Inhibiting Action of Benzotriazole on Copper Corrosion in Deaerated Sulfuric Acid Containing Ferric Ions by the Rotating Disc Electrode, Fluorescence, and Raman Spectroscopies

The rate of copper corrosion by ferric ions (~7 mM) in 0.5 M deaerated sulfuric acid in the presence and absence of benzotriazole (BTAH) has been studied. The rotating disk electrode (RDE) has been used in weight loss experiments. In the range of BTAH concentrations between 0 and 3.0 × 10⁻⁴ M, the Levich equation is obeyed; i.e., the process is still controlled by transport of ferric ions to the electrode surface. Total inhibition of the corrosion process is observed when the BTAH concentration equals 5.0 × 10⁻³ M. The protective film follows a Langmuir adsorption isotherm, with an adsorption constant of 8.8 × 10³ M⁻¹. The chemical nature of the passivating film formed on the copper surface in this medium has been studied by in situ and ex situ fluorescence and Raman spectroscopies and the surface film characterized as a polymeric [Cu(I)BTA] complex.