I stripped a car to metal in preparation for paint. I then used acid rust converter to keep the metal from rusting. Since I didn't have a garage the car still got wet at times and after every rain it was covered in rust again.
Still all that sanding of bare metal must have saved some weight, just like RS Porsche use thinner gauge metal in their panels
Or you could just let it go for that rat rod look. Bare metal actually doesn't rust away that quickly on the exterior of a body.