Experimental and quantum chemical studies on corrosion inhibition performance of quinoline derivatives for MS in 1N HCl

The corrosion inhibition effect of two quinoline derivatives, viz, 2-chloro quinoline 3-carbaldehyde (CQC) and (2-chloro-quinoline-3ylmethyl)-p-tolyl-amine (CQA) have been investigated against mild steel (MS) in 1N HCl solution using conventional weight loss, potentiodynamic polarization, linear polarization and electrochemical impedance spectroscopy. The losses in weights of MS samples have proved that both CQC and CQA are efficient inhibitors of corrosion. The mixed mode of inhibition was confirmed by electrochemical polarizations. The results of electrochemical impedance spectroscopy have showed changes in the impedance parameters like charge transfer resistance and double-layer capacitance that confirmed strong adsorption of inhibitors on the MS surface. The inhibition action of these compounds was assumed to occur via adsorption on the steel surface through the active centres contained in the molecules. Furthermore, quantum chemical calculations have been performed at B3LYP/6-31G(d, p) level to complement the experimental evidence.