MSI's Black Chrome is hard, non reflective, abrasion-resistant, heat and corrosion resistant coating of approximately 0.0002" thickness. Black Chrome is applied after heat-treating and all mechanical operations are performed and may be waxed or oiled to darken the surface. The coating itself provides limited corrosion protection but can be enhanced by adding an underplating such as Nickel. Usually produced to Mil-C-14538C Black Chrome is a dull dark gray in color, almost approaching black and approximately conforms to color plate 37038 of the FSN 595. Steel parts with Rockwell hardness in excess of Rc40 are usually stress relieved by baking before plating, and after plating to avoid hydrogen embrittlement.