Cyclic voltammetric behaviour of a brass in alkaline media

The electrochemical behaviour of alpha brasses was studied hr NaOH solutions using the cyclic voltammetric technique to establish the effect of such variables us alloy composition, reversal anodic potential scan rate, NaOH concentration, and temperature. Compounds that formed on the surface during the anodic sweep there analysed using X-ray diffraction analysis (XRD). The data show that the voltammetric behaviour of alpha brass consists of two potential regions. The first or subcritical potential region was indicated by two anodic peaks designated A(1) and A(2). 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 A(3). A(4), and A(5), inhere 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 allot 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. (C) 2001 IoM Communications Ltd.