How do you seal cast iron with a clear coat?

Answer 1

The best way is to sandblast it, then wet it , and allow it to rust for a couple of days, and then brush on 2 coats of a combined rust converter/sealer. Use the type that contains ferric tannate, not phosphoric acid. It will turn it black and glossy, and lasts for years. I once did an old wrought iron gate this way, and it worked beautifully.