SERS AND IMPEDANCE STUDY OF THE EQUILIBRIUM BETWEEN COMPLEX-FORMATION AND ADSORPTION OF BENZOTRIAZOLE AND 4-HYDROXYBENZOTRIAZOLE ON A COPPER ELECTRODE IN SULFATE-SOLUTIONS

The corrosion inhibition mechanism of benzotriazole and 4-hydroxybenzotriazole for copper in sulphate solutions was investigated by SERS spectroscopy and impedance measurements. These inhibitors form complex polymers on the copper surface at high pH of the solution, positive potential of the electrode, and high concentration of the inhibitors. At low solution pH, negative electrode potential and low inhibitor concentration, single molecules of the inhibitors are adsorbed chemically on copper. Equilibrium between the complex formation and the adsorption relates strongly with the corrosion inhibition effect. 4-Hydroxybenzotriazole shows a higher inhibition efficiency at the high solution pH than benzotriazole, at low pH values this order is reversed. © 1990.