Some aspects of copper corrosion in presence of benzotriazole and chloride ions

This paper deals with the investigation of electrochemical behaviour of copper in a sodium tetraborate (borax) solution in the presence and absence of chloride ions. The influence of benzotriazole (BTA) on the anodic behaviour of copper was also investigated. It was found that Cu₂O and CuO oxides were formed on copper and that peak current moved to the positive side with increased immersion time in a sodium tetraborate solution. After 1 h immersion of the copper electrode in a sodium tetraborate solution containing various chloride ion concentrations (0.001, 0.010, 0.050, and 0.100 mol/dm³ Cl⁻) the activation effect of those ions was found, whereas after 6 h immersion of copper in the above mentioned solutions, chloride ions were found to have not only activation but also passivation effect. The investigation of the effect of benzotriazole led to a conclusion that BTA has an inhibiting effect with increasing immersion times (15 min, 1 h, 4 h, and 48 h) as well as with increasing BTA concentrations (8.4 × 10⁻⁶, 8.4 × 10⁻⁵, 8.4 × 10⁻⁴, and 8.4 × 10⁻³ mol/dm³). In addition, at the lowest investigated BTA concentration (8.4 × 10⁻⁷ mol/dm³) an activation effect of this compound on copper dissolution was observed. Based on the Langmuir adsorption isotherm, the value of the standard free energy adsorption was found to be ΔG⁰ = −35.4 kJ/mol.