Experimental and theoretical investigation on adsorption and corrosion inhibition properties of imidazopyridine derivatives on mild steel in hydrochloric acid solution.

Imidazopyridine derivatives, namely 4-methoxy- N-((2-(4-methoxyphenyl) H-imidazo[1,2-a]pyridin-3-yl)methylene)benzenamine (MMPIPB) and 4-chloro- N-((2-(4-methoxyphenyl) H-imidazo[1,2-a]pyridin-3yl)methylene)benzenamine (CMPIPB), were investigated as inhibitors for mild steel corrosion in 15% HCl solution using the weight loss and electrochemical techniques. According to electrochemical impedance spectroscopy studies, MMPIPB and CMPIPB show corrosion inhibition efficiency of 84.8 and 77.2% at 10-ppm concentration and 98.1 and 94.8% at 80-ppm concentration, respectively at 303 K. The corrosion inhibition efficiency of both inhibitors increased with increasing inhibitor concentration and decreased with increasing temperature. The adsorption of both inhibitor molecules on the surface of mild steel obeys Langmuir adsorption isotherm. Polarization studies showed that both studied inhibitors were of mixed type in nature. Electrochemical impedance spectroscopy studies showed that for both inhibitors, the value of charge transfer resistance increased and double-layer capacitance decreased on increasing the concentration of inhibitors. Scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDX), and atomic force microscopy were performed for surface study. The density functional theory was employed for theoretical calculations. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]