Theoretical Investigation of Benzilic Acid-Based Deep Eutectic Solvents as Efficient Corrosion Inhibitors for Cu(111) and Al(111) Surfaces: DFT and Monte Carlo Simulation Insights.

Corrosion remains a critical challenge in industrial and environmental settings, necessitating the development of efficient and sustainable inhibition strategies. This study explores the anticorrosion potential of novel deep eutectic solvents (DESs) synthesized using benzilic acid as a hydrogen bond donor in combination with various hydrogen bond acceptors: choline chloride (DES1), tetraethylammonium bromide (DES2), tetrapropylammonium bromide (DES3), and tetrabutylammonium hydrogen sulfate (DES4) in a 1:1 molar ratio. Density functional theory (DFT) calculations at the B3LYP/6-311 + + G(d,p) level and Monte Carlo simulations were employed to elucidate their electronic properties and adsorption behavior on Cu(111) and Al(111) surfaces. Key quantum chemical descriptors — including frontier molecular orbitals (HOMO-LUMO energies), energy gaps, molecular electrostatic potential (MEP) surfaces, electron localization function (ELF), reduced density gradient (RDG) scatter plots, and noncovalent interaction (NCI) analyses — were examined to understand their reactivity and interaction mechanisms. Monte Carlo simulations revealed that all DESs exhibit a greater tendency to donate electrons to Cu d-orbitals (Δ E1(Cu) > Δ E2(Cu)), enhancing their inhibitory effectiveness. Interestingly, DES3 exhibited an inverse trend (Δ E1(Al) < Δ E2(Al)), signifying its superior electron donation capability toward aluminum and enhanced inhibition performance. Adsorption energy analyses indicated that DES4 demonstrated the highest adsorption energy, attributed to its ionic nature and strong electrostatic interactions, whereas DES1 exhibited the lowest. Gibbs free energy (Δ G) calculations confirmed spontaneous chemical adsorption on Cu(111), while nonspontaneous adsorption was observed in cathodic processes on Al(111). Notably, DES3 exhibited the strongest adsorption energy (Δ G_ads = − 167.016 kJ/mol), highlighting its exceptional corrosion inhibition efficiency. These findings provide crucial insights into the electronic and adsorption properties of DESs, demonstrating their potential as effective and environmentally sustainable corrosion inhibitors for industrial applications. [ABSTRACT FROM AUTHOR]