In-Situ Contact Electrical Resistance Technique for Investigating Corrosion Inhibitor Adsorption on Copper Electrodes Available to Purchase

Traditional electrochemical tests and the contact electrical resistance technique (CER) were used to investigate the effect on corrosion of pure copper (99.999 wt%) of adding benzotriazole (BTA) and 1-hydroxybenzotriazole (1-OH-BTA) to acidic solutions (sulfuric acid [H₂SO₄], pH = 1.7, and sodium sulfate [Na₂SO₄] until total sulfate [SO₄^2–] concentration = 0.1 M). This technique permitted growth of oxide and/or salt films as well as adsorption of the organic inhibitors on the copper surface to be evaluated. Formation of copper oxide ([Cu₂O]₂), sulfate (CuSO₄·5H₂O), thiocyanate (CuSCN), and halogenyde (CuI, CuBr, and CuCl) films on copper electrodes was followed in situ in sulfate solutions at various pH values under low overpotentials. Effects of pH, solution anion content, and/or the amount of BTA or 1-OH-BTA on electrical resistance (R) of the surface films formed on pure copper electrodes were treated. BTA acted as a more efficient corrosion inhibitor than 1-OH-BTA, reaching inhibition percentages (IP) of ~ 90% compared to those of 1-OH-BTA, which reached a maximum of ~ 76% in 2 x 10^–3 M solutions. It was possible to distinguish between maximum R of the surface film, found in solutions containing BTA, associated with the adsorption of neutral inhibitor molecules, and the sharp rise in R attributable to [Cu(BTA)]_n complex formation.