The inhibition of corrosion of carbon steel in 1 M HCl by the synthesized ionic liquid 4-
(dimethylamino)-1-(6-methoxy-6-oxohexyl)pyridinium bromide (DMOPB) is performed
by electrochemical, gravimetric techniques and surface analysis techniques. The efficiency
of inhibition increases with the inhibitor concentration and reached 93% at 10–3 M. The
polarization data indicate that the tested inhibitor is a mixed type. The adsorption of the
inhibitor on the surface of the steel in 1 M HCl follows the adsorption isotherm Langmuir.
The study of the effect of temperature (303–333 K) on the behavior of the steel in 1 M
HCl in the absence and presence of 10–3 M of the inhibitor shows that the inhibitory
efficiencies increase with temperature in this studied range. The corresponding activation
parameters in the absence and presence of inhibitor were determined and discussed. The
inhibition efficiency was closely related to orbital energies (EHOMO and ELUMO). The
correlation between quantum parameters and experimental inhibition efficiency has been
validated. Scanning electron microscopy images revealed that the inhibitor formed
protective film on mild steel surface.
Key words: ionic liquid, inhibition, carbon steel, acid, free energy.