Electrochemical Studies of Cu-Al Alloys in Sulphate Solutions with Different pH

R.D. Noce, C.S. Fugivara, N. Barelli, A.V. Benedetti*

Instituto de Química da Universidade Estadual Paulista, UNESP. Departamento de Físico-Química, CP. 355, 14801-970 Araraquara, SP, Brasil. E-mail: benedetti@iq.unesp.br

Received 10 September 2002; accepted in revised form 29 January 2003

Abstract

The electrochemical behavior of Cu-(0.5-13 wt.%)Al alloys in K₂SO₄ 0.5 mol dm^-3 (m = 1.5 M, pH 2-5) was studied using open-circuit potential (E_oc) measurements and polarization curves, in order to know the conditions of copper oxides formation, influence of Al concentration and solution pH on the electrode processes. The open-circuit potential measurements with time indicated that the E_oc decreases with the Al content, due to the lower Al potential compared to Cu. The electrode potentials decrease ca. 20 mV per unity of solution pH as increase pH of the solution. The polarization curves showed changes with the increase of Al concentration. For alloys with up to 3 wt.%Al the obtained Tafel anodic coefficient was 40 mV/decade for low potentials region (E < -320 mV) and 130 mV/decade for the other region (-320 < E/mV < -250), indicating that up to this concentration there is no considerable change in the  electrochemical behavior of the alloys, when compared to pure Cu. For alloys with an Al content from 8 to 13 wt.% the Tafel anodic coefficient was 60 mV/decade. No influence of the solution pH on the Tafel anodic coefficient was observed.

Keywords: Cu-Al alloys, electrochemical oxidation.

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* Corresponding author. E-mail address: benedeti@iq.unesp.br.

Communication presented at XV Ibero-American Meeting of Electrochemistry.