Tanning is the process of making leather, which does not easily decompose, from the skins of animals, which do. The materials which can tan leather are known as tannins. These can be produced naturally or synthetically.
The production of leather depends on the generation of complexes between the tanning agent and the skin collagen.
Chromium metal is widely used as a tanning agent worldwide. The process called chrome-tanning is accomplished in three steps: Pickling, Tanning and Basification.