Experimental and theoretical studies for mild steel corrosion inhibition in 1 M HCl by two new benzothiazine derivatives

Highlights: •The inhibition efficiencies of tow benzothiazin-3-one derivatives have been studied on mild steel corrosion in 1 M HCl. •The quantum chemical parameters were determined at B3LYP/6-311++G (2d, 2p) level of theory. •Local reactivity has been analyzed by means of Fukui indices which indicate the reactive centers within the molecules. •A good agreement was observed between the theoretical study and experiment. -- Abstract: The inhibition effect of new heterocyclic compounds, namely 2-aryl-benzothiazin-3-one (P1) and 3-aryl-benzothiazin-2-one (P2) on mild steel corrosion in 1 M HCl was investigated using electrochemical measurements. The results indicated that the inhibition efficiency depends on concentration and molecular structure of the investigated compounds. It is also found that the inhibition of P1 is greater than P2. The molecular structure effect on the corrosion inhibition efficiency was investigated using DFT calculations. The structural and electronic parameters were calculated and discussed. The obtained results show that the experimental and theoretical studies agree well and confirm that P1 is the better inhibitor