Corrosion Inhibition of Copper by 2-Mercaptobenzothiazole and Benzotriazole in Low-Conductivity Solutions

Corrosion inhibition of copper in a low-conductivity medium ( < 10 μS cm−1) containing benzotriazole (BTA) and/or 2-mercatobenzothiazole (MBT) was studied by using the AC impedance technique, Auger electron spectroscopy and corrosion tests. As the MBT concentration increased, the corrosion rate of copper abruptly rose to a peak, rapidly fell, and then finally decreased steadily. The maximum corrosion rate appeared at a MBT concentration of about 0.5 ppm. However, a concentration of more than 1.5 ppm MBT could effectively inhibit copper corrosion. The results from AC impedance measurements agreed with those from corrosion tests. The film resistance could be observed only when the MBT concentration was in excess of 1.5 ppm. A combination of BTA and MBT proved to be more effective than either compound used alone.