Depending on the degree of rust, I've had great success with Muriatic and Phosphoric acids (Home Depot).
I still use them.
Years ago, I discovered Rusteco...'bought their sample package, then a 2.5 gal. box.
I've had the box for 8+ years now.
I use coffee filters to clean the old stuff - then keep that in separate jars.
It's a good thing.
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Also, at the time, the owner was willing to participate in a group buy.
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http://www.rusteco.com/
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Thanks for the info/link, Mark.
Sweet deal on that Smithy!
I'll have to look into Evapo-rust.