Steel is actually a kind of iron which contains carbon.

Because iron is a pure metal, it is very soft and usually cannot be used directly as engineering materials. And the way to make it harder is to add carbon to turn iron into steel.

There are many different types of steel, and different elements can be added to give steel different properties.

Most steels contain essentially manganese, phosphorus, sulfur, silicon, oxygen, nitrogen, and trace amounts of aluminum. The hardness, ductility, strength and other properties of steel can be affected by the addition of nickel, chromium, manganese, titanium, molybdenum, boron, niobium and other metals.

The addition of more than 13% chromium can improve the corrosion resistance of stainless steel. Another way to increase the corrosion resistance of stainless steel is to plating the metal into zinc steel (usually carbon steel) by electroplating or hot dipping the metal into zinc.