Stainless steel is the generic name for a number of different steels used primarily for their resistance to corrosion. Although other elements, particularly nickel and molybdenum, are added to improve corrosion resistance, chromium is always the deciding factor. The vast majority of steel produced in the world is carbon and alloy steel, with the more expensive stainless steels representing a small, but valuable niche market. Only metals such as gold and platinum are found naturally in a pure form normal metals only exist in nature combined with other elements. Corrosion is therefore a natural phenomena, as nature seeks to combine together elements which man has produced in a pure form for his own use.
Iron occurs naturally as iron ore.
Trains blown up in the Arabian desert in the First World War are still almost intact because of the dry rainless conditions. Iron ships sunk at very great depths rust at a very slow rate because of the low oxygen content of the sea water . The same ships wrecked on the beach, covered at high tide and exposed at low tide, would rust very rapidly. Steel did not begin to be produced in large quantities until the nineteenth century. Carbon steel can be defined as an alloy of a small content of carbon combined with well refined iron.