engleski

Influence of Iodide Ions on Copper Corrosion Inhibition by Azole Compounds

Different azole compounds efficiently protect copper from corrosion in many media [1-3]. Their inhibiting efficiency is highly influenced by the pH value of the electrolyte. In highly acidic solutions, the inhibiting efficiency of many organic inhibitors decreases due to the lower adsorption of protonated inhibitor molecules. Investigations conducted in sulfuric acid have shown that iodide ions can greatly enhance adsorption of protonated inhibitor molecules on the metal surface and therefore improve their inhibiting action in acid environment [3]. The aim of this work is to determine whether iodide ions can promote adsorption of azoles on copper in hydrochloric acid. The azole compounds studied are benzotriazole, 1-(p-tolyl)-4-methylimidazole and 1-phenyl-4-methylimidazole. Investigations were performed through electrochemical polarization measurements and electrochemical impedance spectroscopy. Our study has confirmed the synergism of investigated azoles and iodide ions. The presence of iodides greatly enhances the inhibition efficiency of benzotriazole, while the efficiency of imidazoles has been improved to a lesser extent. Although both the benzotriazole and two imidazole compounds studied are mixed-type inhibitors, in the presence of iodide ions, the benzotriazole behaves as a predominantly anodic inhibitor, while 1-(p-tolyl)-4-methylimidazole and 1-phenyl-4-methylimidazole behave as predominantly cathodic-type inhibitors. The difference in the corrosion inhibition mechanism is explained based on the difference in molecular structure of investigated azoles.

copper corrosion inhibition; synergistic effect; iodide

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