Anodic polarization behavior of copper in aqueous chloride/benzotriazole solutions

Potential-pH equilibria and potentiodynamic polarization studies were used to confirm that formation of CuCl-2 complexes in 1.0M NaCl and 0.1M NaCl solutions produces a range of potentials at which anodic dissolution of copper occurs without formation of oxide. The interaction of benzotriazole (1 g/l) with oxide-free copper surfaces in the chloride solutions was studied by potentiodynamic polarization and potentiostatic techniques. Inhibition of the anodic dissolution reaction was obtained in near-neutral pH solutions and at pH 3.0. Inhibition was ineffective at pH 1.0. The interaction of benzotriazole with oxide-free surfaces, leading to inhibition, was potential- and time-dependent. Also, a limiting potential was observed and predicted above which additions of benzotriazole are ineffective and above which existing inhibiting films cannot undergo spontaneous repair. The results confirm that benzotriazole can interact with oxide-free surfaces to promote corrosion inhibition of copper. The characteristics of the inhibition behavior, including breakdown and pH effects, were consistent with an inhibiting film that formed by adsorption of neutral benzotriazole molecules onto the Cu surface, followed by the adsorption of a thin layer of cuprous benzotriazole in polymeric form.