Magnetite Scale Research Articles

A novel method of interface exposure

A method has been found of removing intact an oxide scale from the underlying metal, without recourse to chemical treatment; since the removal occurs by separation along a line of weakness, it often leads to exposure of interfaces that would not otherwise be accessible. The method consists of coating the oxidised specimen with a suitable material, in this case nickel, by sputter ion plating at an elevated temperature. The thickness of the nickel coating and the temperature of plating are chosen so that on cooling, the stored elastic energy in the nickel is greater than the fracture energy of the weakest region in the scale. When nickel is then removed from the edges of the specimen, the remaining nickel coating peels away from the metal taking the scale with it. In the case of Fe/Si alloys oxidised in CO 2, the line of weakness, as revealed by surface analysis by XPS, was either at the interface between the magnetite scale and the layer of accumulated oxidised silicon adjacent to the metal, or at the interface between the inner and outer oxides. The method may have general applications in the study of spalling.