SPECTROCHEMICAL CHARACTERIZATION OF BENZOTRIAZOLE ON COPPER

The spectroelectrochemical behavior of Cu in 1 M sodium acetate soluti on, pH 5.8, alone and in the presence of benzotriazole (BTA) was inves tigated by cyclic voltammetry, impedance spectroscopy, and Raman spect roscopy. Impedance spectra are characterized by two time constants rel ating to charge transfer and transport of copper ions through the surf ace film, the latter being the rate-determining factor. The finite dif fusion impedance is analyzed using a diffusion factor (B), which is a function of the diffusion layer thickness (d) and the diffusion coeffi cient D-f for Cu+ species. The analysis suggests that changes in the f ilm thickness can be monitored in situ by impedance spectroscopy. The values of D-f and concentration of Cu+ species (c(f)) in the film form ed in the presence of 1 M BTA were estimated to be of the order 10(-14 ) cm(2) s(-1) and 10(-6) mol cm(-3), respectively. The results indicat e that the film formed at higher inhibitor concentration and longer im mersion time behaves almost like an ideal capacitor. Its thickness (up to 20 nm) and protection against corrosion increase by increasing the BTA concentration and immersion time. The results obtained by Raman s pectroscopy confirm the model for the complex Cu(I)BTA in which overla p of Cu sp-hybrid atomic orbitals with the N-hybridized lone-pair atom ic orbital occurs.