Novel thiazole-derived Schiff-Bases as efficient corrosion inhibitors for mild steel in acidic Media: Synthesis, electrochemical and Computational insights

Abstract

Novel thiazole-derived Schiff bases 3a-c have been synthesized via thermal as well as microwave assisted condensation of 2,4-dihydroxybenzaldehyde and aminothiazole derivatives in an ethanolic solution containing catalytic amounts of acetic acid. The structure of the synthesized thiazole-based Schiff bases was elucidated by spectroscopic tools as well as their elemental analyses. The efficiency of these compounds in corrosion inhibition was evaluated for mild steel in H2SO4 solution using electrochemical techniques. Studying the behavior of these compounds under various conditions clarified their effectiveness as beneficial corrosion inhibitors. Increasing the concentration of both inhibitors led to higher effectiveness in inhibiting corrosion. The inhibition efficiency (IE) of studied inhibitors was found to increase in the following order; 3c > 3b > 3a. The mechanism of adsorption was suggested based on the Temkin adsorption isotherm, and was found to follow mixed mode of adsorption, with the chemical mode is the prevailing as revealed from the free energy change values. Moreover, the correlation between the inhibition efficiency and the molecular structure of the examined inhibitors was explored through quantum chemical calculations. These calculations demonstrated that the high electron density on the Schiff bases molecule contributes to a high corrosion inhibition efficiency. Additionally, the addition of an electron donor group on the thiazole ring enhanced the molecule’s adsorption ability on the mild steel surface.