The burnishing process is used to blacken iron and steel.
Black and uniform coatings of iron-ferrous oxide Fe (Fe02)2 are obtained, which are an integral part of the base metal; they withstand severe deformation without flaking.
Beautiful black and shiny finishes are obtained on polished surfaces, while opaque and anti-reflective finishes are obtained on chemically attached or sandblasted steel.
Burnishing is a product that can also blacken steels with a low or high carbon content, alloy steels with a low percentage of alloys and even some cast irons.
The coatings obtained with the burnishing treatment have a moderate resistance to corrosion (2-6 hours to salt spray) and comply with the American Military Specifications MIL-C-13924A, Class 1.

Generally, the lower the carbon content of the steel, the higher the corrosion resistance.

Resistance to corrosion can be increased through treatment with oil, wax or paint.

Treatment using burnishing salts: 138-143°C.

Blackening process for stainless steel and high-alloy steel.

Top-black, by means of an effective surface oxidation process, blackens stainless steels and other steels that are normally difficult to blacken.

Top-black produces a black oxide and sulphide film, the gloss of which depends on the degree of preparation of the underlying surface. The size of the blackened parts can undergo maximum variations of 0.25 micron, the thickness of the black film varies between 1.5 and 2.5 micron.