https://doi.org/10.15255/KUI.2005.014
Published: Kem. Ind. 55 (6) (2006) 253–259
Paper reference number: KUI-14/2005
Paper type: Original scientific paper
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Influence of Imidazole Derivatives on Copper Corrosion

H. Otmačić Ćurković

Abstract

Inhibiting efficiency of non-toxic imidazole derivatives (presented on Figure 1), as copper corrosion inhibitors in w = 3 % NaCl solution, was studied in the present work. Electrochemical investigations performed by potentiodynamic polarization measurements have shown that all studied compounds decrease the rate of copper corrosion while their inhibiting efficiency increases with molecular mass (Table 1). Except the molecular mass, the nature of the supstituent significantly influences the inhibiting property. Compounds containing alkyl supstituent show lower inhibiting efficiency than aryl containing imidazoles, but their efficiency is temperature independent while the efficiencies of aryl supstitued imidazoles slightly decrease with the increase of temperature (Fig. 3). Furthermore, alkyl imidazoles influence more on cathodic corrosion reaction, while aryl imidazoles have more influence on anodic corrosion reaction. Additional electrochemical (EQCM and EIS) and spectroscopic investigations have shown that, even between the two most efficient corrosion inhibitors, 1-phenyl-4-methylimidazole and 1-(p-tolyl)-4-methylimidazole, exist important differences in the mechanism of retardation of the corrosion process. The inhibitor that contains the tolyl substituent decreases the corrosion rate of copper due to the formation of thin layer of adsorbate, while in the case of 1-phenyl-4-methylimidazole, formation of thick layer can be followed with time (Fig. 4). From EIS (Electrochemical Impedance Spectroscopy) studies, it was observed that these inhibitors significantly increase absolute impedance of copper which shows that they efficiently protect copper from corrosion. In the case of 1-phenyl-4-methylimidazole absolute impedance increases in time (Fig. 5 and 6) which means that the protective layer is slowly forming on the metal surface. Studies performed in the presence of 1-(p-tolyl)-4-methylimidazole showed that already after short immersion time (Fig. 5) very protective surface film is formed and it remains stable in time (Fig. 6.) Investigations performed by SEM and AFM measurements confirm that 1-phenyl-4-methylimidazole forms three-dimensional protective surface layer while in the presence of 1-(p-tolyl)-4- -methylimidazole copper surface is protected by a thin inhibitor film.

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Keywords

corrosion inhibitors, chloride medium, electrochemical impedance spectroscopy, quartz crystal microbalance