How thick is the porcelain on a modern bathtub?

I can't see the rust stain your speaking of, but I wouldn't start with removing the coating in order to get rid of it. I have used Lime-Away toilet bowl cleaner gel on tough rust stains on items other than just toilets. I apply it and let it sit for a minute or so, and then use a non-scratch (blue) Scotch Brite scrubbing sponge. read more

First off, modern enamel tubs are not very scratch resistant. Anything you do with sand paper or a pumice stone will probably leave a mark. A fairly safe alternative, that may or may not get rid of the stain, is a paste made of baking soda and hydrogen peroxide. read more

Porcelain tubs, which are actually formed steel or cast iron enameled with porcelain, are one of the most common bathtub options. Whether you choose simple or sophisticated, porcelain bathtubs are a good starting point for your bathroom redesign. read more