Smoke corrosivity

Taking into consideration the relative order of corrodibility, it is preferable to describe corrosive damage as attributable to certain agents rather than to the indefinite characterization smoke. Corrosive agents can be placed into four major groups, namely, oxygen and oxidants, acidic materials, salts, and alkalis. 

Hirschler, M.M., Disscussion of smoke corrosivity test methods Analysis of existing tests and of their results, Fire Mater., 1993, 17, 231-247. 

W. Scharf, USP 2995430(1961) CA 55, 26450(196l)(Composite ptopnt, contg DEGDN, having reduced flash, smoke corrosion props) 23) CondChemDict(196l), 376 24) Sax(1963), 711 25) Urbanski 2(1965),... 

Wire coating high continuous-use temperature, flexibility (i.e., silicone PEI copolymer), ignition resistance, low smoke, and low smoke corrosivity... 

Before discussing the special effects of fillers that are active fire retardants, it is useful to recognise that the addition of any particulate, non-combustible, filler to polymers can considerably affect their thermal stability, resistance to ignition and combustion, and the amount and nature of the combustion gases in terms of smoke, corrosion and toxicity. The main general effects are ... 

Hirshler M.M., Smoke Corrosivity Technical Issues and Testing. In Fire and Polymers II, Materials and Tests for Hazard Prevention, G.L. Nelson, (Ed.), ASC Symp., 21-25 August 1994, Washington DC, Chapter 34, pp. 553-578, ACS, Washington DC (1995). 

The industrial value of furfuryl alcohol is a consequence of its low viscosity, high reactivity, and the outstanding chemical, mechanical, and thermal properties of its polymers, corrosion resistance, nonburning, low smoke emission, and exceUent char formation. The reactivity profile of furfuryl alcohol and resins is such that final curing can take place at ambient temperature with strong acids or at elevated temperature with latent acids. Major markets for furfuryl alcohol resins include the production of cores and molds for casting metals, corrosion-resistant fiber-reinforced plastics (FRPs), binders for refractories and corrosion-resistant cements and mortars. 

Corrosion Resistant Fiber-Reinforced Plastic (FRP). Fiber glass reinforcement bonded with furfuryl alcohol thermosetting resias provides plastics with unique properties. Excellent resistance to corrosion and heat distortion coupled with low flame spread and low smoke emission are characteristics that make them valuable as laminating resins with fiber glass (75,76). Another valuable property of furan FRP is its strength at elevated temperature. Hand-layup, spray-up, and filament-win ding techniques are employed to produce an array of corrosion-resistant equipment, pipes, tanks, vats, ducts, scmbbers, stacks, and reaction vessels for industrial appHcations throughout the world. 

Techniques for handling sodium in commercial-scale appHcations have improved (5,23,98,101,102). Contamination by sodium oxide is kept at a minimum by completely welded constmction and inert gas-pressured transfers. Residual oxide is removed by cold traps or micrometallic filters. Special mechanical pumps or leak-free electromagnetic pumps and meters work well with clean Hquid sodium. Corrosion of stainless or carbon steel equipment is minimi2ed by keeping the oxide content low. The 8-h TWA PEL and ceiling TLV for sodium or sodium oxide or hydroxide smoke exposure is 2 mg/m. There is no defined AID for pure sodium, as even the smallest quantity ingested could potentially cause fatal injury. 

Specifications for gas turbine fuels prescribe test limits that must be met by the refiner who manufactures fuel however, it is customary for fuel users to define quality control limits for fuel at the point of delivery or of custody transfer. These limits must be met by third parties who distribute and handle fuels on or near the airport. Tests on receipt at airport depots include appearance, distfllation, flash point (or vapor pressure), density, freezing point, smoke point, corrosion, existing gum, water reaction, and water separation. Tests on delivery to the aircraft include appearance, particulates, membrane color, free water, and electrical conductivity. 

