Adsorption and corrosion inhibition performance of some environmental friendly organic inhibitors for mild steel in HCl solution via experimental and theoretical study

Abstract In this study, two organic compounds were synthesized: N-[(2E)-3-phenylprop-2-en-1-yl]aniline (PPA-1) and 4-{[(2E)-3-phenylprop-2-en-1-yl]amino}phenol (PPAP-2). Their structures were confirmed by DRIFT, 1H and 13C NMR spectroscopy analyses. The two organic molecules were inspected as corrosion inhibitors of mild steel in HCl medium. The experimental studies such as electrochemical impedance spectroscopy, potentiodynamic polarization and surface analysis were conducted in order to prove the corrosion inhibition of these molecules and to confirm the presence of the organic film on the mild steel surface. Furthermore, theoretical studies by density functional theory and molecular dynamic simulation were used to corroborate the electrochemical results and to establish the adsorption mechanism and the orientation of the two organic molecules at the interface mild steel-aggressive solution. Langmuir adsorption isotherm model was used to explain the adsorption of the two molecules in HCl solution. Mulliken charges, Fukui functions, proton affinity and gas-phase basicity indicate that the nitrogen and oxygen heteroatoms are the most basic active site. Molecular dynamics simulation showed that the two inhibitors were adsorbed almost parallel on the Fe (110) surface attesting the high inhibition performances.