If you are really being paranoid you could use simple brass bushings, but as previous post says, you don't normally use spring winders in sea water!

More importantly, with a mini lathe and a somewhat rusty starting position, I would suggest avoiding what is often a difficult material to machine (stainless) and use something like free-cutting mild steel - EN1A or equivalent, or even a leaded FCMS if you can find it easily. There are enough variables already with speeds, feeds, depth of cut, tool sharpness and angle, etc, so using something which is easy to machine to a good finish means you have removed one problem area. Whatever you do, stay away from odd bits of steel, old bolts, and so on of unknown origin as some of this stuff is really difficult to get to a good finish. And FCMS will be quite strong enough for your job, I suspect. Good luck!