Tin is a silvery-white metal identified by the chemical symbol Sn, derived from the Latin word stannum. It is soft, malleable, and notably non-toxic, melting at a relatively low temperature of 231.9 °C (449.4 °F). Tin resists corrosion effectively because it naturally forms a thin, invisible layer of stannic oxide when exposed to air. This layer shields the underlying metal from further reaction. These fundamental properties allow tin to be incorporated into a wide variety of daily products, primarily through mixing it with other metals or using it as a specialized coating.
Tin in Common Metallic Mixtures
The most widespread use of tin is in the creation of alloys, where it is chemically bonded with other metals to achieve specific performance characteristics.
Bronze
One of the oldest and most historically significant tin alloys is bronze, which is primarily a mixture of copper and tin. Traditionally, bronze contains about 12.5% tin. The addition of tin strengthens the copper, lowers its melting point, and increases its resistance to corrosion. This combination of traits defined the Bronze Age.
Solder
Tin is a fundamental component of modern solder, which is used to join metal workpieces and electrical components. While older solders were a mixture of tin and lead, modern electronics often require lead-free solders. These contain a higher percentage of tin, typically alloyed with metals like silver or copper, benefiting from the element’s low melting point.
Pewter
Pewter consists of tin as the main ingredient, making up between 85% and 99% of the mixture. Modern, food-safe pewter is typically hardened with small amounts of copper and antimony. It is used to create decorative items, figurines, and tableware, benefiting from tin’s characteristic sheen and malleability.
Use in Protective Coatings
The non-toxic nature and excellent corrosion resistance of tin make it an ideal material for coating or plating other metals. The familiar “tin can” is not pure tin but is tinplate, a thin sheet of steel coated with a fine layer of tin, often applied through electroplating. The tin coating acts as a physical barrier, preventing the iron in the steel from oxidizing and rusting. For food packaging, the tin layer prevents the contents from reacting with the steel, helping to preserve flavor and nutritional value. Tin plating is also extensively used on electrical connectors and wiring, where it protects copper from oxidation and ensures the contact remains clean and conductive.
Unique Industrial and Chemical Applications
Beyond its metallic uses in alloys and plating, tin plays a role in various industrial processes and chemical compounds.
Float Glass Manufacturing
A substantial amount of tin is utilized in the manufacturing of flat glass through the float glass process. In this method, molten glass is poured onto a large bed of molten tin. The tin remains perfectly flat due to its high density and relative chemical inertness. The glass floats on the surface and spreads out evenly as it cools, resulting in the smooth, uniform sheets used for windows and mirrors.
Chemical Compounds
Tin is a precursor for specialized chemical compounds, such as organotin compounds, which contain a tin-carbon bond. These compounds are used as stabilizers in the production of rigid polyvinyl chloride (PVC) plastics. They prevent the plastic from degrading when exposed to heat or ultraviolet light. Tin oxides are also employed in the ceramics industry as opacifiers and in the electronics sector to create transparent, electrically conductive coatings on glass for applications like touchscreens and solar panels.