Try barkeepers friend cleaner.
Lysol Lime & Rust Remover Toilet Bowl cleaner, comes in a black squirt bottle. Scrub with Scrub Daddy or Mr. Clean Magic Eraser.
I love Barkeepers Friend for the bathtub. I use the powder and the spray.
I use baking soda and white vinegar solution, its won't scratch the tub
I have a cast iron sink in white. I use a spray kitchen cleaner with bleach to remove stains and Comet with bleach to scrub away stains.