I found this thread on-line earlier today. Like most of the others who stumbled across this, I was looking for help for discoloration of my stainless steel sink.
In my case, I used Whink Rust Stain Remover on a soap dispenser (it took the rust off) and left the brush I had used with the Whink product residue overnight in the kitchen sink. This morning I discovered that my stainless steel sink had discolored where the brush had made contact. It looked awful and I was afraid the sink was ruined.
I emailed Whink and asked them for advice. Here's their response...
Others who have posted in this thread have also recommended Bar Keeper's Friend. I looked around my house thinking I might have some but instead found a product called Aluminum and Stainless Steel Cleaner hiding under my sink. I think I purchased it a long time ago to use on my Calphalon cookware. It is manufactured by Church & Dwight Co. and available from Amazon. It's inexpensive.
Anyway, I tried it and it worked great! It removed all of the discoloration with very little effort. My sink looks better than it did before this mishap.
I hope this post is helpful. Good luck.
Wholesale Rust Remover: Whink Rust Stain Remover Liquid. Convenient liquid formula quickly and easily removes rust stains, with no scrubbing, from white sinks and toilets, colorfast fabric and carpet. Approved by Good Housekeeping Institute. #1 in the US per AC Nielsen reports. Made in the USA. 6oz each. 6 units per case.
Whink Rust Stain Remover: Removes rust stain quickly and easily For white sinks and white toilet bowls, colorfast fabric & carpets Safe on pipes and septic systems
I would use cleaning products such as Bar Keepers Friend, Zud, Whink Rust Stain Remover or The Works. If you prefer a less potent option, make a paste of one cup vinegar (or lemon juice) and 1/2 cup of Borax or baking soda. Leave it for 10 minutes and then scrub and rinse. Test a small area first. Be sure to read all cleaning product instructions thoroughly, too.