Black Oxide, sometimes called blackening, is the act of converting the top layer of a ferrous material with a chemical treatment. Treating fasteners with a black oxide coating not only adds a nice clean black look but can also add a mild layer of corrosion and abrasion resistance. To achieve the maximum in corrosion resistance, black oxide can either be waxed or oiled to add an extra layer of protection. The wax coating may dull the color of the treatment but provides the best resistance. 

The black oxide coating has the followed avantages:

Dimensional Stability - Black oxide's success is due to its ability to give cosmetic appeal without affecting dimensional properties.

Versatility - This process can be applied to many diverse metals including: carbon, alloy and stainless steels, copper, brass, bronze, die cast zinc, and cast iron.

Durability - The finish will not chip, craze, peel or rub off. The only way to remove the finish is by mechanical or chemical methods.

Protection - Oxidized surfaces have an excellent ability to absorb oils, waxes and lacquers. This enhances the appearance while protecting the treated metal or alloy.