Electrochemical investigations of corrosion inhibition of Cu-Ni (90/10) alloy in sea water and sulphide-polluted sea water by 1,2,3-benzotriazole

摘要

The inhibiting effect of 1,2,3-benzotriazole (BTAH) against corrosion of Cu-Ni (90/10) alloy in sea water and sea water polluted with sulfide was studied by electrochemical impedance studies (EIS), potentiodynamic polarization studies and cyclic voltammetric (CV) studies. EIS studies have been carried out in the absence and presence of BTAH at different concentrations, different immersion periods and at different temperatures at the open circuit potential (OCP) in the frequency range from 60 kHz to 10 mHz. Both the Nyquist and Bode plots are interpreted. Appropriate equivalent circuit model is used to calculate the impedance parameters. In this model two different impedances are introduced, one to account for charge transfer across the film / solution interface and the second one to account for mass transfer and charge transfer at the metal / film interface. In the presence of BTAH, both the charge transfer resistance of the double layer and the film resistance are found to increase. The 'n' values corresponding to both the constant phase element of double layer and of the film are nearly equal to 1, which indicate that the BTAH film formed on the alloy surface acts as an ideal capacitor. Potentiodynamic polarization studies inferred that BTAH functions as a mixed inhibitor. The two characteristic anodic peaks that appeared in the polarization curve in sea water without inhibitor are practically absent in the presence of inhibitor. In the case of cyclic voltammograms, in the absence of inhibitor also two anodic peaks are observed, the first one being due to Cu→Cu~+ and the second one, due to Cu~+→Cu~(2+). Two cathodic peaks are also observed for the corresponding reduction reactions. Both the anodic and cathodic peaks are absent in the presence of BTAH. Cyclic voltammeric studies infer the stability of the protective film even at anodic potentials of 550 mV vs. Ag/AgCI. All these electrochemical techniques confirm that BTAH functions as an excellent inhibitor for Cu-Ni (90/10) alloy in sea water as well as sulfide-polluted sea water.