I used to apply industrial coatings to aircraft parts for a living. Hard chrome is a very different thing from the coating you see on cheap guns. Hard chrome is the substance you see on the inside of hydraulic cylinders, chrome lined rifle barrels, high speed industrial tooling etc. It is very durable and rust resistant. The coating you see on cheap guns is like the chrome they used to put on car bumpers back in the day. Not very durable or rust resistant.