Here's a photo of the frame rail in question. The big hole is for the steering box shaft and the black vertical bars are the original frame finish from the tapping plates used to hold it on.
Frame Rail I haven't taken out any rivets, but just about every bracket that I can unbolt (spring stops, etc) have this black finish.
I would think that the FAQ I referenced is accurate, just want to get a solid confirmation (photo of frame in a paint booth, or in an acid dip).
This was also part of the FAQ:
"All the major manufacturers use a form of a seven stage process before priming.1. Hot detergent wash to remove grease and oils. 2. Water rinse to remove the detergent, since the detergent interferes with acid. 3. Acid wash to remove scale and open pores in metal. 4. Water rinse to remove acid. 5. Zinc phosphate acid treatment for corrosion protection and paint adhesion. 6. Water rinse to remove acid. 7. Bake dry.This is followed by a primer coat of melamine polyester resin (Japan), polybutadiene (Europe), or a polyester or epoxy ester system (USA)."
But its not clear if this is a modern technique or from the 40-50s time frame.
