Black Oxide Coating Thickness

I would like to consider using black oxide but need to know more about the capabilities.

Black oxide coating thickness.

Bluing is a passivation process in which steel is partially protected against rust and is named after the blue black appearance of the resulting protective finish true gun bluing is an electrochemical conversion coating resulting from an oxidizing chemical reaction with iron on the surface selectively forming magnetite fe 3 o 4 the black oxide of iron. Black oxide coating thickness. Black oxide or blackening is a conversion coating for ferrous materials stainless steel copper and copper based alloys zinc powdered metals and silver solder. Services with cincinnati black oxide.

Black oxide is a conversion coating formed by a chemical reaction produced when parts are immersed in the alkaline aqueous salt solution operated at approximately 285 degrees f. How black oxide coating works. For decorative applications and can be used to decrease light reflection. Black oxide coating does not peel from the surface.

One of its advantages over other coatings is. Dipping a metal part into a heated alkaline liquid for a specific period of time triggers the chemical process that forms magnetite on the part s surface. It is used to add mild corrosion resistance for appearance and to minimize light reflection. An adherent black oxide coating on a bearing is reported to improve the reliability and performance of bearings especially in wind turbines 3 16 and hence reduced downtime and maintenance costs.

Thickness of black oxide coating does not exceed 3 10 5 inch 0 75 µm half of which is added to the part dimension and the second half penetrates into the part depth. Only very limited corrosion protection under mild corrosion conditions. A discussion started in 1999 but continuing through 2018. I am outsourcing some components from taiwan and they have a difficult time maintaining a consistent plating thickness using zinc chromate on the steel parts.

Mostly a decorative coating. The point of the black oxide process is to create magnetite fe3o4 an alloy of iron and oxygen molecules on the surface of the metal. A black oxide conversion coating is applied to ferrous alloys when oxidizing salts react with the iron to form magnetite fe 3 o 4 the black oxide of iron. Black oxide penetrates the steel 5 10 thousandths and adds to the part thickness by only 5 10 thousandths providing a hardness of 5 on the mohes scale.

Strong adhesion between the coating and the substrate. To achieve maximal corrosion resistance the black oxide must be impregnated with oil or wax. A typical thickness of the black oxide layer is about one to two micrometers 2 3 10 13. For moving parts which cannot tolerate the dimensional change of a more corrosion resistant finish.