A solution of sulfur trioxide [7446-11-9] dissolved in chlorosulfonic acid [7990-94-5] CISO H, has been used as a smoke (U.S. designation FS) but it is not a U.S. standard agent (see Chlorosulfuric acid Sulfuric acid and sulfur trioxide). When FS is atomized in air, the sulfur trioxide evaporates from the small droplets and reacts with atmospheric moisture to form sulfuric acid vapor. This vapor condenses into minute droplets that form a dense white cloud. FS produces its effect almost instantaneously upon mechanical atomization into the atmosphere, except at very low temperatures. At such temperatures, the small amount of moisture normally present in the atmosphere, requires that FS be thermally generated with the addition of steam to be effective. FS can be used as a fill for artillery and mortar shells and bombs and can be effectively dispersed from low performance aircraft spray tanks. FS is both corrosive and toxic in the presence of moisture, which imposes limitations on its storage, handling, and use. 

With the increasing emphasis on energy conservation and environmental considerations, additives for fuels that can correct combustion-related problems have aroused considerable interest. Many commercial fuel additives are combinations of organometaHics, dispersants, emulsifiers, and carrier solvents. The organometaHic, often a metal soap, acts as a combustion catalyst, increasing efficiency with reduction of smoke, deposits, and corrosion. 

Materials The damage that air pollutants can do to some materials is well known ozone in photochemical smog cracks rubber, weakens fabrics, and fades dyes hydrogen sulfide tarnishes silver smoke dirties laundry acid aerosols ruin nylon hose. Among the most important effects are discoloration, corrosion, the soiling of goods, and impairment of visibility. 

Use of excess air levels of 5 percent or less has been shown to reduce fuel ash corrosion in furnaces, most likely by stabilizing the vanadium as a refractory suboxide, VO2 or V2O3. Utility plants have had some success using this method to control vanadium ash corrosion. However, practical application of excess air control in refinery and chemical plant operations is difficult, and has not been particularly successful. Problems with particulates, smoke, pollution, and flame control are encountered unless the necessary expensive control systems and operator attention are constantly available. 

In addition to the inherent flame resistance, the polymers are also interesting because of the low smoke generation and low levels of toxic and corrosive emissions when exposed to fire. 

Not only does the material have excellent resistance to burning but smoke emission values are reported to be much less than for fire-retardant polyester resin. The laminates are being increasingly used in situations where corrosion is associated with organic media, where corrosion is encountered at temperatures above 100°C as in fume stacks and where both fire retardance and corrosion resistance are desired as in fume ducts. 

These materials are developed from the polyetherimides introduced by General Electric (see also Section 18.14.2). At the time of writing one grade, Ultem Siltem STM 1500, is being offered. It is of particular interest as a material for wire and cable insulation, as it not only has excellent flame resistance coupled with low smoke generation but also avoids possible toxic and corrosion hazards of halogenated polymers. This can be of importance where there are possible escape problems in the event of a fire, such as in tunnels, aircraft and marine (particularly submarine) vessels. 

BOMBS, SMOKE, CONTAINING CORROSIVE LIQUID, NON-EXPLOSIVES 2028 ... 

This is a clear liquid that vaporizes and, on contact with damp air, combines with w ater to produce a dense acid mist. Titanium tetrachloride can be painted on to surfaces, such as fume cupboard sills, from which it will evaporate over a period of several seconds showing the airflow patterns close to the surface. (Airflow patterns close to a surface could also be visualized by fastening short filaments of wool or cotton to the surface). Titanium tetrachloride can also be used, when soaked onto a cotton swab, in a similar way to a smoke tube. It is a simple and inexpensive method but the production of smoke, which is toxic and corrosive, is uncontrollable. 

These methods are the simplest, cheapest, and practically most accessible for airflow visualization. They are sold in the form of small glass tubes or plastic bottles through which air is pumped manually. Time for use of one unit is typically one hour or up to one day. One drawback of these two principles is the fact that the emitted smoke is strongly irritating if inhaled and also corrosive. Therefore, they must be used with some care, but this will normally not lead to any major re strictions. Another limitation is the low amount of smoke that is emitted. 

Si, and stannic tetrachloride. An effective smoke agent, whether it be mechanically dispersed from an aircraft spray tank or vaporized thermally, is a mixt of S trioxide and chlorosulfonic acid (FS smoke agent) which upon hydrolysis forms sulfuric and hydrochloric acid dispersions. Of course, all such formulations are highly corrosive, and, if not outright toxic, then conducive to pulmonary edema... 

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