Hi you could have a go with this;
I would be really interested to see if it does work. I sell a US quart on my site
for 11.99 but if it dosn't work happy for you to send it back and I will provide a full refund.
(Click on Rust Treatment)
A safe, acid free rust remover. Removes rust, not metal. Leaves metal ready to paint, plate or powder coat. So gentle, it's suitable for engine parts. Parts can remain in contact with Rust Dissolver without damage. Harmless to copper, brass, aluminum, solder, lead, plastic, rubber, seals, wood or vinyl. Will not remove paint and chrome that adheres to the surface. Removes blueing and other oxide coatings. Rust Dissolver works as long as the surface is wet.