SPECTROELECTROCHEMICAL STUDY OF PASSIVE FILMS FORMED ON BRASS ELECTRODES IN 0.5 M H2SO4 AQUEOUS-SOLUTIONS CONTAINING BENZOTRIAZOLE (BTAH)

The formation of passive films on copper, 85/15 and 67/33 brasses has been investigated by potentiostatic and potentiodynamic polarization techniques using rotating disk electrodes (RDEs) in sulphuric acid media containing benzotriazole (BTAH), in aerated and deaerated solutions. The adsorbed passive film obeys the Langmuir isotherm and the equilibrium constant for its adsorption increases with increasing copper content of the metal surfaces investigated. The in situ Raman spectra of the 85/15 and 67/33 brasses in 0.5 M H2SO4 solutions containing BTAH are also presented. By comparison of the in situ Raman spectra with the Raman spectra of [Cu(I)BTA]n and [Zn2BTA4]n polymeric complexes, the protective film has been characterized as being composed of multilayers of the [Cu(I)BTA]n complex. The time and potential dependence of the in situ Raman spectra show that the spectra from the surface species are not surface enhanced. © 1990.