The oxidation of a Cu50Zr50 shape memory alloy in air at room temperature was investigated. Both polished surfaces and surfaces subjected to Ar ion bombardment were exposed to air for different time intervals and studied by X-ray photoelectron spectroscopy. A ZrO2 layer with some metallic Cu was detected on the surface for oxidation times up to 1 h. Prolonged air exposure of polished samples led to oxidation of Cu and a decrease of the relative amount of ZrO2 on the surface. Preferential sputtering of the alloy by 3 keV Ar ions was also studied and surface enrichment of Zr was observed at steady-state conditions. (C) 1999 Elsevier Science B.V. All rights reserved.