A STUDY OF COPPER ELECTRODE BEHAVIOR IN ALKALINE-SOLUTIONS CONTAINING BENZOTRIAZOLE-TYPE INHIBITORS BY THE PHOTOCURRENT RESPONSE METHOD AND INTENSITY-MODULATED PHOTOCURRENT SPECTROSCOPY

The electrochemical behavior of copper electrodes in alkaline solutions containing benzotriazole, 6-tolytriazole and 1-(2,3-dicarboxypropyl)-benzotriazole was studied by the photocurrent response method and the intensity modulated photocurrent spectroscopy. The photocurrent observed from a Cu electrode in 0.1 M NaOH solution where the electrode surface was covered with Cu2O was the result of the recombination of the photoexcited electrons through the photoreduction of the Cu+ ions, which was then followed by a dark oxidation. In the case where both Cu2O and CuO were present on the electrode surface, the photocurrent was attributed to the photoreduction of CuO as well as the recombination process mentioned above. In solutions containing a corrosion inhibitor, the formation of a thin Cu2O film strongly bonded to the upper layer of the adsorbed inhibitor occurred at potentials up to 0.5 V more negative than that in the absence of an inhibitor. These Cu2O underlayers were probably intrinsic semiconductors. It was observed that the efficiency of an inhibitor on the copper corrosion correlated with its ability in stabilizing the Cu2O underlayer as well as its influence on the photocurrent response.