Galvafroild is one such product in the large range of cold galvanising paints.
It's a great paint, provided that the metal being painted has nice coat of surface rust
If the surface is clean & bright, it is next to useless as are the likes of Hammerite.
These products are designed to be painted onto a rusted surface !!
If your chassis is still clean & bright, a healthy coat of etch primer will do niceley
