Metamars:

Is this what you want:

Calculation of the Heating Effect of a Thermite Coating on a Steel Column:

The thermite reaction of interest is Fe2O3 + 2Al = Al2O3 + 2Fe

The energy released by 1 kg of a stoichiometric mixture of ferric oxide and aluminium undergoing this thermite reaction is 3988 kJ/kg.

Consider a 100-micron layer of this mixture coated on a steel column on an upper floor of one of the Twin Towers.

For simplicity we shall assume the coated surfaces are on all four sides of a box column that is 20 cm wide spanning one 3.7-meter high floor. Thus we have a total surface area per column of 3.7 x 0.2 x 4 = 2.96 m^2. (We could also consider an equivalent wide-flange column)

The volume of our 100-micron coating is then = 2.96 x 100 x 10^-6 m^3 = 296 x 10^-6 m^3

The density of the thermite mixture is assumed to be ~ 4500 kg/m^3, so the mass of our thermite coating per one floor column length is = 4500 kg/m^3 x 296 x 10^-6 = 1.332 kg

Using the 3988 kJ/kg heat release of the thermite reaction we have a total heat release per one floor column length of 1.332 kg x 3988 kJ/kg = 5312 kJ.

Next we need to calculate the mass of steel that was exposed to this 5312 kJ of heat energy.

Column specifications for the upper floors of WTC 1 indicate the typical mass of structural steel per column per floor was about 1500 kg.

The heat capacity of steel is 0.45 kJ/kg so 1 kg of steel requires 0.45 kJ to be heated by 1 deg C.

Therefore 1500 kg requires 675 kJ.

The heat released by our 200-micron layer of thermite is 5312 kJ. Thus the expected temperature increase is (5312/675) x 1 deg C, or about 8 deg C.

Newton:

Ah yes, the old rocket-fuel coating idea is much better because the thermal insulation coating was say 1 cm thick while the nano-thermite coating appears to be only 100-microns or 100 times thinner.

If ammonium perchlorate is as energetic per gram as nano-thermite, the equivalent temperature increase is 100 x 8 deg C or 800 deg C - more than enough to cause some serious heat weakening.