abstract
- © 2020 Elsevier B.V.Epicatechin gallate (EG), which is isolated from green tea, has been investigated as a corrosion inhibitor for metallic materials such as bronze in a corrosive solution of 3% NaCl using electrochemical techniques such as electrochemical impedance spectroscopy, polarization curves, and scanning electron microscopy. The results showed that 10 ppm of epicatechin gallate is the best concentration to protect the metallic surface of bronze. The measurements with different immersion times showed that the epicatechin gallate is stable for 28 days, while the adsorption of this compound was found to follow the Langmuir isotherm by a mixed process of physisorption-chemisorption. It was proven by SEM-EDS that the presence of the inhibitor film diminishes the corrosion process. Quantum mechanical calculations showed that the mixed-type adsorption can be rationalized by means of electrostatic interactions between EG and the bronze surface, within physisorption regime, and by covalent bonding, corresponding with chemisorption, through oxygen atoms. Reactivity indices shown that EG molecules provides the bronze surface with a cover almost inert against nucleophilic and electrophilic attacks.