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

What is Tin?

Tin (Sn), a member of Group 14 in the periodic table, belongs to the carbon family. It stands out as a silvery-white metal that is both soft and easily melted, characteristics that have long made it useful for various applications.

Historically, tin has played a crucial role, particularly in the production of bronze—a well-known alloy of copper and tin that dates back to ancient times. In modern use, tin often appears as a protective coating on steel cans for food storage, as well as in bearing metals and solder.

Pure tin is seldom used on its own because of its softness. Instead, it is usually combined with other metals to form alloys that take advantage of tin’s beneficial properties, such as its low toxicity and excellent resistance to corrosion.

Structurally, tin is highly crystalline, malleable, and ductile. One of its interesting features is the “tin cry,” a crackling sound that occurs when a bar of tin is bent—caused by the breaking of its crystals.

Chemically, tin holds up well against strong acids, alkalis, and acid salts, showing little tendency to corrode. However, it is more vulnerable to distilled water, seawater, and even soft tap water. In these environments, the presence of oxygen acts as a catalyst, accelerating the rate at which tin undergoes chemical attack.

History of Tin

Tin stands among the earliest metals known to humanity, valued for its crucial role in forming bronze. Evidence shows that as far back as 3500 B.C.E., tin was already being combined with copper to make bronze utensils, a practice that capitalized on tin’s ability to harden copper.

The history of tin mining in Britain stretches back to classical antiquity, especially in regions like Cornwall and Devon—Dartmoor being particularly notable. From these areas, a robust trade in tin flourished, linking local communities to Mediterranean civilizations and fueling commercial growth across the region.

Interestingly, it wasn’t until around 600 B.C.E. that people began using pure tin metal itself. Fast-forward to recent history, the last chapter of Cornwall’s tin mining legacy closed in 1998, when South Crofty mine near Camborne ceased operations, ending nearly four thousand years of continuous mining.

Linguistically, the word “tin” has a long lineage as well. Variants appear in many Germanic and Celtic languages, and according to the American Heritage Dictionary, its origins can be traced to a pre-Indo-European language.

In contemporary usage, “tin” has become something of a catch-all for any silvery metal fashioned into thin sheets. Ironically, many everyday items referred to as “tin” such as aluminum foil, beer cans, and “tin cans” are actually made from steel or aluminum.

Yet, genuine tin cans do incorporate a thin layer of tin to prevent rusting. Likewise, the so-called “tin toys” of the past were usually constructed from steel, sometimes coated with tin to ward off corrosion.

Manufacturing Process of Tin

1. Ore Concentration

Most tin ore is extracted using a method known as gravel pumping. In this process, the initial step is to clear away the unproductive overburden, typically with draglines or shovels. Once this layer is removed, high-pressure water jets are used to break up and loosen the tin-bearing sand beneath.

The resulting mixture of water and mud forms a slurry, which is drawn up by a gravel pump located underwater. This slurry is then directed into a series of sluice boxes, sometimes called palongs, which are set on a slope and fitted with baffles at intervals along their length.

As the slurry moves through these boxes, heavier minerals like cassiterite settle to the bottom, while lighter waste material is washed away over the ends, eventually collecting in tailings dumps. Operators periodically halt the flow to remove the accumulated concentrate.

Subsequent concentration of the ore is achieved through gravity separation techniques, such as using jigs and shaking tables. The resulting concentrate is collected and transported ashore for further refinement, while the waste material is simply discharged from the back of the dredge. Typically, the concentrate shipped to the smelter contains about 70 to 75 percent tin metal.

2. Smelting

When dealing with low-grade concentrates derived from complex ores, the material is first subjected to roasting at temperatures ranging from 550 to 650 °C. This process, often carried out in either a reverberatory or multiple-hearth furnace, is primarily intended to drive off sulfur before smelting begins.

Depending on the specific impurities present both in type and quantity, the system may undergo oxidizing, reducing, or chlorinating reactions during treatment. To address contaminants that become soluble as a result of roasting, it is common practice to apply leaching, either with water or acid solutions, to wash them away.

As for the smelting feed itself, it generally comprises tin oxide alongside various impurities—iron oxides among them—that remain after earlier stages of mineral processing or roasting. Smelting is conducted using one of three furnace types: reverberatory, blast, or electric. Typically, these operations are carried out in discrete batches rather than as a continuous process.

At the conclusion of smelting, the impure tin is tapped from the furnace and cast into large slabs. Meanwhile, the slag is rapidly cooled and solidified by immersing it in water tanks, forming granules. After this, the granulated slag, which may still trap small amounts of tin, is separated, and the crude tin slabs are sent on for further refining.

