The migration of Fe in pure Al was studied by using a tracer sectioning technique. The penetration plots were fitted by a solution to the diffusion equation for the case where the surface flux was controlled by a surface barrier. This characterized the dissolution of tracer atoms from the intermetallic phases formed in the near-surface layer and was represented by an energy which was higher than the diffusion activation energy in the bulk. The diffusivity could be described by:

D (cm2/s) = 5.3 x 101 exp[-1.90(eV)/kT]

D.L.Beke, I.Gödény, I.A.Szabo, G.Erdélyi, F.J.Kedves: Philosophical Magazine A, 1987, 55[4], 425-43