Key Takeaways
- Aluminum density is about 2.70 g/cm³ - roughly one-third of steel (7.85 g/cm³) - which is why replacing steel with aluminum cuts component weight by about two-thirds for the same volume.
- Strength is set by alloy and temper, not by the metal alone. Typical tensile strength spans about 90 MPa (1100-O) to more than 500 MPa (7075-T6).
- A self-healing oxide film gives aluminum good resistance to air and many neutral media, but the film dissolves in strong acids and strong alkalis, and galvanic corrosion must be managed at contacts with copper or steel.
- EC-grade conductor alloys reach about 62% IACS - roughly two-thirds of copper's conductivity by volume and about twice copper's by weight.
- Remelting aluminum scrap uses about 95% less energy than primary smelting, and the metal can be recycled repeatedly without losing its properties.
Aluminum plate is a flat-rolled product made from pure aluminum or one of its alloys. It is specified wherever weight, corrosion life, conductivity, or recyclability matters more than raw material cost. This article covers the performance characteristics that decide material selection: physical properties, mechanical strength across alloy series, corrosion behavior and its limits, a direct comparison with steel and copper, typical applications, and the limitations every buyer should know. Property values below are typical published figures; confirm the exact numbers against the mill test certificate for your ordered grade and temper.
1. What is an Aluminum Plate
Under ASTM B209/B209M, the difference is thickness: sheet is up to 6.35 mm (0.250 in) thick; plate is thicker than 6.35 mm. Both are produced in alloy families 1xxx–8xxx with a temper code that describes how the material was processed: O (annealed, softest), H (strain-hardened), or T (heat-treated, including T6 peak-aged). The full designation - for example 5052-H32 or 6061-T6 - tells you both composition and processing, and the performance characteristics follow from those two pieces of information.
2. Core Physical Properties of Aluminum
The table below lists the physical values that buyers most often ask for. All figures are typical values for commercial grades, consistent with data published under ASTM, ISO 209, and EN 573.
| Property | Typical value | Notes |
|---|---|---|
| Density | 2.70 g/cm³ (2,700 kg/m³) | About one-third of steel (7.85 g/cm³); the basis of aluminum's weight advantage |
| Melting point | ≈ 660 °C (pure); 500–660 °C for alloys | Alloying lowers the melting range; service temperature limits are far below this |
| Thermal conductivity | 117–237 W/(m·K) | Grade-dependent: 1100 ≈ 222; 6061-T6 ≈ 167; 5083 ≈ 117 W/(m·K) |
| Electrical conductivity | 59–62% IACS | EC 1350 ≈ 61.8% IACS; 1100 ≈ 59% IACS (IACS = International Annealed Copper Standard) |
| Modulus of elasticity | ≈ 69 GPa | About one-third of steel (≈ 200 GPa); affects stiffness design |
| Magnetic properties | None | Non-magnetic and non-sparking; safe near instruments and in explosive atmospheres |
| Surface reflectivity | High | Supports lighting reflectors, solar reflectors, and thermal insulation foil |
Typical values, grade-dependent. Verify against the mill test certificate of the ordered alloy and temper.
3. Mechanical Strength Depends on Alloy and Temper
Pure aluminum (1xxx series) is soft and low-strength - a tensile strength of roughly 90 MPa in the annealed condition. "High strength" only becomes true when aluminum is alloyed and processed. The series system is the quickest way to navigate this: the first digit of the grade tells you the main alloying element, and with it the typical strength, corrosion resistance, and formability.
| Series | Main alloying elements | Typical tensile strength (MPa) | Strength | Corrosion resistance | Formability | Representative uses |
|---|---|---|---|---|---|---|
| 1xxx | ≥ 99% Al | 75–140 | Low | Excellent | Excellent | Foil, food packaging, electrical conductors (1350) |
| 2xxx | Copper | 190–480 (T3/T6) | High | Moderate to low | Moderate | Aircraft structures, truck panels |
| 3xxx | Manganese | 110–285 | Low–moderate | Good | Excellent | Roofing, cooking utensils, storage tanks (3003) |
| 4xxx | Silicon | 120–300 | Moderate | Good | Good | Welding wire, brazing sheet, forgings |
| 5xxx | Magnesium | 125–350 | Moderate–high | Excellent (marine) | Good | Marine plate, pressure vessels, transport (5052, 5083) |
| 6xxx | Magnesium + silicon | 125–330 (T6) | Moderate–high | Good; anodizes well | Good | Structural plate, extrusions, machined parts (6061, 6063) |
| 7xxx | Zinc + magnesium | 220–570 (T6) | Highest | Moderate | Fair | Aerospace, high-load components (7075) |
Typical values for commercial grades per ASTM B209/B209M and published mill data; exact figures depend on thickness, temper, and test direction.
