The role of benzotriazole in corrosion inhibition: formation of an oriented monolayer on Cu 2O

Abstract

Studies of the adsorption of benzotriazole (BTAH) on Cu 2O surfaces have been carried out up to saturation coverage using both experimental (transmission UV and Auger electron spectroscopy (AES)) and computational approaches. Correlation of the UV integrated band intensity for the adsorbed BTA − species with quantitative measurements of N/Cu ratios from AES shows the saturation coverage of chemisorbed BTA − to be Γ ML ≈ 6.3 × 10 14 cm −2. Calculations based on a molecular mechanics (MM2) minimization of the BTA − structure show a maximum surface density of 8.3 × 10 14 and 2.4 × 10 14 cm −2 for orientations in which the BTA − plane is perpendicular and parallel to the surface, respectively, thereby indicating that BTA − cannot be bound with the ring plane parallel to the surface under these conditions. Furthermore, the orientation is invariant with surface density, as demonstrated by coverage-dependent dichroic ratio measurements. Semi-empirical calculations of free BTA − and transmission linear dichroism measurements suggest that an orientation in which the ring plane is perpendicular to the surface with the C 2 axis canted away from the surface normal is the most reasonable proposal for the structure of the adsorbed layer.