I brought my shell and subframesto be chemically dipped.
Very happy with the result. I put some pictures in my thread, please have a look if interested. No rust anymore, even in the boxed sections like sills and rear panels. I also know that every area has been derusted, like the A, B C posts.
The car has been washed off with water and some phosphatic acid to protect it a bit. Since October 2019 i am doing the welding which the car is in need.
To be honest it is rusting nicely again as there is no real protection but I expected much worse.
When the welding work will be done I will bring the shell back to be acid dipped once again to remove the surface rust, wash it off and then e-coat.
Afterwards I will do the usual paint preparation, stonechip the underside, treat the bos sections and maybe let some fresh oil run into the seams. I believe this will be quite a good rust protection for the next decades.
yes, it will be very expensive regarding the potential value of the car, but I want to have properly done and it is a keeper.
I know a garage restoring old Citroens doing exactly the same for each and every car they do. Only that they do the e-coat before repairing the shell, which is in both directions arguable.
About sanding the car there are also pros and contras.
From my experience there are always mixed ideas about how to restore a shell. In fact the ultimate method would be to reduce it in parts, treat every single panel and assemble it again.
God knows how much this would cost.
cheers
Gilles