THE APPLICATION OF 1-HYDROXYIMIDAZOLE-3-N-OXIDES AS ALUMINUM CORROSION-INHIBITORS IN ALKALINE-SOLUTIONS

The influence of the 1-hydroxyimidazole-3-N-oxide (HOI), 1-hydroxy-2-benzoyl-5-phenylimidazole-3-N-oxide (HOBFI) and 1-hydroxyimidazole-2,4,5-trimethyl-3-N-oxide (HOTMI) on aluminium corrosion in 0.01 M NaOH, (0.01 M NaOH + 3% NaCl) and 0.1 M Na2CO3 (pH 12) aqueous solutions was investigated on the basis of the polarization log I = f(E) curves, a.c. impedance measurements. and electrochemical noise experiments. The 3-N-oxides shift the corrosion potential of aluminium to more positive potentials (i.e. HOTMI shifts E(corr) about 900 mV) and decrease the corrosion current (i(corr)) by approximately two orders of magnitude. These results may be interpreted as the adsorption of inhibitors coupled with the redox reactions of the 3-N-oxides and the creation of a polymer layer on the aluminium surface.