The potentiostatic current oscillations at Fe-0.5 mol dm-3 H2SO4 interfaces are studied by using a holographic microphotographic technique. During the periodic current oscillation, a thick film is observed to dissolve and form regularly at the iron-solution interface. This thick film, which is probably of Fe(OH)2, provides a local high pH region which assists the production of Fe3O4 and help them remain temporarily stable. On the other hand, the backward diffusion of H+ in bulk solution will cause Fe(OH)2 and Fe3O4 to dissolve in sequence, thus the iron electrode is reactivated. Holographic microphotography is a very useful tool in studying electrode processes at the electrode-electrolyte interface.