Redo a bathtub
Rustoleum or Homax tub and tile paint kits. proper prep is the key. Take no short cuts.
You can paint it: https://www.hometalk.com/11633413/paint-your-bathtub
If your tub has any rust spots, sand those places and clean the rust away. There are different kinds of kits for redoing a bathtub. I have used the cheapest. In this case, I think you get what you pay for. We eventually had the tub replaced, but we got about three years out of the old tub. Best wishes to you.