ABSTRACT
Iron and steels are the most versatile, least expensive and most widely applied of the engineering metals. The iron-carbon system is the basis for the most prolific ferrous materials, carbon steels and cast irons. The structures of steels have been the subject of an immense amount of observation and experience, commensurate with their economic importance. Rusting of bare iron and steel surfaces is generally slower in outside air than in water but is much more variable, ranging from near zero to over 0.1 mm per year and it is less predictable. The oxidation of iron at oxygen pressures near atmospheric pressure is worthy of study both because it is technically important and because it is complex and exemplifies many of the principles which underlie the oxidation of metals in general. The oxidation behaviour can be described within three mutually consistent contexts: crystallographic and defect structures of the oxides, phase equilibria for the iron-oxygen system, and Wagner's theory of oxidation mechanisms.
