DESCRIPTION
Tin (from Latin stannum) is a chemical element, with symbol Sn and atomic number Z=50. The most important tin ore is cassiterite, SnO2. There are no known high-grade deposits of this mineral. Most of the world’s tin ore is obtained from low-grade alluvial deposits. There are two allotropic forms of tin: white tin and gray tin.
Tin is obtained from cassiterite, where it occurs as tin dioxide. This ore is ground and enriched in tin dioxide by flotation, then roasted and heated with coke in a reverberatory furnace to obtain the metal by carbothermal reduction.
PROPERTIES
It melts at low temperature; it has great fluidity when molten and has a high boiling point; it is also highly resistant to corrosion in many media. Tin reacts with both strong acids and strong bases, but is relatively resistant to near neutral solutions. Normally when subjected to a corrosion process, no hydrogen gas is released from the tin and the corrosion rate is governed by the supply of oxygen or other oxidizing agents; in its absence, corrosion is negligible. A thin oxide film forms on tin that is exposed to air and this gives rise to surface protection. Salts that react acidically in solution, such as aluminum chloride and ferric chloride, attack tin in the presence of oxidants or air. Most non-aqueous liquids, such as oils, alcohols or chlorinated hydrocarbons, have no significant effect on tin. Tin and simple inorganic salts are non-toxic, but some forms of organotin compounds are toxic.
Tin metal is not classified as a hazardous substance by the EU or as dangerous goods for transport.
APPLICATIONS
- Protective coatings against corrosion.
- Manufacture of bronzes.
- Soft soldering.
- Manufacture of ceramic enamels.
