What Is Black Oxide Coating and What Does It Do?

Black Oxide Coating

The process of black oxide coating is when materials such as stainless-steel copper, alloys, and zinc are coated in iron oxide through a complex chemical process. Black oxide coating of ferrous materials is a cheaper and relatively easier method to increase efficiency by absorbing maximum laser light. 

Firstly, the rate of light reflection is greatly reduced, hence, the results in UV sensors or IR sensors are not hampered by the excess light that penetrates through them. The black oxide coating is also beneficial since it adds to the thickness of steel even if it’s microscopic, the sharpness of screwdrivers and drills is maintained. Furthermore, fiction and corrosion are reduced due to the wax that is present in the black coating. The wax or oil also makes the material water-resistant as water is the main cause of rusting of metal. 

Process of Black Oxide Coating 

Three types of black oxide coating are present; hot black oxide, mild temperature black oxide, and cold black oxide. All these processes are complex and require professional skills to be carried out. 

The hot black oxide coating includes a hot bath of nitrites and nitrates and sodium hydroxide. The ferrous material is dipped into the hot bath which converts its surface into magnetite. Then the material is dipped into three tanks that contain alkaline cleaner, caustic soda, and water. The caustic soda is responsible for turning it black.  In the end, the material is dipped into oil or wax which acts as a coating material. 

Secondly, the mild temperature black oxide has almost an identical process as the hot black oxide coating, however, the temperature at which the product blackens is different in this case.  This is more efficient since caustic fumes are not released as the product blackens before reaching the boiling point of caustic soda.

Now, let’s move onto the cold coating.  This process is different from the other two since it does not involve any oxide conversion. The deposited copper selenium is used to alter the product. It is simply supported over the material however it rubs off quite easily and provides less resistance in comparison to the other two; hot black oxide technique and mild temperature black oxide process.

The black oxide coating can be used for many materials such as copper and stainless steel but each material requires different coating techniques because of the chemical composition and density.

It has been widely proven by experts that black oxide-coated products last much longer than bare metals. Water is the main factor that causes rusting. The wax coating enables water resistivity hence, unlike other materials, they don’t corrode or rust easily over time.  also due to the wax coating, the cleaning process is much quicker since the harmful substances do not reach the metal core so it takes less time to clean the surfaces without worrying about the core.  The black oxide coating is also beneficial in providing the tools with a sharper edge and causing them to not be done over time. This makes your product more reliable and value-oriented in terms of quality.