Corrosion inhibition with a perezone-impregnated Mg/Al hydrotalcite coating in AS21 alloy

The effect of perezone concentration and the behavior of the hydrotalcite MgAl coating impregnated with the perezone on the AS21 magnesium alloy were studied using electrochemical impedance spectroscopy (EIS). The results show that the perezone molecule protects the magnesium surface, with the best concentration being 10 ppm. When the inhibitor was impregnated with the hydrotalcite, the corrosion protection was significantly improved, reaching 91.1% inhibition efficiency. In order to elucidate the adsorption mechanism of perezone on magnesium surfaces, density functional theory calculations (DFT) within a cluster approach were carried out. The Pearson's Hard-Soft Acid-Base theoretical framework reveals, by means of several global parameters, a strong interaction between perezone and the metal surface. Two different adsorption modes were studied in deep. The mixed physisorption-chemisorption process was rationalized in terms of the interactions between the organic molecule and the Mg10 magnesium cluster. Perezone molecule is adsorbed by the oxygen atoms of the substituted quinone ring, whereas the physical component can be explained by the electrostatic interactions between them. The metal cluster transferred charge to the corrosion inhibitor molecule is of about 0.507 e. The formation of a protective layer was observed by means of SEM-EDS and explained by the Fukui reactivity indices.