THE ROLE OF NITROGEN AND SULFUR HETEROCYCLES IN CORROSION INHIBITION .1. INITIAL STEPS IN THE ADSORPTION OF BENZOTRIAZOLE AT COPPER(I) AND COPPER(II) OXIDES

The adsorption of benzotriazole (BTAH) on Cu2O and CuO surfaces from a variety of aqueous and nonaqueous solutions has been studied using X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and transmission UV measurements. At solution concentrations [BTAH] < 5 X 10(-3) M a chemisorbed layer is formed on both surfaces within 500 s. Two possible structural models are considered: (A) an adsorbed monolayer of pure BTAH and (B) a thicker mixed Cu/BTAH layer. AES depth profiling and angle-resolved XPS measurements are consistent only with model A. The coverage of this pure monolayer is established by comparison of Auger and transmission UV measurements. For chemisorbed BTAH on a Cu2O surface, the calibration between integrated intensity of the 278-nm band and the surface density is established as 2.7 x 10(14) molecules/cm2 is similar to integral A dlambda = 0.50. Finally a comparison of solution and adsorbed UV band structures and an increase in the apparent transition probability by a factor of 4 upon adsorption indicate that dissociation of BTAH into BTA- and H+ upon adsorption is likely.