The effect of some Schiff bases on the corrosion of aluminum in hydrochloric acid solution

The inhibition effect of Schiff bases benzylidene-(2-methoxy-phenyl)-amine (A), (2-methoxy-phenyl)-(4-methyl-benzylidene)-amine (B), (4-chloro-benzylidene)-(2-methoxy-phenyl)-amine (C) and (4-nitro-bezylidene)-(2-methoxy-phenyl)-amine (D) on the corrosion of aluminum in 1 M HCl has been studied by polarization, electrochemical impedance spectroscopy (EIS) and weight loss measurements. It has been found that all the studied Schiff bases are excellent inhibitors. Maximum inhibition was obtained for 0.01 M Schiff base A. Results show that the inhibition efficiency increases with decreasing in temperature and increasing in concentration of Schiff base. Polarization curves reveal that the used inhibitors are mixed type inhibitors. The surface adsorption of the Schiff bases leads to a decrease of double,layer capacitance as well as an increase of polarization resistance. The inhibitor performance depends strongly on the type of function groups substituted on benzene ring. The adsorption of used compounds on the aluminum surface obeys a Langmuir isotherm and has a physical mechanism. Thermodynamic parameters for both dissolution and adsorption processes were determined. The quantum chemical study of the corrosion inhibition efficiency of the Schiff bases on Al in molar HCl was carried out. (c) 2005 Elsevier B.V. All rights reserved.