Novel surfactants incorporated with 1,3,5-triethanolhexahydro-1,3,5-triazine moiety as corrosion inhibitors for carbon steel in hydrochloric acid: Electrochemical and quantum chemical investigations

The main objective of this work was to examine the corrosion inhibition ability of three novel surfactant molecules synthesized from 1,3,5-triethanolhexahydro-1,3,5-triazine, which named (I, II and III). The chemical structure of these surfactants was confirmed by FT-IR and ¹H NMR spectroscopy. Also the surface active properties for the synthesized compounds were calculated. The effect of these surfactants on carbon steel in a solution of 1 M HCl was studied using mass-loss and electrochemical measurements. Protection efficiencies were found to be 93.1%, 90.7%, and 87% for III, II, and I, respectively. The order of increasing inhibition efficiency was correlated with increasing the number of ethylene oxide units. Potentiodynamic polarization curves indicated that the prepared surfactants acted as mixed type inhibitors. Adsorption of the inhibitor obeys the Langmuir isotherm. Quantum chemical calculations based on ab initio method were performed on I, II and III. The molecular structural parameters, such as the frontier molecular orbital energy HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital), the charge distribution and the fraction of electrons (ΔN) transfer from inhibitor to carbon steel were calculated and discussed.