Experimental Study for the Influence of Methyl Substituent's Position on Quinoline for Inhibition of Aluminium Corrosion in Hydrochloric Acid

Some selected methylquinolines' performance on inhibition of Aluminum (Al) corrosion and the effect of methyl group at 5,7 and 8 on quinoline investigated in hydrochloric acid experimentally through weight loss, EIS (Impedance Measurement ) and PDP (Potentiodynamic Polarization). For weight loss, five-methyl quinoline (5-MeQ), seven-methyl quinoline (7-MeQ) and eight-methyl quinoline (8-MeQ) were used in varying mass and temperature in different concentrations of HCl. The adsorption characteristics of these inhibitors were found to be consistent with Langmuir isotherm; both physical and chemical mechanisms played a significant role. Comparatively, the rate of corrosion, mass loss, inhibition effectiveness, and the degree of surface coverage obtained from the weight loss indicated the superiority of 5-MeQ performance over 7-MeQ and 8-MeQ. The eight-methyl quinoline has the least corrosion inhibition performance under the same conditions. The speed of the inhibition process was found to follow first-order kinetics for all the systems. The surface morphology and the functional group before and after the corrosion were investigated through SEM and FTIR analysis. The Nyquist plot from impedance data and the parameters also indicated the same behaviour as the weight loss. The Tafel plot polarization data and the parameters show the same trends. The results of the EIS. and PDP are found to be relatively consistent with that of weight loss. All the molecules showed outstanding corrosion inhibition efficiency. However, the 5-MeQ molecule gives better Al corrosion inhibition than the other two molecules.