A new mechanism of high temperature oxidation of iron is proposed. Diffusion of lattice vacancies in the iron is shown to influence the type of oxide that forms. It was found that with thin specimens an adherent film grew on one side and a loose film on the other. The adherent film followed the parabolic law. The loose film grew in a pseudo-linear manner. The formation of these two types of films is shown to be necessary from consideration of diffusion of iron through the metal and oxide lattices. Applying the same principles to large specimens it is shown that a different kind of oxide layer forms which was observed by Pfeil.
Photographs of magnetite slowly cooled from a high temperature indicate that a plate-like precipitate of Fe2O3 forms on the [111] planes of the magnetite.
A brief study was made of blistering. It is demonstrated that superficial blisters form on heating in air and photographs show the later positions of the blisters as the oxide layers grow thicker.
