Ideas to clean a porcelain sink?

If you're talking about cleaning a porcelain sink. And you're talking about hard water stains. You can use a pumice stone picked up at any hardware store and use it to clean the stain out. If you're talking about a chemical stain or something that has really ruined the coating of the porcelain , and you really love the sink you can use a porcelain paint on your sink and then seal it with a porcelain sealant.

Try Barkeeper's Friend - it comes in a powder or a thick liquid and is found in most grocery stores, WalMart, etc. It will clean most stains from Formica, tile, porcelain, etc.

have it professionally refinished.

Seems like you have tried everything. May time to have it refinished or replaced. You can try Rustoleum Tub and Tile Paint kit to refinish it yourself. Prep is the key.

I can't tell from the post what the problem is, but if it's just stains, fill sink with hot water and bleach and let it sit for several hours. If it's soap scum, then use a soap scum remover like Scrubbing Bubbles. Spray it on, let sit for 5 minutes, then scrub gently and rinse.

Hello Tami! If it is a white porcelain sink, try this trick. Line the sink with paper towels and soak them with bleach. Let sit for 30 minutes. Then discard them and rinse the sink with running water. Do not use on colored porcelain as it could fade the color. For colored porcelain, use a mild dish detergent and vinegar or baking soda. The vinegar will clean it with the soap but the baking soda will act as an abrasive if you need to scour the sink a bit. Good luck! !

What is it stained with? Or is it covered with a layer of limescale?