A combined experimental and theoretical study of green corrosion inhibition of bronze B66 in 3% NaCl solution by Aloe saponaria (syn. Aloe maculata) tannin extract

Abstract

Since antiquity, bronzes have been one of the main cultural heritage metallic artifacts. Currently, they continue to have many applications in various industrial fields. Nevertheless, bronzes are subject to the corrosion process in aggressive environments containing chlorides. To overcome this destructive phenomenon, various conventional protection inhibitors have been developed. Unfortunately, these prevention inhibitors have serious drawbacks are expensive and harmful to human health and the environment. Plant extracts are one of the alternatives that can be used as an ecological, cost-effective and efficient alternative. In this context, Aloe saponaria tannin (AST) extract has been tested as green corrosion inhibitor for bronze B66 in 3% NaCl. The experimental study was conducted by gravimetric and electrochemical measurements, supplemented by surface analysis scanning electron microscopy (SEM) coupled to energy dispersive X-ray spectroscopy (EDX). Which allowed us to highlight the protective effect of our inhibitor. In addition, to investigate the adsorption action of AST compounds over the bronze surface, the theoretical simulations based on the MD (molecular dynamics) and DFT (density functional theory) were done. The electrochemical measurements confirmed the results obtained from the gravimetric measurements and noted that the effect of our inhibitors alters the mechanism of the electrochemical process at the metal/solution interface. The experimental results obtained allowed to note that the AST compounds act as a cathodic type inhibitor. Then, the maximal inhibition efficiency reaches 90% at 150 ​ppm of AST extract. Moreover, the results of theoretical modeling studies supported the adsorption of AST molecules on the target metal substrate.