Electron beam currents of a few nanoamps, currently used in nanometer scale scanning Auger microscopy scanning electron microscopy, promote oxidation of polycrystalline Ni3Al to a degree that depends on the size of the beam and subsequently on the electron flux cp,. In fact, the oxidation of Ni3Al at room temperature follows a model based on the premise that the electron beam creates additional nucleation sites around which oxide growth occurs. With increasing beam size the oxidation process becomes slower and O chemisorption plays a significant role. As a result the Ni-oxide depth decreases drastically with an increasing spot size (or equivalently decreasing electron flux). It offers an alternative way to monitor the NiO thickness in the nanometer range.