Blackening

Blackening is a surface finish operation that coats the surface of ferrous materials chemically. By this, it creates a strong chemical barrier against humidity and corrosion. Blackening is generally a cheaper option compared to painting and plating.

Blackening uses chemical compounds that stick to the surface of machined metal under consideration. A porous base is created that bonds chemically with the workpiece surface. In cold blackening, that chemical compound is copper/selenium (CuSe).