Frame was acid dipped twice before they galvanized it. Most of the outside surface is pretty good, and even most of the inside surface. The areas that are not so good were definitely clean of all the old rust by the acid dip, it's just that the zinc didn't take in a few areas. I can only assume it was air bubbles trapped inside the frame or the flux dip didn't quite get all the acid off or something. I'm going to try to rig up a wire brush on my sawzall and see if I can't hit the spots inside that got missed. I have read quite a bit about "cold galvanizing" and though not the same as hot dip, it may be more than sufficient in these areas. While I do understand that the bond strength and coating thickness is quite a bit higher with hot dip, the life span and adhesion strength appears to be more than sufficient for the cold process if applied properly. The basic purpose of the zinc is to be anodic to the steel. As long as there is zinc consistently present on the surface, it will galvanically protect the steel from corroding. It does not matter if this is applied hot or cold, the galvanic protection is provided regardless. Hot dip provides a thicker layer of protection. I can do that by applying multiple coats. The downside to cold galvanizing is the surface finish is not consistent with the hot galvanizing, but inside the frame that won't matter.
I'm still undecided as to which way I will go with this, a suppose after doing a few tests with the cold product, I can still decide to strip and re-dip.
As for an overcoat with POR-15... Well, no - but I do have a gallon of chassis saver that was my original intent. So, I may still go that way for an additional layer of protection, but that's hard to shoot on the inside of the frame (and besides, then no one would see that it's galvanized!)
I'll add some close up shots of both the good areas and the bad so you folks can see a little more of what I am talking about.