Chromium Steels

If an unalloyed steel is exposed to high temperatures it oxidizes fairly rapidly. This is due to the relatively high affinity of iron for oxygen; the oxide layer formed does not provide the underlying steel with sufficient protection against further oxidation. When chromium is added to the steel, however, the oxide layer adheres far better to the metal and at the same time its structure is such that progressive oxidation is to a large extent suppressed.