If it's a porcelain sink this post might help

https://www.hometalk.com/871709/how-to-remove-rust-stains-from-tub

How to Remove Rust Stains From Tub

Hi Carolyn, here's a handy guide that will help you get rid of those rust stains - https://homeguides.sfgate.com › rust-out-sink-50684

CLR cleaner, or Wink

Porcelain or stainless steel?

Hello. I have had good results using CLR on rust and calcium stains.

Barkeeper's friend and magic eraser

Here's a post that might help - https://www.plumbingprofessors.com/water-issues/iron-stains-on-sink/#targetText=Wet%20an%20old%20toothbrush%20with,effective%20at%20removing%20rust%20stains.