New Quinoline Derivatives as Sulfuric Acid Inhibitor’s for Mild Steel

Two newly synthesised Quinoline derivatives, namely 5-((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) were studied as inhibitors for the corrosion of mild steel in 0.5 M sulphuric acid solution has been examined and characterized by weight loss, polarization and electrochemical impedance spectroscopy (EIS). The experimental results reveal that the organic compound has a good inhibiting effect on the mild steel in 0.5 M H2SO4 solution. The protection efficiency increases with increasing inhibitor concentration, but the temperature has hardly effect on the inhibition efficiency of Q-N(CH3)2 and Q-NO2. The adsorption of the inhibitors on the surface of mild steel in a 0.5 M H2SO4 solution was found to obey Langmuir’s adsorption isotherm. Thermodynamic data clearly show that the adsorption mechanism of Q-N(CH3)2 and Q-NO2 on mild steel surface in 0.5 M H2SO4 solution is mainly electrostatic-adsorption. Potentiodynamic polarization studies have shown that Quinoline derivatives acts as a mixed type of inhibitor. Data obtained from EIS studies were analyzed to model inhibition process through appropriate equivalent circuit model. The Scanning Electron Microscope (SEM) images of the corrosion product confirmed the protection offered by the extract on the surface of the metal immersed in both media.