Tetrahydropyrimido-Triazepine derivatives as anti-corrosion additives for acid corrosion: Chemical, electrochemical, surface and theoretical studies

[Display omitted] •Polarization studies revealed the mixed type behavior for these molecules.•The adsorption of both inhibitors obeys Langmuir adsorption isotherm and surface morphology was examined by SEM and UV-visible.•Quantum chemical studies further support the experimental findings. The inhibition efficiency (IE) of 4-hydroxy-8-isocyano-9-phenyl-3-(p-tolyl)-1,2-dihydropyrimido[2,1-c][1,2,4]triazepine-5,7-dione (TRC-H) and 9-(4-chlorophenyl)-4-hydroxy-8-isocyano-3-(p-tolyl)-1,2-dihydropyrimido[2,1-c][1,2,4]triazepine-5,7-dione (TRC-Cl) on the mild steel (MS) corrosion in 1 M HCl acid was studied by weight loss, electrochemical (EIS and PDP) techniques, DFT, molecular dynamic (MD) simulations, radial distribution function (RDF) and mean square displacement (MSD). TRC-H and TRC-Cl effect on the surface of MS has even been accentuated by scanning electron microscopy (SEM) and UV–visible. The adsorption on the steel is made according to the Langmuir model. Molecular dynamics simulation (MD) and Density Functional calculations were done to discussing their agreement with previously experimented results.