ALUMINUM PALMITATE
One of the important metallic soaps. A yellow, massive salt, or a fine white powder of composition Al(C16H31O2)3-H2O, made by heating a solution of aluminum hydroxide and palmitic acid. It is soluble in oils, alkalies, and benzol, but insoluble in water, and is used in waterproofing fabrics, paper, and leather and in paints as a drier. In finishing leather and paper it adds to the gloss. It is also used to increase viscosity in lubricating oils. Another material of the same class is aluminum resinate, Al(C14H63O5)3, a brown mass made by heating rosin and aluminum hydroxide. Aluminum oleate, Al(C18H33O2)3, is a white salt of oleic acid used as a drier. Aluminum stearate, Al(C18H35O2)3, is a salt of stearic acid. It is repellent to water and is valued for waterproofing fabrics and as a drier, and in waterproofing concrete and stucco. It is also used to give adherence to dyes and as a flux in soldering compounds. It is a white, fluffy powder of 200 mesh, soluble in oils and in turpentine. Grades high in free fatty acid, up to 22%, do not gel readily and are useful as a flatting agent and suspending medium in paints. Grades low in free fatty acid have a thickening effect on solvents. Those with 5 or 6% are used in lubricating grease, and those with about 8% are used in paints. Aluminum monostearate and aluminum distearate have similar uses.
ALUMINUM POWDER. Aluminum powder is produced by drawing a stream of molten metal through an atomizing nozzle and impinging that stream with compressed air or inert gas, solidifying and disintegrating the metal into small particles, which are then drawn into a collection system and screened, graded, and packaged. Particle sizes range from —325 mesh (fine) to +200 mesh (granules). In the process, the metal reacts with oxygen in the air and moisture, causing a thin film of aluminum oxide to form on the surface of the particles. Oxide content, which increases with decreasing particle size, ranges from 0.1 to 1.0% by weight. The reactivity and combustibility of aluminum powder require special handling precautions. Dust clouds, having a low ignition temperature—less than 1110°F (600°C)—and low explosive limits, need little oxygen (less than 3%) to be ignited by an electric spark or other ignition sources. Although coarse particles are difficult to ignite, particles in the —200 to +325 range and finer can be quite explosive, even in small concentrations. First used to produce aluminum flake by ball milling for paint pigments, aluminum powder now finds many other uses: ferrous and nonferrous metals production, powder metal (PM) parts, PM wrought aluminum alloy mill products, coatings for steel, asphalt roof products, spray coatings, and vacuum metallizing. Other applications include rocket fuels and explosives, incendiary bombs, pyrotechnics, signal flares, and heat and magnetic shields. It is also used in permanent magnets, high-temperature lubricants, industrial cements, chalking compounds, printing inks, and cosmetic and medical products. Aluminum powder alloy A201AB is used to produce cam bearing caps for dual-overhead-cam auto engines.

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