Lead powder

The primary corrosion product PbHj is unstable and decomposes in a subsequent reaction into lead powder and hydrogen gas. Figures 2-11 and 2-12 are typical examples of cathodic corrosion of amphoteric and hydride-forming metals. 

Tin finds widespread use beeause of its resistanee to eorrosion, or as foil or to provide proteetive eoats/plates for other metals. Properties of lead whieh make industrial applieation attraetive surround its soft, plastie nature permitting it to be rolled into sheets or extruded through dies. In the finely-divided state lead powder is pyrophorie in bulk form the rapidly-formed proteetive oxide layer inhibits further reaetion. It dissolves slowly in mineral aeids. Industrial uses inelude roofing material, piping, and vessel linings, e.g. for aeid storage. 

It has been found that red lead, litharge and certain grades of metallic lead powder render water alkaline and inhibitive this observation has been confirmed by Pryor . The effect is probably due to a lead compound, e.g. lead hydroxide, in solution. Since, however, atmospheric carbon dioxide converts these lead compounds into insoluble basic lead carbonate, thereby removing the inhibitive materials from solution, these pigments may have only limited inhibitive properties in the absence of soap formation. 

Nestlings dosed orally with metallic lead powder daily for 10 days 625 mg/kg BW... 

Nursing rats given diets containing zero, 2000,4000, or 10,000 mg Pb/kg as metallic lead powder Lead-treated rats showed dose-related response to noise stimuli. Blood levels (pg/L) in pups were 40 for controls, 250 for the 2000 mg/kg group, 360 for the 4000 mg/kg group, and 550 for the 10,000 mg/kg group 31... 

Fig. 6.25 Increased burning rates of a double-base propellant resulting from the addition of metallic copper and/or lead powders.

Lead powder can be combined with many binders [5.165], [5.166], It does not affect the stability or viscosity of the paint. Binders that absorb only small amounts of water are particularly suitable (e.g., epoxy resins, chlorinated rubber). When formulating paints based on lead powder, care must be taken not to dilute it with other pigments and extenders by more than 5 vol%. 

The Zeiss-Endter analyzer [87,88] allowed a direct comparison between the projected area of the particle and the area of a reference circle that consisted of a spot of light adjustable in size by an iris diaphragm. The instrument was designed to work with a photomicrograph that could be obtained from an electron microscope to extend the lower size down to around 0.01 pm. Exnor et. al. [89] applied the instrument to size and shape determination of lead powder. A modified instrument, that was rugged and simpler but not as versatile, was described by Becher [90]. 

Lead powder. The oil-suspension of metalhc lead powder is used in the preparation of protective primers for steelwork where it is normally present as the sole pigment. Lead pigments act as a barrier and provide a degree of sacrificial protection similar to that of zinc dust. 

Carborundum sand, aluminum powder, lead powder, glass beads... 

Since 1/3 of the absolute melting temperature is usually sufficient for an effective stress-relief, some materials may self-anneal during the filing. One of the examples is lead (Pb), which is a ductile metal and has melting temperature 601 K. Lead powder self-anneals at room temperature (-298 K), thus producing sharp Bragg peaks in the as-filed state. 

Oxazolidin-4-ones. Difluoro fluoromethane with lead powder. Ti ylides which, in the presence of aide... 

Figure 6.24. Polyurethane formation in the presence of lead powder. Reaction time to reach certain viscosity. [Adapted, by permission, from Caillaud J L, Deguillaume S, Vincent M, Giarmotta J C, Widmaier J M, Polym. / /.,40, No.l, 1996, 1-7.]...

Lead powder was used as a filler in polyurethane. It is clear from the graph (Figure 6.24) that the addition of metal catalyzes the curing process. The reasons for this catalytic effect are unknown. It is suspected that surface impurities may act as a system catalyst but which impurities is not known. 

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