Spectroelectrochemical studies of protective surface films against copper corrosion

The structure of the Cu/surface layer/electrolyte interfaces was studied by spectroelectrochemical methods in a slightly acidic aqueous solution containing benzotriazole (BTAH) and its derivative, dibenzotriazole-1-yl-methyloctylamine (DBTO) in a wide concentration range. Impedance measurements indicated a complex structure of the surface layer. A physical model describing corrosion inhibiting process on the copper surface was developed. The derived transfer function was discussed in terms of mass transport (the film limited diffusion of metal ions) and charge-transfer controlled corrosion steps. A correlation between the concentration of inhibitors and immersion time in relation to the inhibition efficiency and the surface layer thickness was established. Raman spectra of solid BTAH and DBTO and SERS spectra of the Cu foil treated in the solution containing BTAH and DBTO were measured and analysed. Both impedance and SERS spectra showed a multilayer structure of the surface film: Cu/Cu_2O/Cu(I)inhibitor. The ability of investigated compounds to act as corrosion inhibitors was discussed in view of structural information obtained from impedance and SERS spectra.