Black Oxide Coating MIL-DTL-13924D
Is a conversion coating for ferrous materials, stainless steel, copper and copper based alloys, Zinc, powdered material, and Silver solder. It is used to add mild corrosion resistance, for appearance and to minimize light reflection. To achieve maximal corrosion resistance the black oxide must be impregnated with oil or wax. One of its advantages over other coatings is its minimal build-up.
The benefits of metal blackening are far greater than simply an attractive finish