Inhibitive effect of 4- and 5-carboxybenzotriazole on copper corrosion in acidic sulphate and hydrogen sulphide solutions

Corrosion inhibitors are often applied to copper, and a number of organic azoles have been used in this regard. It has been shown that a mixture of 4- and 5- carboxybenzotriazole (4-CBT and 5-CBT) forms a superior anti-tarnishing film compared to that derived from benzotriazole (BTAH). This work examines the effect of 4- and 5-CBT, taken individually and not as a mixture, on the corrosion behaviour of copper in aerated acidic sulphate solutions and in an aqueous sulpidising environment. Coupons of pure copper (99.9%) were used in the experimental procedures, which included gravimmetric measurements, polarisation measurements, tarnish and cathodic reduction tests, and FT-Raman and SERS measurements. It was found that both isomers have anti-tarnishing properties, 5-CBT being the superior performer. The inhibition efficiency of each isomer is pH, concentration and time dependent. (Abstract quotes from original text)