Some Triazolic Compounds as Corrosion Inhibitors for Copper in Sulphuric Acid

Corrosion inhibition of copper in 1.0 M H2SO4 was investigated in the absence and presence of different concentrations of triazole derivatives namely, 1, 2, 4-triazole (TR), 3-amino-1, 2, 4-triazole (ATA) and 2-4-diamino-1, 2, 4-triazole (DTA). Weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements were employed. Impedance measurements showed that the charge transfer resistance increased and double layer capacitance decreased with increase in the presence of these inhibitors. Potentiodynamic polarization reveal that compound DTA is the best inhibitor and the inhibition efficiency (IE %) follows the sequence: DTA greater than ATA greater than TR. Obvious correlations were found between corrosion inhibition efficiency and some quantum chemical parameters such as energy of highest occupied molecular orbital (HOMO), energy of lowest unoccupied molecular orbital (LUMO), HOMOLUMO energy gap and electronic density etc. Calculated results indicated that the difference in inhibition efficiencies between these compounds can be clearly explained in terms of frontier molecular orbital theory. The inhibitor performance depends mainly on the type of function groups substituted on triazole ring.