We continue to review some of the most important materials in heat treatment and metallurgy.
Tin (chemical symbol: Sn)
Tin (Fig. 1) is a silvery-white, soft, malleable metal that can be polished to a lustrous shine. Its microstructure is highly crystalline. When a bar of the element is bent, a distinct noise known as a “tin cry” can be heard, which is caused by the breaking of its crystals. Chemically, tin has similarities to both its neighbors on the periodic table – germanium and lead. Tin is the 49th-most abundant element and has the largest number of stable isotopes (10) of any element. It comprises about 0.001% of the earth’s crust.
Tin has been used on the large scale since ancient times (3000 BC) in combination with copper to make bronze, but it wasn’t available in its pure metallic form until some 1,400 years later. In more modern times, the invention of the tin can (Fig. 2) in 1810 by British merchant Peter Durand was quintessential for the ability to can/preserve food. The tin can found great success during the Civil War as military leaders looked for ways to preserve food and feed their soldiers. Interestingly enough, what we call a “tin” can is actually made out of steel that has been coated with tin to prevent rusting. While the tin can may not be as abundant as it once was, tin still manages to find its way into a number of applications.
Tin is very soft and malleable and thus can be rolled, pressed or hammered into very thin sheets (tin foil). In addition, elemental tin resists distilled, sea and soft tap water but is attacked by strong acids, alkalis and acid salts. Oxygen in solution accelerates the attack.
Tin is corrosion-resistant and is therefore often used in protective coatings of other metals using the process of electroplating, which is one of its most widely used applications. These tinned pieces can have a number of applications, including kitchen utensils, spray components, shaving foam, ink cans, electronic parts, circuit boards, clips and pins. Furthermore, tin has other uses for the creation of window glass using the Pilkington process in which molten glass is poured atop a pool of molten tin. The glass floats on the surface of the tin and cools, forming solid glass with flat, parallel surfaces.
Pure tin has many applications, such as in the production of electronic valves, food packaging for beverages, the construction of storage tanks for pharmaceutical chemicals, capacitor electrodes, fuse wires and for ammunition.
Here are a few important facts about tin.
- Atomic number: 50
- Atomic weight: 118.710
- Melting point: 505.08 K (231.93°C or 449.47°F)
- Boiling point: 2875 K (2602°C or 4715°F)
- Density: 7.287 grams per cubic centimeter
- Phase at room temperature: Solid
- Element classification: Metal
- Period number: 5
- Group number: 14
- Group name: Post-transition metals