Investigating the Adsorption Mechanism of Paracetamol as a Corrosion Inhibitor on the Iron (110) Plane Using First-Principles Calculations

Introduction and Objectives: Acidic solutions are widely used for acid pickling, removing impurities and contaminants from the surfaces of metal objects in various industries. This process, however, reduces the corrosion resistance of metal. The objective of this study is to assess the application of certain cost-effective pharmaceuticals as eco-friendly corrosion inhibitors to mitigate metal corrosion in acidic environments.Materials and Methods: The adsorption quality and the potential for forming a stable protective layer of paracetamol on the (110) plane of iron have been investigated and analyzed using first-principles calculations based on density functional theory.Results: Given the presence of a benzene ring and hydroxyl and amide functional groups in paracetamol's structure, numerous structural arrangements were created and optimized. Among these, the arrangement where the paracetamol molecule was adsorbed onto the (110) plane via the benzene ring proved to be the most stable, with an adsorption energy of -242 kJ/mol. The sign and magnitude of the calculated adsorption energy suggest that paracetamol is a suitable corrosion inhibitor for iron surface. The projected density of states, charge density difference, Bader charge analysis, and electron localization function for the optimal adsorption state were calculated to evaluate the molecule-surface interaction. Conclusion: These analyses revealed that the hybridization of the d orbitals of the metal atoms and the π orbitals of the benzene ring, forming a back-donation π bond, played a major role in the adsorption of the paracetamol molecule on the iron surface.