Water

PYROPHORIC METALS

DOE-HDBK-1081-94

Spontaneous Heating and Pyrophoricity

Boron Trifluoride and Boron Trichloride

Boron trifluoride and boron trichloride have both been used to control fires in

heat treating furnaces containing magnesium. The fluoride is considerably

more effective. In the case of small fires, the gases provide complete

extinguishment. In the case of large fires, the gases effect control over the

flames and rapid burning, but reignition of the hot metal takes place on

exposure to air. A combined attack of boron trifluoride gas followed by

application of foundry flux completely extinguishes the fire. For details of gas

application, see NFPA 480, Standard for the Storage, Handling, and

Processing of Magnesium.

Inert Gases

In some cases, inert gases (such as argon and helium) will control zirconium

fires if they can be used under conditions that will exclude air. Gas blanketing

with argon has been effective in controlling lithium, sodium, and potassium

fires. Caution should be exercised when using the agent in confined spaces

because of the danger of suffocation of personnel.

Water

When burning metals are spattered with limited amounts of water, the hot metal

extracts oxygen from the water and promotes combustion. At the same time,

hydrogen is released in a free state and ignites readily. Since small amounts of water

do accelerate combustible metal fires (particularly where chips or other fines are

involved), use of common portable extinguishers containing water is not

recommended except to control fires in adjacent Class A materials.

Water, however, is a good coolant and can be used on some combustible metals under

proper conditions and applications to reduce the temperature of the burning metals

below the ignition point. The following paragraphs discuss the advantages and

limitations of using water on fires involving various combustible metals.

Water on Sodium, Potassium, Lithium, NaK, Barium, Calcium, and

Strontium Fires

Water must not be used on fires involving these metals. Water applied to

sodium, potassium, lithium, sodium-potassium alloys (NaK), barium, calcium,

and strontium will induce chemical reactions that can lead to fire or explosion

even at room temperatures.

Pyrophoricity

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