Surface composition of machined leaded brass

ESCA and RBS were used to obtain quantitative information on the thickness and nature of the surface layers formed on machined brasses containing 1-3% lead. The results show that the brass surface is strongly enriched in lead. The amount of this element accumulated on the surface increases with increasing bulk concentration. Lead appears to be present as islands partially covering the brass surface and having variable thicknesses up to several hundred A. The outermost layer of the islands is mainly a Pb hydroxycarbonate, under which PbO and Pb metal can be detected. Between the islands, the brass surface is covered by a layer of zinc oxide covering the Cu-Zn metallic phase. The accumulation of Pb at the surface is attributable to a smearing effect caused by the machining tool