Element of Aluminum

Element of Aluminum

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Aluminum is a chemical element, with the chemical symbol is Al, and a relative density of 2.70. It is a soft and malleable silver-white metal, and the third most abundant element in the earth’s crust (after oxygen and silicon), accounting for about 8% of the mass of the solid surface of the earth.

Aluminum is valued for its low density and corrosion resistance. Structural parts made of aluminum and its alloys are not only critical in the aerospace industry, but also in the fields of transportation and structural materials.

Physical Properties

Aluminum is a light metal, and only possesses one-third that of iron. Pure aluminum is soft, losing its tensile strength at around 300°C, with a melting point of 660.4°C. Through processing aluminum into aluminum alloy, it allows them to be tougher and more ductile, when the toughness of pure aluminum is 7~11MPa, and aluminum alloy reaches 200-600MPa.

Through metallic luster, the surface is silvery and shiny when smooth, and dark gray when rough, which has the characteristic of non-magnetic and difficult to ignite, strong ability to reflect visible light (~ 92%), easy to process, cut, and shape. It also has good electrical and thermal conductivity (59% of copper), which is far lighter than copper.

Chemical Properties

Aluminum reacts with oxygen extremely easily, and when exposed to air, dense aluminum oxide will form on its surface (this process is passivation), which effectively prevents its continued oxidation, displaying a silver-gray color.

The aluminum products we usually see have been oxidized. And its oxide film makes aluminum difficult to corrode.

At a temperature of 280 °C, aluminum will begin to oxidize by water, generating hydrogen and aluminum hydroxide and heat.

Different from ordinary metals, aluminum can react with acids and strong bases. Therefore, aluminum is considered to be an amphoteric metal, which aluminum oxide is called amphoteric oxide, and aluminum hydroxide is called amphoteric.

Under room temperature, aluminum would not react when it’s passivated in concentrated nitric acid and concentrated sulfuric acid, therefore, concentrated nitric acid residue will be left in aluminum cans (which can last about 180 hours).

Source: Wikipedia

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