In situ studies of imidazole and its derivatives as copper corrosion inhibitors - I. Activation energies and thermodynamics of adsorption

The objective of this work was to investigate the efficiency of imidazole a nd its derivatives 4-methylimidazole, 4-methyl-5-hydroxy-methylimidazole, 1 -phenyl-3-methylimidazole, and 1-(p-tolyl)-4-methylimidazole for corrosion inhibition of copper in 0.5 M hydrochloric acid. Corrosion inhibition was s tudied using potentiodynamic methods. These studies have shown that 1-(p-to lyl)-4-methylimidazole has the best inhibitory efficiency. Activation energ ies were obtained by measuring the temperature dependence of the corrosion current. The activation energies in the presence of the various inhibitors are low (3-5 kJ/mol), with the best inhibitor showing the highest value. Th e adsorptive behavior of the imidazole derivatives on the copper electrode surface follows a Freundlich-type pe isotherm. The standard free energies o f adsorption are also low (14-16 kJ/mol), indicating that imidazole and its derivatives physisorb on the copper surface. Possible mechanisms of corros ion inhibition for these molecules are discussed. (C) 2000 The Electrochemi cal Society. S0013-4651(99)06-078-4. All rights reserved.