X-ray photoelectron spectroscopy (XPS) and X-ray Auger electron spectroscopy (XAES) were used to characterise changes in the surface chemistry of different copper alloys (admiralty brass, Al brass and 90Cu-10Ni alloy) as a result of their interaction with ultra-pure water at 95C for periods of up to 200 hours. All alloys were treated at pH 8-11.5 using oxygen-containing water (oxidising environment) and oxygen free water (reducing environment). This allowed us to determine the role of the dissolved oxygen in changes of the chemistry of the resulting surface products. The surface composition of representative samples before and after treatment was determined by XPS and XAES using the ESCALAB 2 and the SigmaProbe electron spectrometer (VG Scientific, UK) with monochromatised Al radiation. Experimental results for admiralty brass demonstrated that under reducing conditions the protective surface layer is cuprous oxide while under oxidising conditions the surface oxide contains increasing amounts of cupric oxide (CuO). When a reducing condition is changed to an oxidising condition at an operating temperature of 95C with pH 9 - the surface layer undergoes a conversion from cuprous to cupric oxide. After exposure of admiralty brass at pH 10.5 the surface is mainly composed of zinc oxide and no cupric oxide was present on the surface after its exposure to an oxidising environment at pH 11.5. The role of the alloy composition to chemistry and stability of resulting surface products is discussed and the marked effect of the addition of carbon dioxide on the composition of surface layers formed in oxidising conditions is demonstrated.