The A12O3 layer on moten aluminium alloys can be damaged in some technological conditions. By capillarity the molten metal will rise to the surface through the broken place on the loyer and form a new A12O3 layer which is not compact and can be passed by molten metal too. This is a self-organic process by which a self growing A12O3-A1 composite with some thickness will be formed on the surface of the molten metal. The proportion of A12O3 in the material can be controlled from 20%-80% while the qualities especially the hardness and tensile strength, are all higher than thoses of the powder metallurgy materials.