USING INDOLE TO INHIBIT COPPER CORROSION IN AERATED 0.5 M SULFURIC-ACID

Inhibition of copper corrosion In aerated 0.5 M sulfuric acid (H2SO4) solutions containing various concentrations of Indole was studied in t he temperature range from 25 degrees C to 55 degrees C using potentiod ynamic curve, weight-loss, and analytical methods. Indole shifted corr osion potentials toward more noble values (I.e., it had a stronger inf luence on the copper dissolution reaction than on the cathodic oxygen reduction). Indole probably affected the corrosion reaction mechanism through complexes with cuprous ions. At 25 degrees C, 35 degrees C, an d 45 degrees C, the adsorption behavior of indole followed Frumkin's i sotherm At 55 degrees C, it followed that of Langmuir. The standard fr ee energies of adsorption (Delta G degrees((ads)))were -21.6 kJ/mol, - 18.3 kJ/mol, -22.1 kJ/mol, and -27.9 kJ/mol, respectively.