The aim of metal treatment process is to preserve the life of the weapon. Both iron and steel parts are vulnerable to corrosion and rusting and it is imperative to prevent these as much as possible. It is also a good idea to harden the metal parts in order to give them longer life and prevent deformation.
A second reason for metal treatment is to reduce the glare of the gun barrel, so that the user doesn't get blinded by the glare when aiming the weapon.
A third reason is merely to improve the cosmetics of the weapon. For instance, a browned barrel has a pleasing reddish-brown finish compared to an untreated barrel.
There have been several treatments developed throughout history: Case Hardening, Browning, Bluing, Parkerizing, Chrome plating, Tenifer etc. The metal treatment techniques that we will study in subsequent posts will deal with how these techniques were developed.