engleski

EIS study of copper corrosion inhibition on RDE

Different corrosion inhibitors are used for copper protection in chloride media. The good inhibiting effect has been observed in case of compounds containing S, N or O atom such as imidazoles. This work aims at examining the inhibiting efficiency of two imidazole based compounds 4-methyl-1-(p-tolyl) imidazole (TMI) and 4-methyl-1- phenyl imidazole (PMI) as copper corrosion inhibitors in 0.5 M NaCl. Investigations were performed on rotating disc electrode (RDE) in order to evaluate the influence of the flow of electrolyte on inhibiting property of studied compounds because it is known that many corrosion inhibitors lose their inhibiting efficiency under flow conditions. Studies are performed at stationary electrode and at 1000 rpm. Electrochemical impedance spectroscopy measurements are conducted every hour during 1 day such that corrosion and corrosion inhibition may be followed in time. Studies performed on rotating disc electrode in 0.5 M NaCl indicate that the copper corrosion and its inhibition are influenced by mass transport. Although the presence of diffusion impedance is not clearly observed in EIS spectra, rotation of the electrode increases the dissolution of the corrosion products (CuCl). This reflects in a higher corrosion rate in the presence of rotation in both uninhibited and inhibited chloride solutions. It was shown that the examined imidazoles are efficient corrosion inhibitors. On the surface of copper two layers are formed, the inner oxide layer with adsorption of inhibitor and the outer layer composed of CuCl. The rotation of disk electrode hinders considerably the formation of this salt layer. The addition of TMI eliminates almost completely the formation of corrosion products ; because the rate of copper dissolution is so slow that almost all cuprous ions are leaving to the solution. The situation is very different in the presence of PMI. This compound forms a well structured fibrous complex. This complex is however porous and exhibit almost no barrier property. From these observations it is concluded that both studied inhibitors act mainly through hindering the dissolution kinetics rather than the formation of barrier film.

copper; corrosion inhibition; hydrodynamic effect

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