Comparative Study of New Quinoxaline Derivatives Towards Corrosion of Copper in Nitric Acid

The inhibitive effect three quinoxalines derivatives named (2Z)-1-(4-chlorophenyl)-2-[(3E)-3-[2-(4-chlorophenyl)-2-oxoethylidene]-3,4-dihydroquinoxalin-2(1H)-ylidene]ethanone (Q4), (2Z)-2-[(3E)-3( 2-oxo-2-phenylethylidene)-3,4-dihydroquinoxalin-2(1H)-ylidene]-1-phenylethanone (Q5) and (Z)-2-(( E)-3-(2-oxo-2-phenylethylidene)-3,4-dihydroquinoxalin-2(1H)-ylidene)-1-phenylethanone (Q6) on the corrosion of copper in 2 M HNO3 has been investigated at 303 K. The study was carried out using weight loss measurements, potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) methods). Results obtained show that Q4 is the best inhibitor and its inhibition efficiency (E %) increases with the increase of inhibitor concentration and reached up to 90 % for Q4 at 10(-3) M. Potentiodynamic polarisation studies clearly reveal that the presence of inhibitors does not change the mechanism of hydrogen evolution and that they act as mixed inhibitors with predominance at cathodic range.