Grade C Tin is a commercial-purity refined tin containing a minimum of 99.90% tin (Sn). It occupies the middle ground between ultra-high-purity electronic grades and industrial alloying grades, making it suitable for general manufacturing, tinplate production, solder alloys, and chemical applications where extreme purity is not required.
Basic Identification
| Property | Value |
|---|---|
| Purity | ≥ 99.90% Sn |
| Allotropic Form | β-Tin (White Tin) |
| Crystal Structure | Body-Centered Tetragonal (BCT) |
| Common Standards | ASTM B339, ISO 21948, EN 610, JIS H2108 |
Mechanical Properties
| Property | Typical Value |
|---|---|
| Tensile Strength | 15 – 25 MPa |
| Yield Strength | Very low |
| Elongation | 30 – 40% |
| Hardness | ~6 – 10 HV |
| Ductility | Very good |
| Creep Resistance | Low |
Physical Properties
| Property | Value |
|---|---|
| Density | 7.31 g/cm³ |
| Melting Point | 231.9 °C |
| Electrical Conductivity | ~14 – 15% IACS |
| Thermal Conductivity | ~65 W/m·K |
| Magnetic Behavior | Diamagnetic |
| Appearance | Silvery-white metallic |
Strengthening & Metallurgical Behavior
Grade C Tin is not heat-treatable. Strengthening is limited to solid-solution effects from trace impurities and minor work hardening during processing.
Compared to ultra-high-purity tin, Grade C Tin exhibits improved dimensional stability and a slightly lower risk of tin whisker formation, while still remaining unsuitable for structural load-bearing applications.
Key Characteristics
✔ Good balance of purity and cost
✔ Excellent castability and formability
✔ Good solderability
✔ Lower whisker risk than 99.99% tin
✔ Widely available globally
❌ Not suitable for high-reliability microelectronics
Refining & Processing
Grade C Tin is produced via tin ore concentration, smelting, fire refining, and optional limited electrolytic refining. Full electrolytic refining is not always applied, which keeps production costs lower than Grade A or electronic-grade tin.
| Processing Property | Behavior |
|---|---|
| Castability | Excellent |
| Rolling | Very good |
| Machining | Poor (soft metal) |
| Solder Compatibility | Good |
| Electroplating Use | Limited |
Available Forms
Tin ingots / pigs
Tin bars
Granules and shots
Tin wire
Alloy feedstock
Applications
🏭 Tinplate production and general manufacturing
⚙️ Bronze, Babbitt, and solder alloying
⚡ General-purpose electrical solders and coatings
🧪 Chemical intermediates and float glass bath replenishment
🔩 Foundry and master alloy production
Advantages
✔ Cost-effective compared to higher purity grades
✔ Versatile for industrial use
✔ Easy melting, casting, and forming
✔ Stable global supply
Limitations
❌ Not suitable for aerospace or defense electronics
❌ Impurities may affect long-term electrical reliability
❌ Reduced corrosion resistance in aggressive environments
Grade C Tin vs Grade A Tin
| Feature | Grade C (99.90%) | Grade A (99.99%) |
|---|---|---|
| Purity | High | Ultra-high |
| Cost | Lower | Higher |
| Whisker Risk | Lower | Higher |
| Electronics Use | General | Critical |
| Alloying Use | Excellent | Excellent |
Why Choose Grade C Tin?
Grade C Tin (99.90%) is selected when cost efficiency and industrial versatility are more important than ultra-high purity. It delivers reliable performance for alloying, coating, tinplate, and general manufacturing at an economical price point.