If a (possible) WTC metal sample is low in Chromium, yet has “abundant Manganese”, then it cannot be mostly structural steel.
This comes from Professor Steven Jones’ analysis of metal samples from the WTC, where he tells us:
Previously molten metal has very little (if any) Chromium yet abundant Manganese* (we rule out molten structural steel (as a major component)
We have no idea if the metal sample is structural steel or not, however it would be helpful to follow the logic. And we’re not sure that we do. The NIST report NIST NCSTAR1-3A, for instance, tells us more about the structural steel specifications at the time the WTC was constructed, and throughout their tables it’s very obvious that Chromium (CR, highlighted yellow) is rarely included, while Manganese (MN, highlighted blue) is much more common.
Fortunately the NIST report NIST NCSTAR 1 3-E covered an analysis of WTC steel samples, and that does explain that some included Chromium (CR):
Chemical analysis of the recovered WTC steels showed a division in the types of steels used. For the lower strength components, Mn and Si were added for strength. Higher strength components contained Cr and Mo additions.
Mass fraction graphs of various components still show Manganese (MN, red) is more abundant than Chromium (CR, green), however.
Perhaps this is unrepresentative. Maybe we’ve missed the bit where they identify the parts of the WTC that have loads of Chromium and no Manganese at all: go read the NIST reports, find out for yourself. But from what we’ve seen to date, finding Manganese without much Chromium really isn’t a surprise at all.
Of course there may be other sources of Manganese, too:
Metallic manganese is used in the manufacturing of steel, carbon steel, stainless steel, cast iron, and superalloys to increase hardness, stiffness, and strength (HSDB, 1995). Manganese chloride is used in dyeing, disinfecting, batteries, and as a paint drier and dietary supplement. Manganese oxide (MnO) is used in textile printing, ceramics, paints, colored glass, fertilizers, and as food additives. Manganese dioxide is used in batteries and may also be generated from the welding of manganese alloys. Manganese tetroxide may be generated in situations where other oxides of manganese are heated in air (NIOSH Pocket Guide, 1995). The annual statewide industrial emissions from facilities reporting under the Air Toxics Hot Spots Act in California based on the most recent inventory were estimated to be 126,107 pounds of manganese (CARB, 1999).
In addition, a Manganese compound called MMT is sometimes used in petrol, although we’re not sure how common that was in the US, circa 2001. And the NCSTAR 1 3-E report points out that the aluminium facade of the WTC was actually about 1% Manganese, and included many other chemicals:
A piece of the aluminum fašade from the World Trade Center (WTC) towers was recovered and available for testing. These pieces fit around the outside face of the column and were one story in length. It was unknown which tower this piece was recovered from. Chemical analysis was conducted to determine the alloy type...It appears that the chemistry would place it in the 3xxx-series alloys (Al-Mn alloy).
Further, another study of the dust around Ground Zero has found Manganese and other elements, but doesn’t appear to see any significance in this. The paper “Characterization of the Dust/Smoke Aerosol that Settled East of the World Trade Center (WTC) in Lower Manhattan after the Collapse of the WTC 11 September 2001”, for instance, tells us:
The levels of many of the elements are consistent with their presence in building materials, including chromium, magnesium, manganese, aluminum, and barium.
Another revealed an increase in Manganese (MN) during the cleanup process:
Hazi also observed a large increase in the fine fraction for Fe and Mn during December 2001, when WTC workers were using a large number of blow torches on the bent steel.
Professor Jones may attach special significance to Manganese, then:
Hence, K, Mn and F are often present in thermite residue, suggesting they are part of a “thermite fingerprint” at WTC.
But he fails to explain why the amount he has discovered is particularly significant, or how thermite is a more plausible source than anything else.