So I see all kinds of marketing of new bike frames saying the frames are "ED coated", obviating the need for frame preserver on the inside tubes. All City comes to mind. Further research reveals that ED is electrophoretic deposition and is like a cross between metal plating and powder coating -- dip tank with paint in suspension, bike is charged one way or another, paint particles attract and stick to it.

I was thinking of having and older frame stripped and refinished and started looking around at ED vendors in my area. Not too many to be found, Hardford Finishing is closest to me.

But when they explain the process, I get to this part and it makes me wonder...:

"Ecoat does not protect inside tubes. As a rule, E-coating will only cover the inside of a part 2 times the width of the opening. Much like the Ventury effect in powder coating, the paint material does not attract inside an enclosed area."

So now I'm all kinds of confused, comparing claims of All City vs those of an ED vendor.

Not that it matters much. I'll probably not go this route, just curious about the difference in claims.

That can be explained by electric fields. The tube shields the external field, so the paint won't feel an electrostatic attraction while inside the tube. Except near the opening where the field can sneak in to a depth of about twice the diameter of the opening. So the paint won't stick unless it's near the opening.

All City probably sprays something else down the tubes.

American Motors had a tank to dip whole Nash-Rambler Bodies in to help rust resistance.

The dip tank for bike frames will be much smaller..

While exploring options, I called up a local metal plater, asking about stripping and nickel plating and older frame. Wanted nothing to do with it, said gunk inside the tubes would contaminate his tank. Oh, well...

It's crap. E-coat, even in the car industry, is piss-awful as a standalone anticorrosion protection and only exists at all because its marketed by either the same companies that make paint for cars, or those working hand in glove with them. It's a primer, and only a good primer for the two-pack acrylic paints put on cars. Just an adhesion promoter that you can put on by dunking the monocoque,as opposed to laborious spray routines. Car bodies now rely on the total system protection - trimetal phosphate, then e-coat, then paint. They're harder to damage paint than hen panels were galvanized, phosphated then primed and painted, but the steel rusted much less when you inevitably scored the paint then than now. Toughness of the paint is irrelevant, when the likely cause of paint damage is stone chips which chew even polys, let alone acrylics.

If they offer Oxsilan, now that's a different question altogether ;-)