3. Refining

Tin purification is typically accomplished by two main methods. The most widely used approach is fire refining, which produces tin suitable for general commercial applications, achieving a purity of up to 99.85 percent.

For situations where exceptionally pure tin is required, such as when dealing with complex ores, electrolytic refining is employed, and this method can yield tin of remarkable purity, reaching up to 99.999 percent.

One of the classic fire-refining techniques is boiling. In this process, impure tin, whether straight from the smelter or the liquidation furnace, is heated in large vessels or kettles. Compressed air is introduced to agitate the molten metal, which encourages impurities to oxidize. These oxidized impurities then rise to the surface, forming a layer of dross that can be skimmed off.

Another fire-refining technique, known as liquation, is particularly effective for removing impurities with higher melting points than tin itself. Here, the impure tin, often mixed with dross from smelting, is placed on a sloping hearth inside a reverberatory furnace and gently heated to just above the melting point of tin.

As the tin melts, it flows down the slope and collects in a separate container, while any unmelted residue is left behind on the hearth. These remaining dregs are then collected and processed further.

When a higher grade of purity is needed, electrolytic refining comes into play. In this method, impure tin is cast into anodes, while the starting cathodes are thin sheets made from high-purity tin.

Both are submerged in an acidic electrolyte, and specific agents are added to ensure that tin deposits on the cathode are dense and compact. After about a week in the electrolyte bath, the cathodes are removed, now bearing deposits of highly refined tin.

Finally, the refined tin is typically cast into ingots or pigs, ready for commercial distribution.

Alloys of Tin

1. Bronze

Bronze stands out as the earliest tin alloy to be widely adopted, with its use tracing back as far as 3000 BC, marking the onset of the Bronze Age. Essentially, bronze is a copper alloy that typically contains about 12 to 12.5% tin.

Alongside tin, other metals, including aluminum, manganese, nickel, and zinc, may be present, as well as certain nonmetals or metalloids like arsenic, phosphorus, or silicon.

By incorporating these additional elements, various bronze alloys emerge, each offering properties superior to pure copper. These can include increased hardness, enhanced stiffness, improved ductility, or better machinability, depending on the specific combination.

When it comes to applications, bronzes with a higher tin content are traditionally chosen for casting church bells and carillons (concert bells). Besides their decorative appeal, these bells are valued for their durability and the rich, resonant sound they produce, qualities that have made them a staple in both religious and musical settings.

2. Solder

Over the centuries, a variety of alloy compositions have been developed, but among the most significant are the tin-lead solders first used by the Romans; remarkably, these are still in use today. Tin, with a melting point of 232°C, and lead, which melts at 327°C, combine to form what is known as an eutectic mixture.

In both industrial and electronic sectors, solder represents a major application of tin. Beyond tin itself, modern lead-free solders may incorporate other metals such as antimony (Sb), bismuth (Bi), silver (Ag), and copper (Cu), reflecting a shift in material choices as technology and safety standards evolve.

3. Babbitt Metal or Bearing Metals

Tin is notable for its low coefficient of friction, which is a crucial property when designing bearings. On its own, however, tin is a relatively weak metal. For this reason, it is commonly alloyed with copper and antimony in bearing applications.

The addition of these elements significantly enhances tin’s hardness, tensile strength, and resistance to fatigue, making it more suitable for use in demanding mechanical environments.

4. Pewter

Pewter is a flexible metal alloy, primarily composed of tin typically ranging between 85 and 95 percent. The remainder usually consists of metals like copper, antimony, and bismuth, and, in some cases, lead.

Occasionally, silver is also included. Lower-quality pewter contains higher amounts of lead, which gives it a subtle bluish hue, while both copper and antimony are added to increase the metal’s strength.

The melting point of pewter depends on the specific blend of metals, but it generally falls somewhere between 338 and 446 degrees Fahrenheit (170 to 230 degrees Celsius). This alloy combines the attractive appearance and easy workability of tin with the durability provided by its other components, making pewter both appealing and practical for a variety of uses.

Compounds of Tin

1. Tin Halides

All four tetrahalides of tin have been identified in chemical research. Interestingly, with the exception of tin(IV) fluoride (SnF₄), these tetrahalides are typically formed through covalent interactions with naturally occurring volatile halogen compounds. SnF₄ itself is a hygroscopic white solid, most commonly synthesized by reacting tin(IV) chloride (SnCl₄) with anhydrous hydrogen fluoride.

