How do I strip cast iron guttering?

I have some reclaimed cast iron guttering that I want to fit on the house. It is old, rusty and covered in layers of paint. How do I remove all the rust and paint to get back to clean bare metal, as quickly and cost efficiently as possible, anyone got ideas? I assume a chemical dip will be the best way, but what is in a chemical dip, what are the actual chemicals I'd need?