How relevant is the adsorption bonding of imidazoles and triazoles for their corrosion inhibition of copper?

Imidazole, 1,2,4-triazole and their 1-methyl derivatives were evaluated as copper corrosion inhibitors in NaCl solution by corrosion experiments and their bonding to Cu(111) was characterised by DFT calculations. Deprotonated triazole adsorbs considerably stronger than 1-methyl-triazole, whereas deprotonated imidazole displays only slightly more exothermic aqueous-phase adsorption free energy than 1-methyl and neutral imidazole. This suggests that triazole should be a more efficient inhibitor than 1-methyl-triazole, whereas the efficiency of imidazole and 1-methyl-imidazole should be similar. The experimental measurements only partly support this inference, because 1-methyl-imidazole accelerates corrosion at higher concentrations.