What is Tin? – Its Alloys, Properties, and Uses

What is Tin?

Tin (Sn) is a chemical element in the periodic table’s Group 14 (IVa) carbon family’s carbon family. Tin is a silvery-white, soft metal that is light and easy to melt.

That was known to the ancients as bronze, a copper alloy. Tin is commonly utilized in the plating steel cans used as food containers, bearing metals, and solder.

Tin is rarely used as a pure metal due to its softness; instead, it is mixed with other metals to create alloys with many good tin qualities. These qualities include minimal toxicity and strong corrosion resistance. 

Tin is highly crystalline, malleable, and ductile. When a tin bar is bent, a distinctive cracking sound called the “tin cry” is created due to crystal breaking.

Strong acids, alkalis, and acid salts do not corrode the metal, but it is vulnerable to distilled water, ocean, and soft tap water. When oxygen is present in the solution, it functions as a catalyst, speeding up the chemical assault.

History of Tin

Tin is one of the oldest metals known, and it has long been utilized as a component of bronze. Tin was utilized in bronze utensils as early as 3500 B.C.E. Its hardening effect on copper.

Tin mining is thought to have begun in classical times in Cornwall and Devon (particularly Dartmoor). A lively tin trade developed with civilizations of the time; with the civilizations of the Mediterranean, rich in commerce emerged. 

However, pure metal was not used until around 600 B.C.E. At South Crofty near Camborne, the last Cornish tin mine closed in 1998, bringing the county’s mining history to a halt after four thousand years. Many Germanic and Celtic languages have cognates for the word “tin.”

According to the American Heritage Dictionary, the word was derived from a pre-Indo-European language. In modern times, the term “tin” is frequently used to describe any silvery metal in thin sheets. 

Most generally referred to as tin items, such as aluminum foil, beer cans, and tin cans, are made of steel or aluminum.

However, tin cans do have a thin tin coating to prevent rust. Similarly, so-called “tin toys” are frequently composed of steel, with or without a thin tin coating to prevent rust.

Manufacturing Process of Tin

1. Ore Concentration

Gravel pumping is used to extract the majority of tin ore. This procedure involves removing the barren overburden with draglines or shovels, then breaking up and dislodging the tin-bearing sand with high-pressure water jets.

The slurry of mud and water is then sucked up by a submerged gravel pump and raised to a series of sluice boxes, or palongs, that slope downhill and have baffles spaced along their length. 

The heavier minerals, such as cassiterite, sink to the bottom of the slurry as it moves along, while the lighter waste material pours over the boxes’ ends to tailings dumps. The crude concentrate is periodically extracted, and the flow is stopped.

Gravity separation procedures such as jigs and shaking tables concentrate ore. The concentrate is then collected and taken ashore for further processing while the barren material is discharged over the dredge’s stern. Tin metal makes around 70 to 75 percent of concentrates sent to the smelter.

2. Smelting

Low-grade concentrates from complex ores are first roasted to remove sulfur at temperatures between 550 and 650 °C in a reverberatory or multiple-hearth furnace before being smelted.

Oxidizing, reducing, or chlorinating reactions occur depending on the kind and quantity of impurities. To eliminate contaminants produced soluble by roasting, leaching with water or acid solutions is commonly used.

The furnace feed for smelting contains tin oxide and impurities, such as iron oxides, that were not eliminated during mineral processing or roasting.

Reverberatory furnaces, blast furnaces, and electric furnaces are the three types of tin smelting furnaces. Typically, the operation is completed in batches.

The impure tin is tapped off and cast into big slabs at the end of the smelting process, while the slag is hardened into granules by being put into water tanks.

The granulated slag, which may still contain some tin, is withdrawn, while the impure tin slabs are refined further.

3. Refining

Impure tin can be refined in one of two ways. The most prevalent method is fire refining, which yields tin appropriate for normal commercial use (up to 99.85 percent). Electrolytic refining is utilized on the products of complex ores to generate a very high-quality tin (up to 99.999 percent).

Boiling is a fire-refining technique. Impure tin from the smelter or tin from the liquidation furnace is heated in vessels or kettles agitated by compressed air in this process. The result is that the impurities oxidize and rise to the surface, forming dross.

Liquation is another method to refine fire. It eliminates impurities with a higher melting temperature than tin from impure tin and dross from smelting. In a reverberatory furnace, the materials are put on a sloping hearth and heated to just above the melting point of tin.

The tin slowly melts and runs down the slope, collecting in a receptacle while the unmelted dregs remain on the hearth. After that, these are removed and treated.

Impure tin is cast into anodes during electrolytic refining, and Starting cathodes constructed of thin sheets cast from high-purity tin are placed in an acidic electrolyte.

Certain agents are necessary for the electrolyte to obtain dense, compact cathode deposits. The cathodes are removed after approximately a week. Tin is typically marketed in ingots or pigs, made from refined tin.

Alloys of Tin

1. Bronze

Bronze was the first tin alloy utilized significantly, dating back to 3000 BC (The beginning of the Bronze Age). Bronze is a copper-based alloy with about 12–12.5% tin, other metals (such as aluminum, manganese, nickel, or zinc), and nonmetals or metalloids (such as arsenic, phosphorus, or silicon). 

These additions result in a variety of alloys that are harder than copper or have different qualities like stiffness, ductility, or machinability.

Higher tin bronzes cast church bells and concert bells (carillons). In addition to their ornamental value, they have useful features such as permanence and good sound quality.

