Inhibition of Copper Corrosion in 3.0% NaCl Solution by N-Phenyl-1,4-phenylenediamine

Inhibition of copper corrosion by N-phenyl-1,4-phenylenediamine (NPPD) has been investigated in deaerated, aerated, and oxygenated aqueous 3.0% NaCl solutions using potentiodynamic polarization, electrochemical impedance spectroscopy, weight loss, infrared and UV-visible absorption spectroscopic, scanning electron microscopic (SEM), and energy-dispersive X-ray (EDX) measurements. Potentiodynamic polarization measurements showed that the presence of NPPD significantly decreases cathodic, anodic, and corrosion currents in these solutions. Impedance measurements indicated that the charge-transfer resistances increase upon increasing the NPPD concentration. The inhibition efficiency of 1.0 mM NPPD obtained by weight-loss measurements is about 90%, increasing to about 96% at its concentration of 5.0 mM. Fourier transform infrared, UV-visible, SEM, and EDX measurements revealed that NPPD is adsorbed on the copper surface at open-circuit potentials, preventing copper from being corroded by forming a protective layer on its surface. All these results showed that corrosion of copper decreases in the order of oxygenated > aerated > deaerated solutions, and NPPD is a good mixed-type inhibitor for copper corrosion with its inhibition efficiency in the order of oxygenated > aerated > deaerated solutions.