I haven't tried this yet but, Instructables has an awesome looking series on removing rust, using a small automotive charger, rebar, washing soda and wire.

I'm definitely going to give this a try!

[url=http://www.instructables.com/id/E17UQMY28PEQ6T2A5Z/]http://www.instructables.com/id/E17UQMY28PEQ6T2A5Z/[/url]