How do you clean the rust out of a cast iron bath tub?

Chemically speaking, phosphoric acid is the key for this because it will react with the rust. An added benefit is that it will react with any hard water build up as well. The problem will be solved without trying to grind it off with a pumice stone.

There are likely to be several sources of this type of product. We make one of them, and there are some before and after photos submitted by our user community.

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