An electrochemical and SERS investigation on the influence of pH on the effectiveness of some corrosion inhibitors of copper

The adsorption on Cu of the corrosion inhibitors benzotriazole (BTA), 2-mercaptobenzothiazole, 2-mercaptobenzimidazole and 2-mercaptobenzoxazole has been characterized in both neutral and acid chloride solutions using electrochemical techniques and surface enhanced Raman spectroscopy. The undissociated inhibitors and their anions are adsorbed simultaneously, the surface concentration ratio depending on the pH and electrode potential. At low pH, BTA is adsorbed weakly and it is displaced from surface sites by both Cl- and the strongly adsorbed 2-mercaptobenzothiazole. These spectroscopic results explain the low corrosion inhibition due to BTA in acid solution.