Theoretical and experimental investigation of chitosan/perillaldehyde Schiff base as a corrosion inhibitor for Q235 carbon steel in acidic medium

Herein, the eco-friendly corrosion inhibitor Schiff Bases Based on Chitosan has been successfully synthesized, and its new structure was characterized via Fourier transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance (1H NMR). The efficiency of corrosion inhibitors was studied via classic weight loss, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PDP) methods. The studies indicated that the Per/CS corrosion in 1.0 M HCl has mixed-type behavior with inhibition efficiency with 600 mg l-1 reaching 97 % at 25 degrees C. Thermodynamic calculations, such as the equilibrium constant of adsorption (Kads) and the free energy of energy of adsorption (Delta Gads), suggested that Per/CS exhibits a mixed mode of adsorption. The activation energy, enthalpy, and entropy were calculated and discussed. The results indicated the formation of a protective film of Per/CS inhibitor on the Q235 carbon steel surface, which was investigated via various techniques such as scanning electron microscopy (SEM), Water contact angle, and atomic force microscopy. The X-ray photoelectron spectroscopy indicated the existence of Per/CS molecules on the carbon steel surfaces. Quantum chemical calculations, DFT, and Fukui indices were also applied to describe the adsorption mechanism. Adsorption locator and MD simulations were also performed to describe the ability of the Per/CS molecule to adsorb on the Fe (110).