sorting sreface rust on chassis?

[CaptainCrash1971]

Try this stuff
http://www.rust.co.uk/rust-converters.cfm
It's about 22 quid for a litre which should be enough to do a full chassis. Then you can just paint directly onto it.
You can also water it down to dip pieces, or spray it into the chassis rails to avoid internal rust from working it's way through.
Same company do the epoxy mastic 121 paint for chassis too, so might get a discount on postage.