The variation in the rate of fluorine loss from electron‐bombarded Na3AlF6films with time, beam‐current density, and temperature is reported. The loss is shown to be due to the emission of F atoms; the observation of F2emission is shown to be an experimental artifact. A kinetic model is proposed which involves movement of fluorine into the bombarded area and which provides a good quantitative fit to a range of experimental data. The value for the cross section for dissociation of Na3AlF6under bombardment with 500‐eV electrons is found to be (1.35±0.4)×10−16cm2.