Tin alloys are metallic materials in which tin (Sn) is the primary constituent, alloyed with elements such as copper, antimony, silver, lead, bismuth, zinc, nickel, or aluminum to enhance strength, wear resistance, corrosion behavior, melting characteristics, and reliability.
Tin alloys are essential in electronics, bearings, bronzes, coatings, and low-friction, corrosion-resistant engineering components.
Major Tin Alloy Systems
| Alloy Type | Typical Composition |
|---|---|
| Tin–Lead (Sn-Pb) | Sn 60–63%, Pb balance |
| Tin–Silver (Sn-Ag) | Sn 96–99%, Ag 1–4% |
| Tin–Copper (Sn-Cu) | Sn 97–99%, Cu 0.3–1% |
| Tin–Antimony (Sn-Sb) | Sn 85–95%, Sb 5–15% |
| Babbitt Metals | Sn + Sb + Cu |
| Bronze (Cu-Sn) | Cu 80–95%, Sn 5–20% |
| Pewter | Sn + Sb + Cu |
| Tin–Bismuth (Sn-Bi) | Sn 40–60%, Bi balance |
Chemical Composition – Generalized
| Element | Function |
|---|---|
| Tin (Sn) | Base metal – corrosion resistance & fluidity |
| Copper (Cu) | Strength & wear resistance |
| Antimony (Sb) | Hardness & creep resistance |
| Silver (Ag) | Thermal & electrical reliability |
| Lead (Pb) | Ductility & low melting point |
| Bismuth (Bi) | Low-melting alloys |
| Nickel (Ni) | Fatigue resistance |
| Zinc (Zn) | Fluidity & cost reduction |
Mechanical Properties (Typical Ranges)
| Property | Range |
|---|---|
| Tensile Strength | 30 – 450 MPa |
| Yield Strength | 15 – 300 MPa |
| Hardness | 10 – 200 HB |
| Elongation | 2 – 40% |
| Elastic Modulus | 30 – 110 GPa |
| Wear Resistance | Moderate to Excellent |
Physical Properties
| Property | Typical Range |
|---|---|
| Density | 7.3 – 9.0 g/cm³ |
| Melting Point | 140 – 300 °C |
| Electrical Conductivity | 10 – 60% IACS |
| Thermal Conductivity | 25 – 80 W/m·K |
| Corrosion Resistance | Excellent |
| Magnetic Behavior | Non-magnetic |
Strengthening & Metallurgical Behavior
Tin alloys are strengthened through solid-solution strengthening, intermetallic compound formation, grain refinement, and dispersion strengthening.
Common intermetallic phases include Cu₆Sn₅, Cu₃Sn, Ag₃Sn, and SbSn, which improve hardness, wear resistance, creep strength, and solder joint reliability.
Corrosion & Environmental Behavior
Tin alloys provide excellent resistance to atmospheric corrosion, water, and food acids. Tin acts as a sacrificial protective layer in coatings.
Limitations include exposure to strong acids, alkalis, and galvanic corrosion if improperly paired with other metals.
Refining & Processing
Primary tin is refined from cassiterite (SnO₂) via smelting and electrolytic refining. Alloying is carried out in controlled furnaces.
Tin alloys offer excellent castability, low oxidation losses, easy alloying, and good machinability, especially in antimony-bearing grades.
Available Forms
Ingots, bars, rods, wire, granules, pellets, sheets, foils, powder, pre-alloyed solder wire and paste.
Key Characteristics
✔ Low melting temperatures
✔ Excellent corrosion resistance
✔ Excellent wettability & solderability
✔ Adjustable mechanical properties
✔ Food-safe & non-toxic (lead-free grades)
✔ Superior surface finish
Applications
🔌 Electronics: lead-free solders, interconnects, plating alloys
⚙️ Bearings: Babbitt metals, low-friction components
🏭 Engineering: bronzes, marine hardware, valves
🥫 Packaging: tinplate coatings
🧪 Chemical & medical equipment
Advantages
✔ Wide property range via alloying
✔ Low energy processing
✔ Long service life
✔ Excellent joining & coating behavior
✔ RoHS & environmental compliance
Limitations
⚠ Lower strength than steel or aluminum alloys
⚠ Creep at elevated temperatures
⚠ Intermetallic brittleness if uncontrolled
⚠ Tin whisker risk in electronics
Comparison with Other Alloy Systems
| Property | Tin Alloys | Aluminum Alloys | Copper Alloys |
|---|---|---|---|
| Melting Point | Low | Medium | High |
| Corrosion Resistance | Excellent | Moderate | Excellent |
| Strength | Low–Moderate | Moderate–High | Moderate–High |
| Cost | Moderate | Low | High |
| Electrical Use | Excellent | Moderate | Excellent |
Summary:
Tin alloys combine tin’s corrosion resistance and fluidity with enhanced strength, wear
resistance, and reliability through alloying. They are indispensable in electronics,
bearings, bronzes, coatings, and corrosion-resistant engineering, offering energy-efficient
processing, design flexibility, and regulatory compliance.