Black Oxide Coating: What Is Black Oxide?

Black Oxide, often known as blackening, is the chemical process of turning the top layer of a ferrous substance. Fasteners treated with a black oxide coating not only have a great clean black appearance, but they also have a modest layer of corrosion and abrasion resistance. Black oxide can be waxed or oiled to offer an extra layer of protection for ultimate corrosion resistance. The wax coating dulls the treatment's color but gives the best resilience. Gun bluing is another name for the black oxide process.

When fasteners are immersed in black oxide bath materials (both warm and hot procedures), the harsh chemical components transform the top layer into magnetite. The most prevalent type of black oxide fastener is black oxide stainless steel nuts, bolts, and washers. Stainless steel is valued for its corrosion resistance, as well as the added benefits of the black oxide treatment.

Cylindrical-Roller-Black-Oxide

Materials That Can Get The Black Oxide Treatment

Stainless Steel
Copper
Copper Based Alloys
Zinc
Powdered Metals
Silver Solder

The Black Oxide Processes

Blackening can be achieved in a number of different ways. There are three main ways to do this. If you are interested in the specifics of each type check out this article from Wikipedia.

Hot Bath

The procedure of immersing fasteners in various chemicals to transform the surface material into magnetite. The fasteners are finished by being dipped into various tanks and occasionally immersed in water. When the dipping process is finished, the top layer of the fastener is porous and a layer of oil is applied. The oil permeates into the material, increasing its corrosion resistance against rust. This method produces a black oxide bath that meets the criteria of MIL-DTL-13924, AMS 2485, ASTM D769, and ISO 11408.

Cold Coating

At room temperature, the cold process imparts a chemical (copper selenium) on the fasteners. This procedure is more suitable for working in the home because it does not involve the application of many chemicals at high temperatures. It is considered weaker than the other forms of oxidization once applied until a layer of oil or wax is put to the surface.

Mid-Temperature Bath

Like the hot bath treatment process, but without the poisonous gases, and the surface is changed to magnetite at a considerably lower temperature. This procedure can also generate the same military standards as the hot bath variant.

Benefits Of Black Oxide Fasteners

Hot dip galvanizing considerably alters the size of the fasteners.
A less expensive alternative to conventional corrosion resistance procedures such as electroplating.
When a dazzling shine is not wanted, this is a pleasing look.
The technique is typically done in big volumes, making it faster and less expensive for smaller sizes.
By using an oil finish, the possibility of galling is reduced.
Finishing touches
Provides a coating of corrosion and abrasion protection.
If painting is required, paint adheres effectively to the black finish.