AlN powders have been submitted to mechanical attrition in air. X-ray diffraction (XRD) and transmission electron microscopy (TEM) show that mechanical treatments are producing the fracture of primary particles and the incorporation of microstructural defects. At the same time, Bremsstrahlung excited Auger electron spectroscopy (AES) in conjunction with x-ray photoelectron spectroscopy (XPS) have allowed the surface characterization of the samples. Under mechanical attrition this surface oxidation increases after some minutes but then a steady-state situation is achieved with the formation of a nanometric passivation layer that contains Al(OH)3 and AlOOH species. This degradation layer prevents the material for further oxidation.