Effect of adsorption of some azoles on copper passivation in alkaline medium

We have studied the adsorption properties and the effect of some azoles such as benzotriazole (BTA), mercaptobenzothiazole (MBT), benzimidazole (BIMD), mercaptobenzimidazole (MBIMD), imidazole (IMD) and tetrazole on the growth of oxide film on copper in 0.1 M NaOH. Cyclic voltammetry and electrochemical impedance spectroscopy are used to characterise the passivation process. The relative inhibition efficiencies of the azoles in controlling the oxide film formation is found to be in the order MBT > BIMD ≈ MBIMD > BTA ≈ IMD. We find that the azoles follow the Langmuir adsorption isotherm. Study of coverage by the measurement of capacitance obtained from the imaginary component of impedance (Z^′′) as a function of time indicates that in about 800 s more than 95% of the coverage is complete in all the cases of inhibitor adsorption.