The Presence of Excess Oxygen in Burning Metallic Materials

Early work on burning of iron rods under conditions of the ASTM/NASA flammability test showed that there was excess oxygen, that is, above stoichiometric requirements for Fe2O3, present in the molten product formed during burning. Since that initial work, this phenomenon has been confirmed for burning under microgravity conditions and has been observed for a wide range of metals under various burning conditions at ambient pressures and under pressurized oxygen-enriched conditions. This paper reviews these experimental observations and discusses the possible thermodynamic analysis for the metals iron, cobalt, and nickel. The excess oxygen in the burning molten iron oxide is represented as combined to form a series of ferrite ions. For cobalt the excess oxygen is represented as a bridging species; that is, the cobalt oxide liquid is oxygenated. There is no definitive evidence for excess oxygen in nickel oxide.