Black Coating on most restoration sheet metal, What is it?
It’s called EDP, which stands for Electro Deposit Primer and it makes an excellent primer under your paint job. As you probably know, factory paint back in the 60’s and 70’s was usually just sprayed onto the surfaces that could be reached by a spray gun. But this left may blind areas behind braces, etc., completely bare of any paint protection. Hence, many cars rested within a few years. But EDP coating is applied electrically, almost like a plating process.
This excellent rust-resistant coating reaches every nook and cranny, for unparalleled corrosion resistance. The only surface preparation required is a light scuffing of the surface for better paint adhesion. No stripping is necessary. The panel is protected from rust as long as the EDP coating remains under your paint.