Corrosion inhibition of aluminum in hydrochloric acid by pyrazinamide derivatives

The inhibiting action of pyrazinamide derivatives toward the dissolution of aluminum electrode in 1.0 M HCl solution was investigated by weight loss, galvanostatic polarization and electrochemical impedance spectroscopy (EIS) measurements. The percentage inhibition efficiency increases with increasing concentrations of pyrazinamide compounds, and with decreasing temperature. The interpretation of the inhibition due to the adsorption of its compounds on the aluminum surface is according to Temkin's isotherm. The interaction between the pyrazinamide compounds and aluminum ions led to the formation of a stable five membered ring complex through the formation two coordination bonds between the lone pairs of electron of the nitrogen and oxygen donor atoms and Al+3 ion. Conductometric titration proved that the stoichiometry of Al+3/pyrazinamide (M/L) is 1:1. The adsorption of the complex led to slow down the rate of corrosion and improvement of the inhibition process. The addition of KI ameliorates the inhibition efficiency due to the synergistic effect. Some activated thermodynamic parameters are calculated and interpreted. (c) 2016 Elsevier B.V. All rights reserved.