IN-SITU CONTACT ELECTRICAL-RESISTANCE TECHNIQUE FOR INVESTIGATING CORROSION-INHIBITOR ADSORPTION ON COPPER ELECTRODES

Traditional electrochemical tests and the contact electrical resistanc e technique (CER) were used to investigate the effect on corrosion of pure copper (99.999 wt%) of adding benzotriazole (BTA) and 1-hydroxybe nzotriazole (1-OH-BTA) to acidic solutions (sulfuric acid [H2SO4], pH = 1.7, and sodium sulfate [Na2SO4] until total sulfate [SO42-] concent ration = 0.1 M). This technique permitted growth of oxide and/or salt films as well as adsorption of the organic inhibitors on the copper su rface to be evaluated, Formation of copper oxide ([Cu2O](2)), sulfate (CuSO4 . 5H(2)O), thiocyanate (CuSCN), and halogenyde (CuI, CuBr, and CuCl) films on copper electrodes was followed in situ in sulfate solut ions at various pH values under low overpotentials. Effects of pH, sol ution anion content, and/or the amount of BTA or 1-OH-BTA on electrica l 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 similar to 90% compa red to those of 1-OH-BTA, which reached a maximum of similar to 76% in 2 x 10(-3) M solutions. It was possible to distinguish between maximu m R of the surface film, found in solutions containing BTA, associated with the adsorption of neutral inhibitor molecules, and the sharp ris e in R attributable to [Cu(BTA)](n) complex formation.