General Dinitrol Rust-off
Rust-Off primer (Dinitrol RC900 spray can)
Rust-Off Primer by Dinitrol, an epoxy coating that converts & binds rust & creates a good surface for subsequent painting 400ml spray or 1 litre tin (RC800) (from Frosts)
Turns rusty metal black, seems to leave clean metal (& any stainless or galved) with a semi-transparent purple coating, and can be overcoated within an hour or so. Spray on any dry, wire-brushed rusty surface after removing heavy scale. Into rusty seams etc is good.
Downside, if any, is that it needs thorough removal before welding or brazing (scurfing, so a good treatment after welding, or longer term temporary prevention, but think twice if welding is following along soon... or mask off any such areas).
HM: Recommended, about £15/can from Frost Auto Parts, lasts pretty well.
Update: RC800 liquid more economical, brush on, 1 litre last forever.
Overcoated with Eastwoods Chassis Black
Combined with Eastwoods Chassis Black finish, excellent for producing a tough finish on parts that have been cleaned, wire-brushed and degreased, but not necessarily sand-blast perfect
An example of RC900 pre-treat on bare wire-brushed metal, + 2 coats of Eastwoods Chassis Black
Brackets are Pure-Zinc spray treated (Weld-Thru)
NB. Frosts are now saying in their blurb that they can supply (at least) two types of EW Chassis Black.. Original and extra tough (but more expensive).