A near-infrared FT-Raman (SERS) and electrochemical study of the synergistic effect of 1-[(1',2'-dicarboxy)ethyl]-benzotriazol and KI on the dissolution of copper in aerated sulfuric acid

The adsorption on copper in aerated 0.5 M sulphuric acid (30 degrees C) of 1-[(1',2'-dicarboxy)ethyl]-benzotriazole (BTM) has been investigated by means of surface enhanced Raman scattering (SERS) techniques. The inhibition efficiency in aerated acid increased with increasing BTM concentration to a maximum (52%) at the 1 x 10(-3) M level. Benzotriazole (BTAH) was found to be about 20% more efficient as an inhibitor for copper corrosion under the same conditions. BTM (1 x 10(-3) M) showed increased inhibition with increasing pH reaching a maximum value of 78.3% at pH 8. Polarization studies showed that BTM suppressed both the cathodic and anodic corrosion reactions. The SERS studies suggest that, like BTAH, BTM inhibits copper corrosion by adsorption through the azole nitrogen. This study also showed that the performance of BTM can be significantly improved by adding KI. SERS indicates that the iodide ions displace the protonated BTM on the copper surface and this is followed by an overlayer of protonated BTM molecules.