Effect of Blends of Benzotriazole and Thiourea on the Anodic Dissolution of Copper

Abstract

The blending of benzotriazole (BTAH) and thiourea (TU) was shown to exert synergistic or antagonistic effects on the anodic dissolution of copper at pH ≈ 1.8 depending on their concentrations in the blend. While synergism was observed in blends with low concentrations of TU and BTAH, antagonism was observed in blends containing higher, i.e. ≥ 10 −2 M, concentrations of TU to an extent which increased with the concentration of TU. The antagonistic effect of TU was discussed in the light of its tendency to produce hydrogen sulphide which promotes the anodic dissolution of copper. Analysis of the adsorption behaviour of the individual compounds using the Langmuir isotherm revealed stronger interaction of the copper surface with BTAH than with TU, as judged by free energy of adsorption values of −18.8 and −8.7 kJ/mol for BTAH and TU, respectively.