Have you tried Barkeeper's Friend?

For my cleaning clients I have found the product "Lime-A-Way" thick gel formula to work very well. It actually is with the toilet bowl cleaners in your grocery store. I put it on the stain or hard water mark, smoosh it in and let it sit for about 20min. Take a scrubby and wash. Make sure to wear gloves as this is a toilet chemical. I have an old steel tub that had hard water stains and buildup, it took care of mine. Good luck!

The works is a perfect product to remove the good ole "well water ring!" I have found nothing that compares....

If you have a plastic surround and tub system, it may be inpossible to remove the stains in the plastic. You need to be careful with any abrasive type cleaners, as they will scratch the surface of the offended material and cause even more build up as the scratches catch all the stuff in the water.

The Lime Away worked great on my toilets in Vegas. The house we bought had been sitting empty for a long time, and with the extreme hard water, there were rings in the toilets that nothing would touch. The lime away gel worked wonders, with a 3M green scrubbie pad.

The Works Shower Spray. Some Retailers don't carry it in a pray bottle, so I have a reg old spray bottle that I pour it into. It cleans the rust and limescale right out of my shower and tub. Our shower will "turn" within three days if I don't use it.... (and I have tried so many products! Always go back to The Works) Use it in the toilet bowl cleaner for the toilets too.

There is a product available @ Walmart and some other grocery stores that works absolute WONDERS on these rust stains. The name of the product is WHINK. It comes in a small bronze colored plastic bottle. It doesn't smell very pleasant, but it works fantastic.

whink rust remover

Whink will for sure do the trick. I even used it on my hair to remove the rust. Just a quick rinse and the orange was gone and my hair was fine other than needing condishing.