After searching the interwebs and HBT, I'm having a hard time figuring out what exactly your standard 1/4" Swivel Nut (silver-colored) is made out of. Stainless? Something else with stainless plate?
Leaving my aerator hose & swivel nut/airstone combo in StarSan for a few hours caused the swivel nut to turn a lovely shade of grey/black.
One doesn't want to risk anything when a piece of metal is in contact with wort for at least 30 minutes ... but if a quick dip in something else removes the tarnish and keeps the metal safe for wort-contact (and saves a buck or two), then cheers to that!