The depletion of Li beneath the surface of an AlLi sheet as a consequence of surface oxidation is investigated by Auger electron spectroscopy. By the improved spatial resolution compared to other sampling methods it is shown that the local oxidation rate varies over a wide range on a 10 μm scale. The local oxidation rate gives rise to a local Li depletion combined with the formation of pores in the underlying subsurface region; these pores have a strong influence on the diffusivities perpendicular to the surface. An average of the strongly varying Li concentration profiles resembles, however, the typical diffusion-like depletion curves which have been reported in previous investigations and can be described by a simple solution of a one dimensional diffusion equation. The results are compared with microhardness measurements; it turns out that microhardness values can give a qualitative estimate of the Li depletion as long as no high density of large pores occur in a band beneath the surface.