Electrochemical Impedance Spectroscopic Investigations of the Corrosion Behaviour of Brass Alloys in Aqueous Solutions

Abstract

Brass alloys are technologically important materials due to the wide range of their industrial applications. Extensive efforts have been directed to investigate the corrosion and stability of these alloys. The corrosion behaviour ofthese materials is always related to the study of the dezincification process or the selective dissolution of the active components of the alloy in the different media under different conditions. Due to the lack of systematic study of the electrochemical behaviour of these alloys in aqueous solutions at different pH, it was found essential to cover this area Electrochemical impedance spectroscopy (EIS) and polarization techniques, are powerful to investigate the electrochemical processes occuring at the electrode / electrolyte interface. The techniques enables mechanistic studies beside corrosion rate determination. In this work, the corrosion and passivation behaviours of three different brass alloys in aqueous solutions of various pH, covering the acidic, neutral and basic media were studied and a comparison with the corrosion behaviour of the pure elements under the same conditions made. EIS and polarization techniques beside open circuit potential measurements were used. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were employed to explain and to confirm the corrosion phenomena occuring at the alloy surface. Preliminary data have shown that the selective dissolution of Zn and Pb from the alloys under open circuit conditions occur in acidic and basic media more than in neutral solutions and the behaviour cannot be explained on the basis of pure pH effects.