Also commonly used inside engine/tranny cases to assure the case surface is sealed to stop oil weeping through flaws on the case casting as well as stopping any debris in the case casting from coming loose and getting into the engine.
I have a lifetime supply of glyptal you are welcome to a few ounces of if you'd like to send back your can. I can bring you some at d'port along with the kicker tab I owe you.
It works best if you can bake it after wards at 300-350 for two hours.
Aluminum, not silver, rustoleum works a treat too.