Theoretical study of novel antipyrine derivatives as promising corrosion inhibitors for mild steel in an acidic environment

The research delved into studying the anti-corrosive capabilities of newly developed antipyrine derivatives for mild steel in an acidic environment through density functional theory (DFT) and molecular dynamic (MD) simulation. The results of DFT calculations indicated that the newly designed antipyrine molecules exhibited high E_HOMO (− 4.788, − 4.908, and − 4.942) and low E_LUMO (− 2.339, − 3.109, and − 3.101) and energy gap (2.449, 1.799, and 1.841) for compound A1, A2, and A3, respectively. This suggests their propensity to transfer and accept electrons during molecular interaction with the alloy surface, promoting adsorption and corrosion protection. The antipyrine molecules were also noted to contain numerous electron-rich sites around the heteroatoms, functional groups, and inherent aromatic rings within their structures which helps in facilitating molecular interaction with the metal, leading to the adsorption, and formation of a protective layer for effective corrosion protection. High AlogP values (3.74 to 5.00) strongly indicate the molecules' hydrophilic nature, coating ability, and propensity to disperse water molecules and chloride ions in the corrosive system. The MD simulations also revealed high energy of adsorption, which follows a decreasing trend of A2 (− 161.00 kcal⋅mol⁻¹) > A1 (− 157.15 kcal⋅mol⁻¹) > A3 (− 107.93 kcal⋅mol⁻¹) indicating strong and spontaneous adsorption with a flat orientation on the Fe(110) surface. The radial distribution function (RDF) results further supported the chemosorption nature of the inhibitor molecule, and the formation of robust bonds with Fe(110) with all calculated RDF values falling below 3.5 Å. Inclusively, the investigated antipyrine compounds exhibited strong anti-corrosive properties, positioning them as promising corrosion inhibitors for mild steel deployed in acidic environments.