engleski

THE INFLUENCE OF ANION AND pH VALUE OF THE SOLUTION ON THE EFFICIENCY OF AN IMIDAZOLE BASED CORROSION INHIBITOR

Azole compounds like triazoles, imidazoles and thiazoles, are known as efficient corrosion inhibitors for copper in different media. Their inhibiting action is influenced, among other parameters, by solutions pH value, because it determines corrosion mechanism, state of copper surface, as well as the state of inhibitor molecule (protonated, deprotonated). Therefore many inhibitors efficient in neutral medium show poor inhibition in acids. Previous investigations on corrosion protection of copper, have shown that 1-(p-tolyl)-4-methyl imidazole is a very efficient copper corrosion inhibitor in H2SO4 and NaCl solutions but its efficiency is much lower in HCl. The aim of this work is to study how the efficiency of this inhibitor changes from very acid to neutral media. Investigations are performed in sulphate and chloride solutions in order to study the influence of anion on the protective efficiency of 1-(p-tolyl)-4-methyl imidazole. The investigations are performed by electrochemical methods of potentiodynamic polarization, by electrochemical impedance spectroscopy and using electrochemical quartz crystal microbalance. The structure and the composition of the copper surface that was exposed to aggressive chloride and sulphate media with and without the presence of studied compound was examined by SEM/EDX. The results obtained by these investigations show differences in the inhibiting efficiency of 1-(p-tolyl)-4-methyl imidazole in the solutions with chloride and sulphate anion as well in the solutions of different pH. These observations can be explained considering the differences in corrosion mechanism occurring in studied media and due to the acid/base equilibrium of investigated corrosion inhibitor.

copper; pH; corrosion; corrosion inhibitor

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