is investigated. Potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM) are first used to determine the inhibition efficiency of Quebracho in 0.1 M HCl solution to identify the best extract concentration to subsequently evaluate the inhibitor activity in CO2‐rich aqueous solution at high pressure (15 MPa) and high temperature (70°C). Polarization curves revealed that Quebracho extract acted as cathodic inhibitor and that the inhibition efficiency is dependent on the extract concentration. The EIS measurements and SEM analysis showed that the inhibitor had been adsorbed on the steel surface. The inhibition efficiency of Quebracho in CO2 medium was similar to the 0.1 M HCl, reducing expressively the corrosion rate. The SEM images and X‐ray diffraction analysis showed that iron carbonate was the main corrosion product formed on the metal surface in CO2‐rich environment in the presence of Quebracho. Besides, the corrosion scale was thinner and more compact in the presence of inhibitor.

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