The possibility of corrosion of the storage and distribution equipment induced by halon-like agents has been studied by Ricker et al.4 as reported in the NIST document cited above. These authors document studies that indicate that the halon-like agents do not pose serious corrosion problems for metals likely to be employed. Again, specific tests are recommended before implementation of materials choices.

Effects on Plastics and Other Organic Materials

The halon-like alternative agents tend to be chemically inert under most anticipated storage and discharge conditions. They would not be expected to exhibit deleterious effects on organic materials present, for example, in equipment or in protected spaces. Examples of organic materials that may be of concern include wire insulation, packaging for solid-state circuitry, circuit boards, floor coverings, paint, furniture coatings, and so on. Machinery spaces aboard naval ships, in general, have less exposed organic material than is typical of other occupied spaces.

Owing to the short exposure time associated with agent discharge in a fire fighting incident, no significant chemical deterioration of exposed organic materials is expected. A mode of failure called environmental stress cracking does exist, and it may be prudent to conduct specific tests on relevant plastics under stress in the presence of the agent in critical areas such as wire insulation. For materials used in typical shipboard machinery spaces, the likelihood of material failure resulting from agent discharge is very low. The reader is referred to the Modern Plastics Encyclopedia5 and a document from the American Society for Testing Materials6 for more detail.

Effects of Discharged Agents on Metals

During flame extinguishment, some acid is formed by the decomposition of halons and halon-like alternative agents. This effect is smaller when the time to extinguishment is shorter. Thus, the release of a larger quantity of agent can result in a smaller quantity of acidic decomposition by-products such as HF.

References

1. R.D. Peacock, T.G. Cleary, and R.H. Harris, Jr., pp. 643-668 in Evaluation of Alternative In-Flight Fire Suppressants for Full-Scale Testing in Simulated Aircraft Engine Nacelles and Dry Bays, NIST Special Pub. 861, U.S. Department of Commerce, Washington, D.C. (1994).

2. R.H. Harris, Jr., Fire Suppression System Performance of Alternative Agents in Aircraft Engine and Dry Bay Laboratory Simulations, Vol. 1, NIST Special Pub. 890, pp. 249-403, U.S. Department of Commerce, Washington, D.C. (1995).

3. Evaluation of Alternative In-Flight Fire Suppressants for Full-Scale Testing in Simulated Aircraft Engine Nacelles and Dry Bays, W.L. Grosshandler, R.G. Gann, and W.M. Pitts, Eds., pp. 729-763, U.S. Department of Commerce, Washington D.C. (1994).

4. Evaluation of Alternative In-Flight Fire Suppressants for Full-Scale Testing in Simulated Aircraft Engine Nacelles and Dry Bays, W.L. Grosshandler, R.G. Gann, and W.M. Pitts, Eds., pp. 669-728, U.S. Department of Commerce, Washington D.C. (1994).

5. Modern Plastics Encyclopedia, McGraw-Hill, New York (1996).

6. American Society for Testing Materials (ASTM), Resistance of Plastics to Chemical Reagents, D543, ASTM, West Conshohocken, Pa. (1995).



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