CORROSION INHIBITION OF ALUMINUM IN 0.1 M HCL SOLUTION BY GLUTAMIC ACID

Abstract

The inhibition effect of glutamic acid (Glu) on corrosion of aluminum in 0.1 M HCl solution was investigated using linear polarization (LPR), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) methods. Polarization curves revealed that Glu acted as a mixed-type inhibitor. The values of polarization resistance obtained by LPR and EIS were consistent in showing that inhibition efficiency increased with increasing concentration of Glu. The inhibition occurs by adsorption of Glu on the metal surface, and evidence of this was given by the equivalent circuit analysis of EIS results. The adsorption process was found to obey the Hill-de Boer isotherm with a standard free energy of adsorption of −60.45 kJ mol−1. Surface analysis by means of X-ray photoelectron spectroscopy (XPS) was performed to provide chemical characterization of the adsorbed layer. The N 1 s spectrum showed the presence of ionized () and neutral (NH2) amino group. The corrosion inhibition was attributed to a chemisorption process with Glu molecules forming a stable chelate on the metal surface.