Aluminium Properties
Aluminium is valued for its light weight, corrosion resistance, and conductivity. Learn which alloys to use for structural, piping, and heat transfer applications.
Overview
Aluminium is one-third the weight of steel, with good corrosion resistance and excellent thermal and electrical conductivity. It is widely used in aerospace, transport, HVAC fins, electrical busbars, and cryogenic applications. Pure aluminium is soft — most engineering uses are alloyed with silicon, magnesium, or copper for strength.
Key Properties
| Property | Value |
|---|---|
| Density | 2700 kg/m³ (1/3 of steel) |
| Tensile strength (6061-T6) | 310 MPa |
| Yield strength (6061-T6) | 276 MPa |
| Melting point | 660°C |
| Thermal conductivity | 237 W/m·K |
| Coefficient of expansion | 23 × 10⁻⁶ /°C (2× steel) |
| Max service temperature | 200°C (structural) |
Common Alloys
| Alloy | Properties | Typical use | |
|---|---|---|---|
| 6061 | Good strength, weldable, versatile | Structural, piping, frames | |
| 6063 | Good extrudability, good finish | Window frames, architectural | Heat exchanger fins |
| 5052 | Good weldability, marine res. | Marine, fuel tanks | |
| 3003 | Good workability, moderate strength | Heat exchanger tubes, sheet | |
| 7075 | Very high strength | Aerospace, military |
Advantages
- Light weight: 1/3 the density of steel — critical for aerospace, transport, and lifting applications.
- Excellent corrosion resistance: Forms a protective oxide layer — resists atmospheric corrosion without painting.
- High thermal conductivity: 237 W/m·K — 5× better than steel. Used for heat exchanger fins and fins on cooling coils.
- Good electrical conductor: 61% IACS — used for overhead power lines (lighter than copper for same capacity).
- Non-toxic: Safe for food contact — used in food processing and packaging.
- Good cryogenic properties: Strength increases at low temperatures — used in LNG and cryogenic plants.
Limitations
- Low melting point: 660°C — unsuitable for high-temperature applications. Structural strength drops rapidly above 150°C.
- High thermal expansion: 2× the expansion of steel — requires careful design for mixed-metal systems.
- Difficult to weld: Requires TIG or MIG with AC current and special procedures — oxide layer must be removed.
- Galling: Aluminium threads gall and seize easily — use anti-seize or stainless inserts.
- Galvanic corrosion: When in contact with copper or steel, aluminium is the anode and corrodes rapidly — isolate with gaskets or coatings.
Chemical Compatibility
| Chemical | Rating |
|---|---|
| Fresh water | Good |
| Seawater | Fair (use 5052 alloy) |
| Dilute acids | Poor |
| Alkalis | Poor — dissolves |
| Organic solvents | Good |
| Ammonia | Good |
How CHI can help
Ask CHI about aluminium properties and to recommend the right alloy for your structural or heat transfer application. The CHI assistant can recommend the right material for your specific application, explain chemical compatibility, and flag when a material is unsuitable for your operating temperature or environment.