Highly Efficient and Water-Soluble Substituted Pyridinyl Ethyl Urea Inhibitors for the Protection of Mild Steel in Acidic Medium: An Experimental, DFT, and Molecular Dynamics Studies

Four novel, potential and water-soluble corrosion inhibitors, namely 1-(4-methyl phenyl)-3-(2-pyridin-2-ylethyl) urea (PTPEU), 1-(2-phenyl ethyl)-3-(2-pyridin-2-ylethyl) urea(PEPEU), 1-(benzyl)-3-(2-pyridin-2-ylethyl) urea(BPEU), and 1-(4-Fluoro phenyl)-3-(2-pyridin-2-ylethyl) urea(FPPEU) were synthesized and characterized for the protection of mild steel in 1 M HCl. The inhibition ability of the inhibitors was evaluated using gravimetric, electrochemical impedance spectroscopy, and potentiodynamic polarization techniques. Overall, all inhibitors provided better protection than the control. PEPEU was the most effective corrosion inhibitor studied. The surface morphology of mild steel specimens inhibited and uninhibited was determined by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), and atomic force microscopy (AFM). AFM, EDX, and SEM studies confirmed the presence of protective films on mild steel surfaces. The influence of temperature on corrosion rate was also studied. The maximum inhibition efficiency of 98.2% was achieved at 303^oK for PEPEU with 100 ppm in the weight loss method. The polarization measurements indicated that all inhibitors displayed mixed inhibitor behavior. The Langmuir adsorption isotherm governed the adsorption process on mild steel surfaces. Additionally, a comprehensive computational study was performed to support the experimental results through Density Functional Theory (DFT) and molecular dynamics simulations (MD). The results suggest that the PEPEU is a promising corrosion inhibitor for mild steel in acidic environments.