Oxynitriding / Oxynitrocarburizing transforms the very top portion of the white layer obtained with either Nitreg® or Nitreg®-C technologies into a complex spinel type structure consisting mostly of Fe3O4 type of iron oxide. As a result, the post-nitriding oxidation treatment has a net effect of enhancing the corrosion resistance of an already nitrided component. This integrated process (i.e. Nitreg® + ONC® or Nitreg®-C + ONC®) simultaneously enhances corrosion and wear resistance of steel, while giving the surface an attractive dark or black appearance, expressly desired by many customers.