X-ray photoelectron spectroscopy (ESCA) has been employed to study the oxidation of alpha-Cu-Zn alloys in the range, 65per thousand É46Cu É46 80per thousand. The process was conducted in air at room temperature, with moderate humidity, producing what has been previously labeled natural passivation. A combination of sputter etching and controlled growth studies have been employed to document the entire passivaiton process from inception to termination. The layering features have been described with emphasis on the resulting physical chemistry. The initial oxide layer formed, ZnO, seems to produce a depletion of Zn0 in the outer suface of the alloy. Cu0 appears trapped in this relatively thick (50-100 Å) ZnO layer. After the ZnO growth has extensively formed, an overlayer of copper oxides grow, first with Cu2O formation, then followed by a terminal Cu(II) layer, composed of CuO and Cu (OH)2. The latter layers are noticeably thinner than the corresponding oxide growth on pure Cu, perhaps due to the relatively small amount of Cu0 in th ZnO sublayer. A discussion of the Cabrera-Mott growth characteristics and their connection to the semiconductor status of the resulting oxides is included.