Blister Tin is crude, partially refined tin metal produced immediately after the primary smelting of tin ore (cassiterite – SnO₂).
It is called “blister” because its surface often shows gas bubbles and blisters caused by entrapped impurities and gases during solidification.
Note: Blister tin is an intermediate metallurgical product and is not suitable for direct industrial or commercial use without further refining.
Basic Information
| Property | Value |
|---|---|
| Chemical Symbol | Sn |
| Metallurgical State | Crude / Intermediate Metal |
| Typical Purity | 96 – 99 % Sn |
| Allotrope | β-Tin (White Tin) |
| Industrial Use | Refining feedstock only |
Chemical Composition (Typical)
| Element | Content (%) |
|---|---|
| Tin (Sn) | 96 – 99 |
| Iron (Fe) | 0.1 – 1.0 |
| Copper (Cu) | 0.05 – 0.5 |
| Lead (Pb) | 0.05 – 0.5 |
| Arsenic (As) | Trace – 0.3 |
| Antimony (Sb) | Trace – 0.3 |
| Sulfur / Oxygen | Residual |
Composition varies widely depending on ore source, smelting method, and furnace control.
Mechanical Behavior
| Property | Behavior |
|---|---|
| Tensile Strength | Low & inconsistent |
| Ductility | Poor |
| Hardness | Higher than refined tin (impurity-driven) |
| Fracture Mode | Brittle / intergranular |
| Structural Use | ❌ Not suitable |
Blister tin is not characterized for mechanical performance due to impurity-driven behavior.
Physical Properties
| Property | Typical Value |
|---|---|
| Density | ~7.0 – 7.3 g/cm³ |
| Melting Range | ~230 – 240 °C |
| Electrical Conductivity | Poor |
| Thermal Conductivity | Reduced vs refined tin |
| Surface Appearance | Dull, blistered, porous |
| Magnetic Behavior | Diamagnetic |
Metallurgical Characteristics
Blister tin contains oxide inclusions, intermetallic impurities, gas porosity, and a coarse, non-uniform grain structure.
Strength is impurity-driven and uncontrolled. The material is metallurgically unstable and unsuitable for forming or precision casting.
Corrosion & Chemical Behavior
Corrosion resistance is inferior to refined tin. Impurities create galvanic micro-cells, leading to pitting and uneven oxide formation.
⚠ Not food-safe, electronics-grade, or chemical-grade.
Production & Refining Pathway
Blister tin is produced by reducing cassiterite (SnO₂) with carbon in a furnace. The molten crude tin is cast into rough ingots.
Further refining includes liquation, fire refining, poling, and electrolytic refining to produce ≥ 99.85–99.99% refined tin.
Available Forms
Rough ingots, slabs, and furnace-cast blocks only. No precision or finished commercial forms.
Applications
🏭 Primary use as feedstock for fire-refined and electrolytic refined tin
⚙️ Limited internal foundry recycling or low-spec alloy dilution (rare)
Blister Tin vs Refined Tin
| Feature | Blister Tin | Refined Tin |
|---|---|---|
| Purity | 96 – 99 % | 99.85 – 99.999 % |
| Surface | Blistered | Smooth |
| Mechanical Reliability | Poor | Predictable |
| Industrial Use | Intermediate | Final product |
| Food / Electronics | ❌ No | ✅ Yes |
Summary:
Blister Tin is a crude, intermediate tin product obtained after primary smelting of tin ore.
Its value lies in being an essential feedstock for producing refined tin. Due to high impurity
levels and inconsistent properties, it is unsuitable for direct industrial use.