Steel will rust and I would think the air from the diffusers will just quicken that process.. should last for years though..
Shoot some decent epoxy on the steel and let it cure properly, then toss it into the drink. 20 years later it will still look new. With plastic NPT (National Pipe Taper) threads you will not want to use any sealants or Teflon tape. It changes the coefficient of friction that locks this type of thread up and could come loose over time. Just crank it down raw. Some of this stuff will eat plastic so it's best to do it dry.
