Interfacial adsorption mechanism of hydroxycinnamic acids on iron surfaces: A computational perspective toward eco-friendly corrosion mitigation strategies

Corrosion remains a critical global concern with substantial financial and infrastructural implications. Herein, an in-depth computational exploration of four hydroxycinnamic acids-(HCAs), namely p-coumaric acid-(CMA), caffeic acid-(CFA), ferulic acid-(FRA), and sinapic acid-(SPA) was conducted. Using SCC-DFTB, MD simulation, and quantum chemical calculations, structural and electronic properties of biomolecules and their interactions with iron surfaces were probed. The SCC-DFTB simulations revealed a pronounced tendency of HCAs to form coordination bonds with iron atoms, facilitated by significant hybridization between the orbitals of HCAs and the unoccupied d-orbitals of iron, as evidenced from the projected density of states analysis. Interestingly, SPA, enhanced by its methoxy groups, displayed the highest negative interaction energy (-2.874 eV), followed by FRA (-2.108 eV), CFA (-1.527 eV), and CMA (-1.058 eV). Consistently, MD simulations validated these findings, demonstrating similar adsorption trends for HCAs under aqueous and vacuum conditions. Further quantum chemical analysis, focusing on global and local reactivity descriptors, provided additional insights into the reactivity, stability, and potential interaction sites of the HCAs. It affirmed that additional hydroxy and methoxy functional groups strongly influenced the reactivity of SPA, FRA, and CFA compared to CMA. These insights highlight potential pathways for addressing material corrosion from an atomic and molecular standpoint.