Technical Note: Dezincification of Alpha-Brass in Crevices

An earlier paper showed that dezincification of α-brass could be monitored electrochemically by simulating the solution that would develop in an anodically polarized cavity and then carrying out a test in this solution at zero volts vs a copper reference electrode.¹  This research was partly based on an approach originally developed by Lucey.^2,3  Having carried out such tests, it is obvious how dealloying occurs in practice: oxygen reduction on relatively bare parts of the brass surface supports diffusion-controlled copper dissolution (as CuCl₂^–) under deposits or corrosion products that act as diffusion barriers. The solution on the corroding surface is equilibrated with copper in the alloy, and dezincification can start provided the diffusion-controlled partial anodic current density of Cu is much less than that achievable by zinc. The latter may vary with the chloride concentration, temperature, alloy zinc concentration, cold work, and especially the presence of...