THE 1ST STAGES OF DEZINCIFICATION OF FRESHLY GENERATED BRASS SURFACES IN SULFURIC-ACID-SOLUTION

Kinetic data have been obtained which describe the early stages of dezincification of brasses from surfaces which have been freshly generated in situ in sulfuric acid solution. At potentials below the Cu/Cu(I) and Cu/Cu(II) equilibria pure copper shows anodic activity to a small extent, modeled in terms of the growth of a single monolayer of oxide. At similar potentials brasses show anodic activity enhanced over that of copper, both in rate and in extent. The excess reaction of brasses describes dezincification during the course of growth of the copper oxide monolayer. After completion of this first stage, dezincification proceeds into the second stage for which the oxidation charge density increases as t0.25, where t is time. The rate and extent of dezincification during these early stages depend strongly on the zinc content of the alloy, at least up to 65 weight percent Zn.