First Principles Investigations of Mild Steel Corrosion Inhibition by Dopamine Derivatives in HCl Solution

The inhibitory action of three dopamine derivatives on Fe (110) in 1 m HCl aqueous solution is studied by Density‐functional theory (DFT) calculations combined with Monte Carlo molecular dynamics (MD) simulations. It is found that the predominant forms of these compounds at acid pH adsorb spontaneously onto the mild steel surface as the charge transfer fraction values are positive, and the aromatic rings of these forms approach the Fe (110) surface in parallel. The computed adsorption energy values exceed several hundred kcal mol−1, thereby establishing the efficacy of the proposed dopamine derivatives as inhibitors for mild steel corrosion. To interpret the data, reduced density gradient (RDG) calculations are conducted to analyze the non‐covalent interactions (NCI) between the Fe surface and adsorbed molecules. The results of these analyses show that all proposed inhibitors interact with the surface via electrostatic and van der Waals forces. Besides, the self‐diffusivity coefficient and radial distribution function (RDF) are estimated using dynamic simulations. These calculations reveal that corrosive species ( show low diffusivity values, and therefore reduced migration in the presence of a DA2 inhibitor film, thus leading to the formation of stable protective layers, followed by DA3, while the two forms of DA1 (neutral and protonated) show the highest diffusion values.