CONICET | Buscador de Institutos y Recursos Humanos

Copper is a widely used metal in industry and technology because of its excellent thermal and electrical properties, but it reacts easily in media containing oxygen. Inhibitors are usually employed to reduce copper instability, but most of them are highly toxic and environmental protection requirements demand green inhibitors. Cysteine (cys), an amino acid with a thiol group, soluble in aqueous media and of easy preparation, could fulfill this role. The objetive of this work is to research into the interaction of cys (10-2 M) with the surface of copper electrodes in buffer solutions of carbonate-bicarbonate, pH 8,9 and 0,09 M ionic strength. Electrochemical impedance spectroscopy (EIS), scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDS) techniques, and open circuit potential measurements (Eoc) were used. Tests were performed in solutions with and without the addition of cys to evaluate the copper surface behaviour. First, the previously polished electrodes were subjected to cathodic polarization in the fresh solution. Then, the Eoc evolution was recorded for 6 hours followed by EIS measurements. This procedure was repetead every 24 hs for 8 days without taking out the electrode from the cell. Finally SEM-EDS measurements were carried out. The results obtained would indicate that there is a metallic surface-cys interaction through the sulphur atom that would favor the reduction of cuprous oxide and would produce a complex between copper and organic molecule. As Cu immersion time in the cys solution increases, changes appear either in film thickness or in the formation of a multilayer. Protection decreases in prolonged immersion times due to changes in the film. SEM- EDS studies confirm cys permanence on copper and the increase of sulphur concentration on the surface with immersion time, associated to increase in film thickness or to the formation of a multilayer.