Tin

TIN

Tin (chemical symbol Sn) is produced from the ore containing the mineral cassiterite, which is a tin oxide. Since there is little cassiterite in North America, tin has to be imported from Malaysia, Brazil, Russia, Indonesia, Thailand, China and Bolivia. The ore usually contains little tin, so an extensive refining process is required.

Properties of Tin

Tin is soft metal that is malleable and ductile and blue-white in color. It is corrosion resistant when exposed to air and moisture. It will take a high polish and has properties enabling it to coat other metals.

Work Characteristics

Because tin is soft and malleable, it can be worked by rolling, spinning, extrusion and casting.

Production of Tin

After the ore is mined the impurities must be removed to get a concentrated ore. This involves a series of mechanical and chemical processes for crushing and cleaning the ore. Magnetic separators and screening operations are used from which the ore and the tailings are separated.

The concentrated cassiterite is refined, producing a high-purity metal of at least 99.8 percent tin. Several different processes are used but they all involve smelting (melting) the ore in a furnace in which a crude tin is separated from the slag. The crude tin is then heated to a predetermined temperature at which impurities with higher melting temperatures than tin remain. This process is called liquidation. This partly pure tin is drawn off and heated above its boiling point. As it is stirred, additional impurities rise to the surface and are drawn off. This continues until impurities are removed, leaving an almost pure tin.

Uses of Tin

Since tin and tin alloys have high corrosion resistance and excellent coating ability, they are used extensively to provide protective coatings on other metals, especially steel. One example is a coating on cans used to store food for retail sale. Tin is also used as an alloying element in other metals. Its low melting point makes it useful in some solders. It finds applications in mirrors, hardware and fusible alloys. Tin compounds are used in the production of glazed, glass and porcelain enamel