Coating for Heat Radiation from Molten Metal

A. I second what Mr. Smith said.

I dimly recall hearing that black chromium was used for solar panels. Sounds pricey. A manganese phosphate conversion coating might work, that would be much cheaper.

Not sure of the thermal stability of either.

It is not clear as to what exactly you are trying to do though your application appears to be similar to concentrated solar collectors where the the collector can attain pretty high temperatures. Plenty of published literature is available for such collectors. Generally incident radiation would be at lower wavelengths corresponding to source temperature while the collector emits at longer wavelengths corresponding to its temperature which would be lower than that of the source. Coatings are designed to have high absorption at lower wave lengths and low emission at longer wavelengths. Adhesion, temperature stability etc are other important issues. Such coatings are generally applied by PVD techniques.

Hi Sudindra
I do not know Thermalox 250. Their literature mentions 400 °F. That is about 205 °C and a long way short of your 450 °C requirement. It is asking a lot for any organic coating to stand that temperature although some automotive coatings are sold for exhaust pipes. Why not try a sample.
If you want to stick with a spray on coating you might try one of the graphite based dry film lubricants.
I would stick with my original suggestion of black oxide. It is chemically bonded to the steel and it is stable (formed) at high temperatures. In fact, you may find that simply exposing your panel to the furnace may produce the oxide spontaneously. Or apply a thin coat of oil and expose to the furnace. It will cost you nothing to try.