The application of 1-hydroxyimidazole-3-N-oxides as aluminium corrosion inhibitors in alkaline solutions

Abstract 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 Na 2 CO 3 (pH 12) aqueous solutions was investigated on the basis of the polarization log 1 = 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.