The Transit is not body on frame construction.
Unlike the Econoline vans, the rear Transit wheeltubs are two piece, with the welded seam facing down towards the tire (Sprinter and Promaster are the same crappy design). None of these vans have any type of supplemental debris shielding in the rear wheelwells. Only the Sprinter (so far) has plastic shielding in the front wheelwells.
The seam sealer in the Transit wheelwells is left as-is, out of the application gun. The sealer is not sprayed or spread out with a brush of some sort. Look reasonably closely, and you will see many gaps and other areas of less than acceptable protection where 2 and 3 pieces of the body structure are joined together at the wheelwell seams. Open the sliding side door, look down, and you will see about 3" of seam on opposite sides with no sealer. There is foam material protruding from a panel joining area at the rear wheelwell from the side facing the front of the vehicle. There is no body cavity wax in the Transit doors, or visible wax on the inside at the bottom of the van wall section.
No one in the USA knows how well the Transit will perform against salt and brine snow removal chemicals, and it will take a couple of years to see what happens.
Unless the metal has a super duty (r)
galvanizing process or an equally awesome e-coat process... maybe the Transit boards will be full of angry rusty Transit owners.
The paint appears to be decent though, and all colors are basecoat/clearcoat.
In the past, aftermarket rustproofing voided the factory corrosion warranty, so do check up on that. Of course, getting the OEM to honor the corrosion warranty is another matter...