I'm taking my seats apart to repack the bolsters and noticed some pretty bad looking rust. I poked at it with a screw driver and some flaked off but the metal seemed solid.

I have some Rust Cap around, think I should give it a spray?

https://i.imgur.com/pOhODMZ.jpg

 

I took my seat pans out and used rust remover then painted them

 

Clean them up before you paint them. Besides allowing the paint to adhere better it will remove any salt that might be on there.

Be sure to use a primer before painting it. You want to get good paint adhesion. Your interior appears to be getting a little more moisture than usual.

I realize that it looks bad but this is mostly surface rust. Seat frames are not considered to be exposed to the elements so are typically not heavily protected from corrosion. This is not just the case on the S2000 - all manufacturers do it this way.