2 7/16" Insert Bearings OUC212-39

OUC212-39 Insert Bearing?has a property that contains black oxide and specific characteristics that makes it ideal for certain applications. As for appearance it is used to add mild corrosion resistance. Black oxide consists of a coating for ferrous materials like copper and any copper based alloys, powdered metals, zinc, and silver solder.?
Conversion coating is formed by a chemical reaction produced when parts are immersed in the alkaline aqueous salt solution operated at 285 degrees F.