Synthesis, Characterization and Comparative Study of Functionalized Quinoxaline Derivatives towards Corrosion of Copper in Nitric Acid Medium

Three quinoxalines named ethyl 2-(4-(2-ethoxy-2-oxoethyl)-2-p-tolylquinoxalin-1(4H)-yl)acetate (Q1), 1-[4-acetyl-2-(4-chlorophenyl)quinoxalin-1(4H)-yl]acetone (Q2) and 2-(4-methylphenyl)-1,4-dihydroquinoxaline (Q3) have been newly synthesised and tested as corrosion inhibitors for copper in 2M HNO(3). The investigation has been conducted at 303K using weight loss measurements, potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) methods). The synthesis of quinoxaline functionalized was achieved by using quinoxaline. After purification, the products obtained are characterised using (1)H NMR and (13)C NMR spectroscopy. Results obtained show that Q1 is the best inhibitor and its inhibition efficiency (E %) increases with the increase of inhibitor concentration and reaches up to 97% at 10(-3) M Q1. Potentiodynamic polarisation studies clearly reveal that the presence of inhibitors does not change the mechanism of hydrogen evolution and that they act predominately as cathodic inhibitors.