Surface-enhanced Raman scattering (SERS) of benzotriazole derivative corrosion inhibitor prepared in aqueous media

The surface structure and inhibiting properties of a benzotriazole (BTAH) d erivative, dibenzotriazole-1-yl-methyloctylamine (DBTO), on a copper surfac e in 1 M sodium acetate solution (pH 5.8) were investigated by cyclic volta mmetry, impedance spectroscopy and Raman spectroscopy. Raman spectra of pur e DBTO and BTAH, their complexes with Cu (I) ions and surface-enhanced Rama n scattering (SERS) spectra of DBTO and BTAH molecules on a copper surface were measured and analysed. Almost identical SERS spectra of DBTO and BTAH. on a copper surface, as well as very similar inhibiting properties and str ucture parameters of their surface films obtained by impedance measurements , pointed to identical chemical composition. It seems that, after having be en adsorbed on a copper surface, DBTO molecules lost their aliphatic chain and reacted with copper(I) ions to form a surface layer. Both Raman and imp edance spectra have shown a multilayer structure of the surface film: Cu/Cu 2O/Cu(I) inhibitor. The results of impedance measurements indicated that th e surface film was of a dielectric nature. Similarly to BTAH, its thickness and protection against corrosion increased with increasing inhibitor conce ntrations and/or ageing. At low inhibitor concentrations and shorter immers ion time, DBTO molecules were chemically adsorbed on the electrode surface. The adsorptive behaviour followed a Frumkin adsorption isotherm with free energy of adsorption Delta G = -19.5 kJ mol(-1). Copyright (C) 1999 John Wi ley & Sons, Ltd.