Quinoxaline Derivatives as Newly Acid Corrosion Inhibitors for Mild Steel: Synthesis, Electrochemical, and Theoretical Investigations

The inhibition effect of novel quinoxaline-derived compounds (Q3 and Q4) on the corrosion of mild steel in 1.0 M HCl solution was studied using gravimetry, potentiodynamic polarization and electrochemical impedance spectroscopy. The impact of temperature and inhibitor concentration was studied to illustrate the mechanism of inhibition. The data showed that quinoxaline derivatives (Q3 and Q4) are good inhibitors of mild steel corrosion in 1.0 M HCl solution. The inhibition is based on the adsorption of the steel into the HCl solution. The inhibition is based on adsorption phenomena, which is consistent with the Langmuir adsorption model. The inhibition efficiency increases with the concentration of Q3 and Q4 to reach a maximum value of 96.9% and 95.7%, respectively, at 0.001 M and 25 °C. Potentiodynamic polarization data confirmed that quinoxaline derivatives behave as a mixed-type inhibitor. Thermodynamic parameters indicate that both quinoxaline compounds (Q3 and Q4) are adsorbed on the steel surface due to the Langmuir isotherm. DFT calculations and DM simulations were performed on the quinoxaline-derived inhibitor to correlate with the experimental data. The results obtained by the different methods are in good agreement.