Cyclic voltammetric behaviour of – brass in alkaline media

Abstract

The electrochemical behaviour of a brasses was studied in NaOH solutions using the cyclic voltammetric technique to establish the effect of such variables as alloy composition, reversal anodic potential, scan rate, NaOH concentration, and temperature. Compounds that formed on the surface during the anodic sweep were analysed using X-ray diffraction analysis (XRD). The data show that the voltammetric behaviour of – brass consists of two potential regions. The first or subcritical potential region was indicated by two anodic peaks designated A₁ and A₂. Within this potential region, selective dissolution of the less noble component, zinc, occurs (i.e. dezincification). The second potential region consists of three anodic peaks, designated A₃, A₄, and A₅, where the two components of the alloy, namely copper and zinc, dissolve simultaneously. Alloying zinc with copper resulted in a decrease in the dissolution of zinc from the alloy. This behaviour could be explained on the basis that the dissolution is limited by the non-steady state diffusion of zinc atoms from the bulk of the alloy to the alloy solution interface, which implies that the rate determining step of dezincification is the diffusion of zinc atoms. The process of preferential dissolution of zinc leads to the formation of a layer rich in copper and depleted in zinc on the electrode surface.