Pitting corrosion of copper in sulphate solutions: inhibitive effect of different triazole derivative inhibitors

The inhibitive effect of 3-amino 1,2,4-triazole (ATA) on the pitting corros ion of copper induced by sulphate ions was compared to that obtained with b enzotriazole (BTAH) and 1-hydroxybenzotriazole (BTAOH) and to previous resu lts obtained in chloride media. It was concluded that the inhibitive action of these compounds towards pitting corrosion was dependent on the aggressi ve species. For BTAH and BTAOH, the inhibitive efficiency was greater towar ds pitting induced by sulphate than towards pitting induced by chloride whi ch was explained by referring to the surface area covered by the organic mo lecules and to the size of the aggressive species. For ATA, an opposite beh aviour was observed and was explained by quantum chemical calculations. Fir st, the binding energy between clusters of Cu+ ions and Cl- was much weaker than that between clusters of Cu+ ions and SO42-. Secondly, the adsorption of Cl- on ATA linked to copper ions was more favourable than its adsorptio n on copper oxide. Moreover, the sulphate ion had a larger adsorption energ y on copper ions than on ATA linked to copper ions.