Corrosion inhibition properties of small peptides: DFT and Monte Carlo simulation studies

Abstract

Using the computational methods of Density Functional Theory (DFT) and Monte Carlo (MC), we investigated the potential and mechanism of corrosion inhibition of iron, copper and aluminum by small peptides of aliphatic amino acids (AAs), such as L-alanine (Ala) dipeptide and tripeptide. The article provides an assessment of the local and global descriptors of the reactivity of Ala in neutral and protonated forms and its changes when combining Ala into di- and tripeptides. There was established a boost in the inhibitory effect of di- and tripeptides, due to an increase in the number of reaction centers of the molecular structure. The authors calculated the adsorption energies, and determined the most stable low energy configurations for the adsorption of alanine amino acids and small peptides on Fe (110), Cu (111), and Al (111) surfaces. It has been established that Ala and Ala-derived peptides can be absorbed on these substrates by chemisorption, predominantly located on epitaxial grooves. The absolute values of the adsorption energy between these inhibitors on the studied metal surfaces rise with an increase in the number of amino acid residues. The stronger adsorption of small peptides is also indicated by a decrease in the shortest bond lengths between the layer of on-surface Fe, Cu and Al atoms and the nearest inhibitor atoms that are characterized by the following sequence: Ala > Ala-Ala > Ala-Ala-Ala. The peptides have the best adsorption ability to the iron surface, which characterizes their highest inhibitory efficiency from a theoretical point of view. The results of the studies performed have demonstrated promising prospects for the use of small peptides as effective “green” corrosion inhibitors.