The observations of Barnett, Biederman, and Sisson describe
sulfidation of some structural steel from WTC 7. They say:
“Rapid deterioration of the steel was a result of heating with oxidation in combination
with intergranular melting due to the presence of sulfur. The formation of the eutectic
mixture of iron oxide and iron sulfide lowers the temperature at which liquid can form in
this steel. This strongly suggests that the temperatures in this region of the steel beam
approached ~1000 C, forming the eutectic liquid by a process similar to making a
“blacksmith’s weld” in a hand forge.”9
And they conclude:
“The severe corrosion and subsequent erosion of Samples 1 and 210 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.”
We should take note of the fact that they are saying they have no idea of the rapidity of the
sulfidation and oxidation processes or when they began. They also seem to be aware of the fact
that there were large volumes of red hot metal below the rubble piles. (This is rather interesting
since NIST, their sponsor, claims they are unaware of any such thing. )11
Now consider the problem of the molten metal flowing from the 82nd floor of WTC 2. Some
have suggested that this metal was the eutectic mixture of Fe and S. Let’s discuss that possibility.
We assume that the steel that is cut from the columns is essentially pure Fe. It is melted and
mixes with the thermate reaction products and then flows away by gravity. As the mixture cools,
if the original molten mix was at S < 31.4%, Fe begins to crystallize out. This increases the S%
in the remaining mix. As the cooling continues, the S% increases until it reaches 31.4%, and this
remaining molten eutectic mixture solidifies at 994 C (or 988 C, depending on which
measurement you believe). So unless the original S% was 31.4%, the molten mass is
crystallizing out solidified Fe as it flows downhill and cools. When, in the cooling process, the
molten mass reaches the eutectic composition, it also reaches the eutectic temperature. At that
temperature the remaining liquid gives up its latent heat of fusion and crystallizes as a
9 See Footnote 2.
10 From WTC 7 and WTC 1 or 2, respectively.
11 John Gross, Video presentation at UT Austin, http://www.pnacitizen.org/john_gross_nist_pnac.php
microscopically heterogeneous solid with a (macroscopically) 31.4% S, 68.6% Fe composition.
Once all the material has solidified the entire mass resumes cooling. We thus have a plausible
explanation of why the material flowing from WTC 2 was orange-hot liquid (~1000 C).
However, if the thermate contained only 2% S by weight (as specified for Thermate-TH3)12, that
would not be enough to even produce a eutectic mixture using all the Fe produced in the
thermate reaction, let alone all the added Fe from the cut column. It is not likely that the amount
of sulfur used would have produced a product close to the eutectic mixture; however any
substantial amount of sulfur will usefully lower the melting point of the attacked steel by