Electrochemical and theoretical study of newly quinoline derivatives as a corrosion inhibitors adsorption onmild steel in phosphoric acid media

[Display omitted] •Two synthesized Quinoline cted as efficient corrosion inhibitors.•The adsorption of Q-N(CH3)2 and Q-NO2 on the mild steel surface, in 1.0 M HCl solution, obeys to Langmuir isotherm.•Surface analysis by MEB/EDX shows the existence of a protective layer onto MS surface.•Theoretical calculations showed that both investigated molecules has a strong adhesion to the metal surface. The corrosion inhibition properties of two newly synthesized Quinoline derivatives5-((2-(4-dimethylamino)phenyl-1H-benzo[d]imidazol-1-yl)methyl)quinolin-8-ol (Q-N(CH3)2) and 5-((2-(4-nitrophenyl)-1H-benzo[d]imidazol-1-yl)methyl)quinolin-8-ol (Q-NO2) on mild steel (MS) in 2.0 M H3PO4 solution has been evaluated by weight loss (WL), Tafel polarization and Electrochemical Impedance Spectroscopy (EIS). The experimental findings reveal that these organic compounds performed as good corrosion inhibitors in 2.0 M H3PO4. The inhibition efficiency increased with increasing of quinoline derivatives concentration. The potentiodynamic polarization studies showed that Q-N(CH3)2 and Q-NO2 acts as a mixed type of inhibitors. The EIS studies showed that the charge transfer resistance increases with the inhibitor concentration and the adsorption of Q-N(CH3)2 and Q-NO2 obeys the Langmuir isotherm. Calculated quantum chemical parameters for studies inhibitors in gas and aqueous were further performed using density functional theory (DFT) at B3LYP/6-31G (d,p) to simulate the order of inhibitor’s performance on mild steel surface.