My paints peeling and fading, what do I do to prevent rust without repainting?

I would see what a body shop would charge to sand and reclear the roof. Or try on your own, but you need to prep it correct it the clear will just peel again.

Looks like something corrosive got on the hood. That would need some sanding, a light skim coat with sanding and feather ( if you don’t want outlines in the paint), then some base and clear the whole hood.