Comparative study of inhibition effects of benzotriazole for metals in neutral solutions as observed with surface-enhanced Raman spectroscopy

Surface-enhanced Raman spectroscopy has been successfully extended to the study of corrosion inhibition of bare iron and nickel metals. The inhibition effects of benzotriazole (BTAH) for copper, iron, and nickel electrodes in 0.1 M KCl solution were investigated by using both polarization curves and in situ Raman techniques. The protective films formed on copper and iron surfaces, in the presence of BTAH, are characterized as [Cu(I)BTA](n) and [Fe-II(BTA)(2)](n), respectively. The formation of Fe-N coordinated bonds and the deprotonation of the triazole ring may occur while BTAH interacts with the iron surface. On the contrary, BTAH may interact with the nickel surface as neutral molecules in the whole potential range investigated resulting in a poor inhibition effect. The surface complex is characterized as [Ni-BTAH]. The potential dependence of the Raman spectra on copper and iron shows that the BTA(-) ion in the surface complex may rebind with H+ at more negative potentials and accordingly the inhibition efficiency of benzotriazole decreases.