Well, according to the old British Railways Fire Manual, fires involving metal powders including thermit welding compound, should be isolated and fires in adjoining materials only dealt with, the metals fire left to the fire service.
If you really want to extinguish them yourselves, thwn you need Class D powders (flammable metals are a Class D fire, where class A is solids, B liquids, etc)
There are two main types:
- Sodium Chloride for certain Class D fires, those involving alkali metals such as sodium and potassium, also zirconium, uranium and powdered aluminum, extinguishes a metal fire by fusing to form a crust. This excludes oxygen from the surface of the molten metal; a carbonaceous rafting agent prevents the powder from sinking into the surface of molten metal
- Copper extinguishing agent specially developed by the U.S. Navy for fighting lithium and lithium alloy fires. The copper compound smothers the fire and provides an excellent heat sink for dissipating heat. Copper powder has been found to be superior to all other known fire extinguishing agents for lithium.
These extinguishers have a lance & bell to act as a low velocity applicator to prevent disturbing the metal or the crust being built up.
Normal dry powder extinguishers are not safe for these fires and must not be used (although powder extinguishers filled with Croda Kerr Cetrimax ABC Powder AND a low velocity lance have passed german DIN tests on Class D fires with magnesium, where 12kg of powder puts out 1kg of Magnesium).
If you want Class D extinguishers let me know as the usual catalogue and smaller maintenance/supply companies aren't able to help
