Well, yes and no. It is "similar" to gun bluing, but not the same. And, when combined with a secondary coating such as oil or wax, it does provide greater corrosion protection that just oiling bare metal.
There are basically two types of rust; red and black. Red rust (ferric oxide, Fe2O3) is our common old junk rust. Black rust or black oxide (magnitite, Fe3 O4) is a specially generated surface oxidation used as the tool coating. If a tool has a surface of black oxide it is much less susceptible to additional rusting as more of the iron atoms are bonded to oxygen atoms. However, it alone does not prevent all further oxidation, so alone it is a somewhat poor corrosion protection. However, if combined with an oil, wax, or lacquer, it is provides an excellent INDOOR corrosion protection; much better than just oil or wax alone. It is NOT GOOD as an outdoor tool protection.
