Study on the Corrosion Inhibition Properties of Quinoxaline Derivatives as Acidizing Corrosion Inhibitors for Mild Steel: Synthesis, Experimental Analysis, and Theoretical Insights

Corrosion of metals leads to significant financial losses and poses substantial risks to human safety. The demand for effective corrosion inhibitors is rising. However, few options are available that are both efficient and water-soluble.

This study investigates the influence of two quinoxaline derivatives, 3-(4-bromostyryl)-1-((8-hydroxyquinolin-5-yl)methyl)quinoxalin-2(1H)-one (BrSQX) and 1-((8-hydroxyquinolin-5-yl)methyl)-3-(4-methylstyryl)quinoxalin-2(1H)-one (MeSQX), on the corrosion of mild steel in a 1.0 M HCl solution. The effectiveness of these inhibitors was assessed through various techniques, including weight loss analysis, potentiodynamic polarization (PP), scanning electron spectroscopy (SEM), and theoretical modeling.

The MeSQX and BrSQX compounds exhibited substantial reductions in corrosion rates of mild steel, with inhibition efficiencies reaching 92% and 89%, respectively, at a concentration of 10⁻³ M. The ranking of their inhibition efficiencies was determined to be: BrSQX < MeSQX. Tafel plots demonstrated that both compounds operate via a mixed inhibitory mechanism. The Langmuir isotherm accurately describes the adsorption behavior of these inhibitors on the steel surface, indicating significant adsorption potential and emphasizing the chemisorption characteristics of their binding. Furthermore, the presence of these organic inhibitors elevated the contact angle, enhancing the hydrophobic properties of the surface and facilitating the formation of a protective layer against corrosion. The data from density functional theory (DFT) and molecular dynamics simulations suggest that both inhibitors adsorb similarly on the metal surface. The values for several chemical descriptors, such as gap energy (ΔE), number of transferred electrons (ΔN₁₁₀), interaction energy (E_interaction), etc. show that both inhibitors adsorb efficiently onto the metal surface, explaining the inhibition mechanism.