We've been using this recipe for a few years now.
Quite simply it dose the trick and never
fails to amaze me...

Spray it on.
Rinse it off.

Paint it on.
Rinse it off.

I just spray it on and leave it to work it's magic...
Mill Spec Rust Converter - Restorer
500 ml
makes up to 4 Litres
Use neat or diluted.

£10.00 for 500 ml
12.50 Inc Postage