Synthesis, characterization and corrosion inhibition of 1-(4-anisyl)-3-(4-(pyridin-4-ylmethyl)phenyl)carbamide on mild steel in 1M HCl: A comprehensive study from experimental, theoretical and microscopic modelling perspectives

Abstract

In the present study, a novel, cost-effective organic corrosion inhibitor, 1-(4-anisyl)-3-(4-(pyridin-4-ylmethyl)phenyl)carbamide (U–OCH₃), was synthesized and characterized by spectroscopic techniques. The corrosion inhibition properties of U–OCH₃ against mild steel (MS) in 1 M HCl medium were evaluated through weight loss measurements, electrochemical tests, surface analysis, and theoretical calculations. The experimental results demonstrated that 200 ppm of U–OCH₃ exhibits excellent corrosion inhibition, with a high inhibition efficiency of 98.62 % at 303 K, though its effectiveness decreases with increasing temperature. Kinetic and thermodynamic analyses suggested that U–OCH₃ inhibits corrosion through physisorption, with a mixed-type inhibitive action that adheres to Langmuir's adsorption isotherm. Surface analysis using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Analysis (EDX), Atomic Force Microscopy (AFM), and X-ray Photoelectron Spectroscopy (XPS) confirmed the formation of a thin inhibitor film, which adsorbs onto the steel surface via interactions with the heteroatoms (pyridine and phenyl rings) in U–OCH₃. Density Functional Theory (DFT) calculations revealed a strong correlation between the inhibitor's molecular structure and efficacy. Fukui index analysis identified specific attack sites on the metal surface. At the same time, Molecular Dynamics Simulations (MDS) provided insights into the interaction energies between the inhibitor and the steel surface, further validated by Radial Distribution Function (RDF) measurements. The study also assessed the self-diffusion coefficient, fractional free volume (FFV), and interactions between the inhibitor film and corrosive species, with experimental results aligning closely with theoretical predictions.