INVESTIGADORES
YOHAI DEL CERRO lucia
congresos y reuniones científicas
Título:
Characterization of copper and brass surfaces in chlorinated tap water using phosphate ions as green corrosion inhibitor
Autor/es:
L. YOHAI; W. SCHREINER; M. VÁZQUEZ; M.B. VALCARCE
Lugar:
Florianopolis
Reunión:
Simposio; 10th International Symposium on the Passivation of Metals and Semi-Conductors and the Properties of Thin Oxide Layers; 2011
Resumen:
In previous work it has been demonstrated that the corrosion behaviour of copper and brass improves in the presence of phosphate ions, particularly when they are in contact with a moderately hard, highly carbonated and chloride-rich drinking water. A decrease in the copper cuprosolvency together with an increment in the pitting resistance, have been related to changes in the passive films on both materials. When PO43- is added as corrosion inhibitor, the film, becomes thinner, denser and more compact, and also changes its composition 1, 2. In addition, the efficency of this inhibitor has been evaluated in the presence of NaOCl, the most commonly used biocide in drinking water 3. When the inhibitor is added to ATW + NaClO, weight-loss tests showed that generalized dissolution is inhibited on copper and brass. Brass presented pitting in ATW and dezincification in ATW + NaClO, but the presence of phosphate ions was able to inhibit both types of localized attack. This investigation focuses on the influence of zinc as alloying element on the corrosion resistance of brass. Therefore, a comparative study of the surface oxide films naturally formed on copper and brass in contact with drinkable water containing phosphate ions and NaOCl is presented.      All the experiments were carried out using artificial tap water (ATW) pH 7.6. The inhibitor dosage tested is 10 mg L-1 as P, and the NaOCl dosage used is 5 mg L-1 as Cl2. The surface films are grown on copper and brass for 2 and 192 hs at the corrosion potential. Potentiodynamic reduction curves, ex-situ Raman spectroscopy and X-ray Photo-electron spectroscopy are used to evaluate the change in the passive layers. When copper is in contact with ATW the main component of the surface film is Cu2O. In the presence of phosphate as inhibitor, a more compact and thinner layer is developed. This layer is formed by a mixture of Cu2O, CuO and Cu(OH)2 4. However, in the presence of NaOCl the participation of (Cu)3PO4 is evident. In turn, the main components of the surface layer formed on brass are Cu2O and Zn oxo-hydroxides. When the inhibitor is incorporated to the water, the surface layer becomes thinner and more compact, with Cu2O and Zn3(PO)4 as the main components 4. When NaOCl is present the participation of Cu(II) compounds is not so important and the passive film is principally composed by Zn3(PO)4. This suggests that the presence of zinc as an alloying elements inhibits the participation of Cu(II) ions in the oxide film, which could be related to the differences in the pitting susceptibility 3.      References 1 M. B. Valcarce and M. Vázquez, Corrosion Science, Vol.52 (2010), p.1413–1420. 2 L. Yohai, M. Vázquez and M. B. Valcarce, Corrosion Science, Vol. 53 (2011), p.1130–1136. 3 L. Yohai, M. B. Valcarce and M. Vázquez, 61st Annual meeting of the international society of electrochemistry, 2010. 4 L. Yohai, R. Procaccini, W. Schreiner, M. Vázquez and M. B. Valcarce, 61st Annual meeting of the international society of electrochemistry, 2010.