Black finishes are mainly used on screws for functional and aesthetic reasons. Depending on the base material, different processes are used, each involving a different chemical process.

Black Finishes on Steel: Black Oxide Treatment

During black oxide treatment, the surface of steel is deliberately converted in a hot alkaline bath into a thin layer of black iron oxide (magnetite, Fe₃O₄). This layer is firmly bonded to the base material and has virtually no effect on the dimensions of the part.

However, corrosion protection is limited and usually enhanced by subsequent oil or wax treatments.

Black Finishes on Stainless Steel: Chemical Blackening

Stainless steel cannot be treated using the conventional black oxide process because its alloying elements prevent the formation of the required oxide layer. Instead, a chemical blackening process is used to chemically modify and darken the existing passive layer of the stainless steel.

Here, too, a very thin finish is produced with virtually no effect on dimensions, primarily for aesthetic purposes and with only limited corrosion protection.

Why Black Screws?

-Reduced light reflection

-Subtle, high-quality appearance

-Suitable for indoor applications requiring only limited corrosion protection

-Commonly used in furniture, equipment, and machine manufacturing

Important Note

The finishes produced by black oxide treatment or chemical blackening are extremely thin and have no measurable effect on thread geometry or fit. For applications exposed to higher levels of corrosion, additional protective measures or alternative coatings are required.