2. Solder

There are various older alloy compositions, but the most important are the tin-lead solders employed by the Romans and are still used today. Tin melts at 232°C, while lead melts at 327°C. The eutectic is the name given to this mixture.

Soldiers used in the industrial and electronic industries account for a large tin usage. Tin, as well as other metals, including antimony (Sb), bismuth (Bi), silver (Ag), and copper, are used in lead-free solders (Cu).

3. Babbitt Metal or Bearing Metals

Tin has a low friction coefficient. It is the most important factor to consider while making bearings. Tin is a fundamentally weak metal.

Hence it is alloyed with copper and antimony in bearing applications to boost hardness, tensile strength, and fatigue resistance.

4. Pewter

Pewter is a malleable metal alloy made up of 85-95 percent tin, with the rest being copper, antimony, bismuth, and, less frequently, lead. Silver is also used on occasion. Lead is abundant in the lowest grades of pewter, which have a bluish tint, and copper and antimony act as hardeners. 

Depending on the alloy, its melting point ranges from 338 to 446 degrees Fahrenheit (170 to 230 degrees Celsius). Pewter takes advantage of the beauty and convenience of working with tin while adding other metals for robustness.

Compounds of Tin

1. Tin Halides

All four tetrahalides of tin have been identified. All of these halides, except for SnF4, are generated by covalent bonding with volatiles found in nature. SnF4 is a hygroscopic white solid that forms when SnCl4 is treated with anhydrous HF.

The other SnX4 compounds are better formed by joining metal and halide directly. Colorless liquids SnCl4 and SnBr4 exist alongside a brilliant orange solid SnI4.

Sn is more stable in its divalent state than in its tetravalent state. As a result, Sn produces all stable dihalides. Because of the poisonous nature of Sn, the dihalide SnF2 has been replaced by NaF in toothpaste.

2. Tin hydride

Group-14 elements all form gaseous hydrides like MH4. From Ge to Pb, the stability of group-14 hydrides drops rapidly. At room temperature, SnH4 decomposes slowly and is unaffected by dilute aqueous acids and alkalis.

Concentrated acids or alkalis, on the other hand, destroy it. Inorganic chemistry, SnH4 is a useful reducing agent. It’s utilized to turn benzaldehyde into benzyl alcohol and nitrobenzene into aniline.

3. Tin Oxide

Tin is typically found in nature as cassiterite or tinstone (SnO₂). It’s a solid white color that’s amphoteric. The reaction of Sn with fused NaOH and concentrated H₂SO4 demonstrates its amphoteric character.

SnO₂ + 2NaOH + H₂O → Na₂Sn (OH)₆

SnO₂ + 2H₂SO₄ → Sn (SO₄)₂ + 2H₂O

Sn can also form a stable divalent oxide with the chemical formula SnO. It has higher basicity than SnO₂. In the absence of air, stannous oxalate is thermally decomposed to produce SnO.

SnC₂O4 → SnO + CO + CO₂

Properties of Tin:

• It is a soft and pliable metal with a bluish-white color and an atomic number of 50.
• The tin comes in two main forms (or allotropes): white and grey.
• At room temperature, oxygen and water do not affect the tin. It is also corrosion-resistant. It is utilized as a coating for other metals because of this.
• Tin makes up about two parts per million of the earth’s crust.
• This element is found in igneous rocks of the earth’s crust at a concentration of about 0.001%, making it scarce rather than rare.
• It is abundantly found alongside other elements such as cobalt, copper, nickel, cerium, and lead.
• When reacting with water and oxygen at higher temperatures, the metal forms its oxide.
• At temperatures above 13.2 °C and very quickly above 100 °C, the grey metal changes color to white. This metal comes in roughly ten distinct isotopes, each with a different mass number.

Uses of Tin

• Tin was an essential metal in prehistoric civilizations. It’s mostly utilized on food packaging as a non-toxic corrosion-resistant coating.
• It can combine with other elements to make various alloys. Pewter, for example, has 90–95 percent Sn, 1–8% Sb, and 0.5–3% Cu. Trays, plates, and trophies are all made from it. Organ pipes are 90 to 95 percent Sn and Pb alloy.
• Tin and lead are combined to make solder, mostly used to join pipes and electrical circuits.
• Tin is used to prevent corrosion in lead, zinc, and steel. Food preservation is commonly done in tin-plated steel containers. Roofing and gasoline tanks are sheet steel covered with a Pb-Sn alloy.
• Tin is sometimes used in the production of American and Canadian coins. Copper is the most common element in these coins.
• Coils are made from niobium-tin compounds. Because of their high critical temperature, these coils are utilized to make superconducting magnets.

Advantages of Tin

• Tin is a soft, ductile, and malleable silver-white metal. Tin can be molded and stretched into various shapes without splitting because of its elasticity.
• Tin is also regarded as non-toxic, conductive, and corrosion-resistant.

Disadvantages of Tin

• Organic tin is the most hazardous to one’s health. It can produce serious side effects in humans, such as eye and skin irritations, headaches, nausea, dizziness, breathlessness, extreme perspiration, and urinary difficulties.
• The metal is not biodegradable, which is the biggest disadvantage. As a result, there may be an effect on the environment.

Conclusion

Tin is a fundamental chemical element. It is most typically utilized as a plating on steel sheets to make food cans.

Tin is also used to make bronze and solder when mixed with copper. Tin is mostly used to provide non-toxic corrosion-resistant coatings for steel, particularly for food packaging.

FAQs

References:

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