Tubular steel framework of a class A motorhome

[freedom24]

Hello all,
I recently purchased a 2003 Fleetwood Terra with 10K miles. It has zero delamination, an excellent roof, great interior and exterior with no evidence of water damage. But when pulling off the rear taillights to replace with LEDs, I see that the tubular steel framework is rusted to the point that it crumbled into jagged pieces, when I touched it with a screw driver. So while gently poking holes through the rusted frame work and sanding the rest, all I could do was paint rust inhibitor liquid on the remaining frame work (behind the rear fiberglass wall) area of the taillight mounting locations. Later, I went up top to install a new Coleman Mach 3, and the steel framework around the roof opening (where the AC is mounted) had all BARE (lightly rusted steel frame work). The visible interior section of roof framing----all bare metal with medium to light rust.
I also pulled off the plastic molded piece that surrounds the fuel neck filler tube. And again, bare steel framework that is partially rusted through with holes. So I have to ask-----Does anyone know why Fleetwood would assemble a motorhome with NO protective coating on its framework?
Is this normal practice, or did the builder take short cuts and skip the quality control process in September of 2002. I am honestly astonished! Am I the only one? Why wouldnt they atleast paint the steel framing, before adding on the walls and skin of the motorhome? Anyone else?

Many thanks!

[VanDiemen23]

you live in the south - was this thing parked on the coast for a long time? That kind of corrosion sounds like more than just condensation on bare steel.

[freedom24]

I bought it from an rv dealer, but was able to find a source document that said it was originally purchased in South Carolina. So you must be right-----near the coast.