Ultrafine powders of different metals (Al, Ag and Fe) have been prepared by the inert gas evaporation method. In all cases the samples have been passivated by pure oxygen and air exposure before compaction of the material into 13 mm discs. Due to passivation with oxygen the individual grains are covered by a passivation layer that contains oxygenated phases. Depending on the metal, the characteristics of the oxide passivation layer leads to different properties of the consolidated material. Characterisation of the samples has been carried out by transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). For aluminium, a dense and compact oxide passivation layer prevents the material from grain growth during heating to temperatures above the melting point of the metal. Silver, as noble metal, does not form a passivation layer, so that a total coalescence of the nanometric silver grains occurs after heating in an argon atmosphere. An intermediate situation is observed in the case of Fe where grain growth is observed upon heating. Finally, we have found a stabilization of metastable γ-Al 2 O 3 and γ-Fe 2 O 3 (and/or Fe 3 O 4 ) phases in the passivation layers of Al and Fe, respectively. The formation of these γ-phases has been attributed to the nanometric character of the particles.