For the remaining tin tetrahalides namely SnCl₄, SnBr₄, and SnI₄ a more effective method of preparation involves the direct combination of tin metal with the respective halogen. Both SnCl₄ and SnBr₄ are colorless liquids under standard conditions, whereas SnI₄ stands out as a striking orange solid.

It is also worth noting that tin tends to be more stable in its +2 oxidation state compared to the +4 state. This preference means that tin forms a complete series of stable dihalides. However, due to concerns over toxicity, tin(II) fluoride (SnF₂) is no longer used in toothpaste formulations; sodium fluoride (NaF) has taken its place as a safer alternative.

2. Tin hydride

The elements of Group 14 are known to form gaseous hydrides of the general formula MH₄. However, as we move from germanium down to lead, there is a noticeable and rapid decline in the stability of these hydrides.

For example, stannane (SnH₄) is only moderately stable at room temperature; it tends to decompose slowly under these conditions and does not react with dilute aqueous acids or bases.

In contrast, when exposed to concentrated acids or alkalis, SnH₄ is readily broken down. Within the context of inorganic chemistry, stannane serves as a practical reducing agent. It finds use in specific transformations, such as converting benzaldehyde to benzyl alcohol and reducing nitrobenzene to aniline.

3. Tin Oxide

Tin most commonly occurs in nature as cassiterite, also known as tinstone (SnO₂). This compound appears as a solid white substance and is classified as amphoteric. You can see this amphoteric nature in action through its reactions with both fused sodium hydroxide and concentrated sulfuric acid:

When SnO₂ reacts with sodium hydroxide and water, the result is sodium hexahydroxostannate:

SnO₂ + 2NaOH + H₂O → Na₂Sn(OH)₆

On the other hand, if you treat SnO₂ with concentrated sulfuric acid, you get stannic sulfate and water:

SnO₂ + 2H₂SO₄ → Sn(SO₄)₂ + 2H₂O

In addition to this, tin can also form a stable oxide in the +2 oxidation state—SnO—which is notably more basic than SnO₂. If you heat stannous oxalate (SnC₂O₄) in the absence of air, it breaks down to produce SnO along with carbon monoxide and carbon dioxide:

SnC₂O₄ → SnO + CO + CO₂

Properties of Tin:

• Tin is a soft, easily shaped metal distinguished by its bluish-white hue and holds the atomic number 50.
• This element exists primarily in two forms white tin and grey tin each with its own characteristics.
• At standard room temperature, tin remains unaffected by both oxygen and water, which contributes to its notable resistance to corrosion. This property makes it especially valuable as a protective coating for other metals.
• In terms of abundance, tin constitutes approximately two parts per million of the Earth’s crust.
• Within igneous rocks, tin appears at about 0.001% concentration. This low presence means tin is scarce, but not considered extremely rare.
• Tin is often discovered in nature alongside elements like cobalt, copper, nickel, cerium, and lead.
• When tin reacts with water and oxygen at elevated temperatures, it forms an oxide layer on its surface.
• If the temperature rises above 13.2 °C, and especially when it exceeds 100 °C, grey tin gradually transforms into its white form. Additionally, tin has around ten different isotopes, each varying in mass number.

Uses of Tin

• Tin played a vital role in the earliest human societies, valued for its unique properties. Today, you’ll often find it used as a non-toxic, corrosion-resistant coating on food packaging, helping to ensure both safety and longevity.
• One of tin’s distinguishing features is its ability to form useful alloys with other elements. Take pewter, for instance: typically composed of 90–95% tin, with small amounts of antimony (1–8%) and copper (0.5–3%). This alloy has a long history of being crafted into trays, plates, and trophies. Interestingly, organ pipes are made from an alloy of tin and lead, usually with a similar proportion of tin around 90 to 95%.
• The combination of tin and lead is especially significant in the production of solder. Solder is indispensable for joining pipes and assembling electrical circuits, thanks to its reliable melting point and adhesive qualities.
• Tin’s effectiveness in preventing corrosion makes it a staple in protecting metals such as lead, zinc, and steel. You might notice, for example, that many food containers are made from tin-plated steel an approach that extends their shelf life. In construction and industry, sheet steel coated with a lead-tin alloy is widely used for roofing and gasoline tanks.
• Tin occasionally appears in the manufacture of coins in countries like the United States and Canada, although copper remains the primary metal in most of these coins.
• Finally, when it comes to advanced technology, tin forms compounds with niobium to produce coils. These niobium-tin coils are essential for creating superconducting magnets, thanks to their high critical temperature.

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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