Experimental and Theoretical Study on the Inhibition Performances of Quinoxaline and Its Derivatives for the Corrosion of Mild Steel in Hydrochloric Acid

The inhibition of mild steel corrosion in 1.0 M HCl solution by quinoxaline and its derivatives were evaluated at 25 °C using weight loss measurement and Tafel polarization technique. These measurements reveal that the inhibition efficiency increased with increase in the concentrations of inhibitors, and the inhibition efficiencies decrease in the order 4-(quinoxalin-2-yl)phenol (PHQX) > 2-quinoxalinethiol (THQX) > 2-chloroquinoxaline (CHQX) > quinoxaline (QX). Tafel polarization curves show that all the investigated inhibitors act as mixed-type inhibitors. Quantum chemical calculation was applied to correlate electronic structure parameters of quinoxaline and its derivatives with their inhibition performances. Molecular dynamics simulations were also used to optimize the equilibrium configurations of the inhibitor molecules on the iron surface. The efficiency order of the studied inhibitors obtained by experimental results was verified by theoretical calculations.