Drum corroded in storage.
As a note for future reference, I regularly use a phosphating primer of military origin called Suncorite. Many years ago a company I was working for used an old portion of Bentley chassis and applied many different paint products to sections of the chassis that had been prepared in different ways. The chassis was then placed on the roof next to the tea room window, exposed to all weather. Amongst all of the decaying paints, Suncorite retained it's satin black finish with barely any deterioration, that was over a decade ago! As well as the ability to endure weather the product also has a reasonably high temperature resistance and is ideal for a subtle, almost "oil blacked" finish to nuts and bolts.
Prior to strip
Some cosmetic preparation, retaining a little "Patina"
The pictures below show an innovative little "creatures" larder!
Gearbox awaiting attention.