In this work, the surface properties of Mg–Al–Zn (AZ91D) alloy such as surface morphology, hardness and electrochemical corrosion were studied after copper ions (Cu +) irradiation at different energies (0.8, 1.5, 2.5 and 3.5 MeV) while keeping the ion dose constant at 5 × 1 0 1 4 ions/cm2. The morphological features of irradiated samples showed defects composed of ejected material from the alloy surface that became more significant at 3.5 MeV. The Vickers hardness was increased with increase of the Cu + energy. The electrochemical testing of the samples was conducted in a Ringer Lactate solution. The potentiodynamic polarization results revealed anomalous changes in the corrosion rate of the Mg alloy with increase of the Cu + energy. The corrosion rate was considerably decreased with increase of the Cu + energy to 3.5 MeV. These changes were associated with the surface defects and passive film formation on the alloy surface. [ABSTRACT FROM AUTHOR]