The worn surfaces of selected Cu-Al alloys, resulting from sliding contact with a sapphire right cylinder, along with unworn surfaces and wear debris, were characterized using an appropriate combination of scanning electron microscopy (SEM), optical stereomicroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). XPS, angle-resolved XPS (ARXPS) and ion sputter profiling techniques were employed to characterize surface compositional changes occurring in the unworn and worn surfaces as a function of increasing aluminum content. The transfer of Cu-Al alloy to the sapphire counterface (adhesional wear of the Al-bronze) increased with increasing aluminum content, which corresponded to increased wear and damage to the alloy surfaces. XPS and SEM analyses of pure copper and a Cu-1 weight percent (w/o) Al alloy showed the worn surfaces to consist of a smooth and continuous Cu2O layer. ARXPS analysis of as-polished and worn surfaces of Cu-4 w/o Al and Cu-6 w/o Al alloys showed significant surface enrichment by aluminum. The preferential formation of Al2O3 on the surface decreases the mechanical stability and adherence of the surface oxide layer to the Al-bronze, Disruption of the Al2O3 oxide layer combined with an increase in surface energy (increased aluminum content) greatly increases the probability of forming an interfacial bond at the sapphire-Al-bronze interface which is stronger in shear than the cohesive strength of the alloy. When these conditions prevail, transfer of Al-bronze to the sapphire occurs and adhesional wear and galling are observed.