I use pumie stick on ours, it works really well! It is not safe on fiberglass, but great on solid surfaces like porcelain.
CLR should do the trick!
Hi Debbie, Try removing with Limescale remover or vinegar soaked cloth left overnight. If rust is still a problem - use WD-40.
The best rust remover I ever found is Bar Keepers Friend. It won't hurt stainless steel or sinks and tubs. You can find it where they sell Ajax and Comet cleansers. Good luck Debbie!
I also use Bar Keepers Friend for lime and rust stains.
Try a pumice stone. If cleaners aren't working, this might.
Comet with bleech and baking soda worked for me
The Works toilet bowl cleaner. Original thin one. Test area first.