Which frame? You don't know that. Where are the reports?
I don't want to argue with you because on 9/11 I feel we have very few differences... however on the "rust on frame" issue I'd play devil's advocate and surmise it's not up to anyone to prove rust may have been a problem, but to prove that it wasn't. The building's exposure to coastal salt air, for 40 years, the lack of galvanizing or other means (like coatings) in the steel frame combined with the architecture with aluminum cladding attached to, and hiding, steel- provide a perfect formula for dissimilar (galvanic) metal corrosion.
Someone said the towers were "well maintained" but I doubt that maintenance involved removal of the entire cladding every decade or so to inspect electrical insulation between cladding and frame even if such a method was employed (it commonly is)
Even if it is, moisture gets between the layers and conducts electricity between them.
Unfortunately my search for actual data on this is stymied by the results being fouled by countless truther sites claiming this was the reason Larry/Bush/Jews/Aliens had to implode the towers.
So in short galvanic corrosion is a guaranteed reality with this mix of materials in that environment, pictures of the construction era show a light coating of rust all over the structure as it went up so we know it was unprotected. (four years in the Navy doing aircraft maintenance on a carrier, as well as living the last 20 years within 100 yds of the ocean, proved to me all ferrous metal corrodes but quick despite your best efforts) They may have provided an electrical insulating method in the attachments, I'd like to see what it was. Most structures that would be at such a risk have a limited design life, everyone knows rust is going to happen, you gamble that it doesn't become a serious issue until the building or structure is obsolete for other reasons, and you aggressively coat (paint) everything you can see and reach.
I'm sure people in the SF Bay Area are loathe to think of it, but the GG bridge is likely a candidate for some serious hidden corrosion. Oh they paint the hell out of it. What they can access. (end to end yearly, IIRC)
In the end I think rust was in no way a factor in the collapses, unless it was REALLY out of hand. It WAS muslims, planes and fires.
However I believe when some of us debunkers take a glaringly obvious fact- that galvanic corrosion in areas with limited access or view, is common and inevitable- and refuse to acknowledge it, we approach truther tactics.
A disclaimer:
If rust WAS a problem, BTW, you'd see evidence of it in the rubble- so maybe it wasn't a problem at all... and maybe this is one of those little sins I think truthers cover up with all their stupidity, like the inferior sprinkler systems or inadequate egress. Just try to investigate it without being repelled by the wall of truther lies- and those who'd have their butts in a sling for allowing rust on the building breath a sigh of relief.