Interfacial Inhibition of Mild Steel Corrosion by Abemaciclib and Abrocitinib in Acidic Media: Insights from Density Functional Theory and Molecular Dynamics Simulations

This study explores the corrosion inhibition potential of two expired pharmaceutical compounds Abrocitinib (ABR) and Abemaciclib (ABM) as sustainable alternatives to conventional steel corrosion inhibitors in acidic environments. Using a synergistic approach that combines density functional theory (DFT) and molecular dynamics (MD) simulations, the electronic, structural, and adsorption behaviours of the inhibitors were comprehensively examined. The computed energy gaps (ΔE) between 0.911 and 0.950 eV, alongside high electrophilicity indices (ω = 3.468–3.560 eV), indicate strong electron-donating capabilities and reactivity toward metal surfaces. ABM demonstrated a superior adsorption energy of −183.322 kcal/mol, suggesting stronger surface interaction and better inhibition performance. Mulliken charge analysis revealed key adsorption centers around nitrogen and oxygen atoms, while radial distribution functions from MD simulations confirmed robust metal-inhibitor interactions and the formation of a stable protective layer. These findings not only demonstrate the feasibility of reusing pharmaceutical waste for corrosion protection but also introduce an environmentally responsible strategy for sustainable corrosion control in acidic industrial applications.