The simple aluminum body is a malleable, silvery metal, slightly
alterable to air, note 1 and not very dense. It is the most abundant metal in
the earth's crust and the third most abundant element after oxygen and silicon;
it represents on average 8% of the mass of materials on the solid surface of the
planet. It is, as a general rule, too reactive to exist in its native state in
the natural environment note 2: it is found combined with more than 270
different minerals. Its main mineral is bauxite: it is present in the form of
hydrated oxide from which alumina is extracted. It can also be extracted from
nepheline, leucite, sillimanite, andalusite and muscovite.
The exposed metal is immediately self-passive by oxidation, even in unfavorable conditions: a layer of impermeable Al2O3 alumina a few nanometers thick protects it from corrosion (the favorable conditions are essentially: not very warm, not very humid, little polluted, not very salty; suitable quality alloy). The oxidizability of aluminum must be technically controlled in industrial processes; it is used in some of them (the two main ones are rapid amplified forced anodic electrolytic oxidation and rapid clogging by hot hydration).
Its lightness, its resistance to corrosion, its varied shaping and its lasting coloring make it an important material and widely used in industry and crafts, despite the technicality of its implementation, in pure or alloyed form, especially in aeronautics, transport and construction. Its reactive nature also makes it a catalyst and an additive in the chemical industry; it is thus used to increase the explosive power of ammonium nitrate.
In 1807, Humphry Davy, after discovering that sodium and potassium entered the composition of alum (astringent substance used to fix tinctures), supposes that there is also another metal, which he baptizes "Aluminum" (in Latin, "alum" is called alumen) 16. Pierre Berthier discovered in a mine near Baux-de-Provence in 1821 an ore containing 50 to 60% of aluminum oxide. This ore will be called bauxite.
In 1825, Danish chemist and physicist Hans Christian Ørsted succeeded in producing an impure form of the metal. Friedrich Wöhler deepens the work of Ørsted in 1827. He isolates aluminum by the action of potassium on aluminum chloride, obtaining a gray aluminum dust. He is the first to highlight the chemical and physical properties of this element, the most notable of which is lightness.
The French chemist Henri Sainte-Claire Deville improved in 1846 the method of Wöhler by reducing the ore by sodium. In 1854, he presented the first aluminum ingot obtained, in the molten state, by chemical means to the Academy of Sciences17. He published his research in a book in 1856. This method is used industrially throughout Europe for the manufacture of aluminum (especially in 1859 by Henry Merle in his factory in Salindres, cradle of the company Pechiney), but it remains extremely expensive, producing a metal whose price was comparable to that of gold (1,200 and 1,500 F gold / kg and silver 210 F / kg only). The metal is then reserved to make luxury jewelry18 or goldsmithery reserved for an elite. This is the case for the honor coupes (made in particular by Paul Morin and Cie) 19 and works of art made for the imperial court of Napoleon III20. The latter receives his distinguished guests with aluminum cutlery, the other guests having to settle for vermeil cutlery21
1855: new metals are exhibited at the Universal Exhibition in Paris. The company Pechiney is created in France.
The first industrial aluminum producer in the world moved to Salindres in the Gard, and began operating in 1860.
1876: William Frishmuth performs the first aluminum casting. In 1884, he made the cap of the Washington Monument in this metal.
1886: independently, Paul H¨¦roult and Charles Martin Hall, discover the aluminum production method by noting that it is possible to dissolve the alumina and to decompose the mixture by electrolysis (patented H¨¦roult-Hall process) to give the molten raw metal. For this discovery, Hall obtained a patent (400 655) the same year. This process makes it possible to obtain aluminum relatively inexpensively. The method developed by H¨¦roult and Hall is still used today.
1887: Karl Josef Bayer describes a method known as the Bayer process for obtaining alumina from bauxite by dissolving it with soda. This discovery brought aluminum into the era of mass production.
1888: the first aluminum production companies are founded in Switzerland, France and the United States.
From 1941 to 1959, France struck 50 c, 1 F, 2 F and 5 F aluminum coins. Previously, during the First World War and in the 1920s, very many emergency coins had already been minted in France and abroad.
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