Europium-implanted aluminum shows an orange electroluminescence (EL) during anodization in a 0.1 M ammonium pentaborate solution. The emission spectra show that this EL can be ascribed to the 4f-electron transitions of Eu3+ in an Al2O3 films. The EL intensity shows a maximum at a forming voltage of 70 V. The EL mechanism can be related to anodization in an Eu-implanted aluminum surface layer.