Primarily Petroliana Shop Talk Forums Non-Petro Discussions Non-petro Discussion and Showcase Cleaning and removing rust from License plate

Try this stuff from Home Depot, Dave. Not sold at Lowes.
http://www.kleanstrip.com/product/phosphoric-prep-etch
Apply, gently agitate, rinse off after 5-10 minutes. Repeat as needed. Too many times or too long and it will remove the paint as well.
Good luck!
Dave