funk de fino
Dreaming of unicorns
The severe corrosion and subsequent erosion of Samples 1 and 2 are a very unusual event. No clear explanation for the source of the sulfur has been identified. The rate of corrosion is also unknown. It is possible that this is the result of long-term heating in the ground following the collapse of the buildings. It is also possible that the phenomenon started prior to collapse and accelerated the weakening of the steel structure. A detailed study into the mechanisms of this phenomenon is needed to determine what risk, if any, is presented to existing steel structures exposed to severe and long-burning fires.
http://911research.wtc7.net/wtc/evidence/metallurgy/index.html
NIST explain the eroded beam from the Tower and also give some examples of sources. They quite categrically state it happened in the pile.
Did you not read it?