Black oxidation creates a fine black rust on the surface of iron-derived parts, preventing the progression of rust. It’s kind of like sealing parts with good looking smooth black rust. It is widely used in sensitive parts as painting very sensitive parts will disrupt their dimensions. Its durability is high. It is also known as black phosphate, blackening chemical, gun paint in the market. It is used in black colored pieces that cannot be hung on the hanger. At the end of the process, a matte smooth black coating is obtained. The initial investment cost is low. It is difficult to apply because it works at high temperatures. There are also cold workers, but they are not efficient.