Adsorption Behavior of Glucosamine-Based, Pyrimidine-Fused Heterocycles as Green Corrosion Inhibitors for Mild Steel: Experimental and Theoretical Studies

Effects of electron donating (−CH3 and −OH) and electron withdrawing (−NO2) substituents on the corrosion inhibition efficiency of four glucosamine-based, substituted, pyrimidine-fused heterocycles (CARBs) on mild steel corrosion in 1 M HCl have been investigated using gravimetric, electrochemical, surface morphology (SEM, AFM, and EDX), and computational techniques. Gravimetric studies showed that protection performances of the compounds increase with increase in concentration. Both electron withdrawing (−NO2) and electron donating (−CH3 and −OH) groups were found to enhance the inhibition efficiency, but the effect is more pronounced with electron-donating substituents. The compounds were found to be cathodic-type inhibitors as inferred from the results of potentiodynamic polarization studies. EIS studies suggested that the studied compounds inhibit metallic corrosion by adsorbing on metallic surface. The adsorption of the inhibitor molecules on steel surface was further supported by SEM, AFM, and EDX analyses. Adsorption of CARBs on a mild steel surface obeyed the Langmuir adsorption isotherm. Theoretical studies using quantum chemical calculations and molecular dynamics simulations provided additional insights into the roles of the −OH, −CH3, and −NO2 substituents on the corrosion inhibition performances of the studied inhibitors.

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