Quinoxaline derivatives as corrosion inhibitors of zinc in 1.0 M hydrochloric and sulphuric acid solutions: Adsorption, electrochemical, spectroscopic, and computational studies

The corrosion inhibition properties of and methyl quinoxaline-6-carboxylate (MQ6CA), and quinoxaline-6carboxylic acid (Q6CA) on zinc in 1.0 M HCl and 1.0 M H2SO4 were studied using gravimetric, electrochemical, spectroscopic, and theoretical studies utilizing density functional theory (DFT). Experimental findings reveal that zinc corrodes more in 1.0 M H2SO4 than in 1.0 M HCl and both the studied quinoxalines show good protection efficiency on zinc. The results obtained from the gravimetric analysis indicate that the inhibition efficiency increased with an increase in temperatures and concentration of the inhibitors. The adsorption of the inhibitors followed the Langmuir isotherm, and the thermodynamic and activation parameters were determined and discussed. The electrochemical studies suggested that the studied quinoxalines possess characteristics of mixed type inhibitors but are predominantly cathodic in nature. The Fourier transform infrared spectroscopy confirmed the formation of the inhibitor-Zn2+ complex. Atomic absorption spectroscopy revealed a decrease in the concentration of zinc ions in the presence of the studied inhibitors as compared to the blank solutions. Calculated values of adsorption energies indicated that the adsorption of studied quinoxalines on zinc surface supports a mixed type of adsorption mechanism.