Temper matters as much as alloy: two plates with the same alloy but different tempers can differ in strength by a factor of two or more. A 6061-O plate has a typical tensile strength near 125 MPa; the same 6061 in T6 reaches about 290 MPa. Always specify both grade and temper on the order.
4. Corrosion Resistance
Aluminum's corrosion behavior is defined by its surface oxide film. The film is only about 2.5–4 nm thick, forms instantly in air, and repairs itself when scratched. In the atmosphere, fresh water, and many neutral media, this makes aluminum durable without any coating - which is why 5xxx alloys are the standard choice for marine and coastal exposure.
Aluminum does not "rust" - rust means iron oxide, and aluminum contains no iron. It corrodes in its own way: the oxide film dissolves in strong acids and strong alkalis (caustic cleaning solutions, sodium hydroxide, contact with fresh concrete or cement), after which the metal is attacked rapidly. Alkaline environments are the main corrosion risk, not atmospheric exposure.
Galvanic corrosion: coupling aluminum with copper, brass, or steel in a wet electrolyte accelerates attack on the aluminum member. Use isolating gaskets, coatings, or compatible fasteners, or design the joint for it.
Salt exposure: most alloys survive mild salt-laden air; for permanent splash-zone or seawater service, select 5xxx marine grades (5083, 5086) or apply protective finishing.
Surface protection: anodizing (per ISO 7599 / MIL-A-8625 type II/III), powder coating, or painting extends service life and adds appearance options - anodized and mirror-finish plates are common in architectural work.
5. Aluminum vs Steel vs Copper
| Property | Aluminum (typical) | Steel (structural) | Copper |
|---|---|---|---|
| Density (g/cm³) | 2.70 | 7.85 | 8.96 |
| Typical tensile strength (MPa) | 90–570 (by alloy and temper) | 400–550 (mild/structural) | 220–380 (annealed to hard drawn) |
| Modulus of elasticity (GPa) | 69 | ≈ 200 | 117 |
| Electrical conductivity (% IACS) | ≈ 62 (EC 1350) | ≈ 10 | 100 (IACS reference) |
| Conductivity per unit weight | About 2× copper | - | Reference |
| Atmospheric corrosion | Good - self-protecting film | Rusts without coating | Good; tarnishes |
Typical values; aluminum figures per ASTM B209 and IACS scale, steel per structural steel standards, copper per ASTM B152/IACS.
Three comparisons matter in practice. For current-carrying duty, an aluminum conductor needs about 1.6× the cross-section of copper (100 ÷ 62) to carry the same current, but it weighs roughly half as much - the reason overhead lines and bus bars use aluminum. For stiffness, aluminum's modulus is one-third of steel's, so an aluminum beam must be deeper or thicker to match deflection. For strength at equal weight, 5xxx/6xxx/7xxx alloys are competitive with mild steel, which is why aircraft, ship decks, and truck bodies are built in aluminum.
6. Typical Applications of Aluminum Plate
- Transportation: truck bodies and trailers (5xxx, 6xxx), aircraft skins and spars (2xxx, 7xxx), rail cars, marine hulls (5083, 5086).
- Building and construction: curtain-wall panels, roofing, ceiling systems (3xxx, 5xxx), mirror and perforated decorative sheets with anodized finishes.
- Packaging: foil stock (1xxx, 8xxx), food containers, pharmaceutical and flexible packaging foil.
- Electrical: bus bars, overhead conductor plate, transformer components, heat sinks (1xxx, 6xxx).
- Industrial: pressure vessels, cryogenic tanks (5083), heat exchangers, jigs and tooling plates (6061).
7. Limitations Every Buyer Should Know
An honest material guide lists the limits as well as the strengths. Aluminum plate has five that matter for engineering decisions:
- Lower absolute strength and stiffness than steel - select alloys and temper, and design sections for a 69 GPa modulus rather than steel's ≈ 200 GPa.
- Fatigue without an endurance limit - unlike steel, aluminum's stress-life (S-N) curve keeps falling with more cycles; cyclic-load design must use real fatigue data, not a "safe" stress cap.
- Temperature limits - strength drops noticeably above roughly 150–200 °C (alloy-dependent), and creep becomes a design constraint in hot service.
- Weldability varies - 5xxx and 6xxx weld well with the correct filler; 2xxx and 7xxx are difficult to weld and may lose strength in the heat-affected zone.
- Galvanic corrosion in mixed-metal assemblies - see Section 4; joints with copper or steel need isolation.
Cost is also part of the picture: aluminum plate costs more per tonne than structural steel. The economic case rests on weight saving, corrosion life, electrical conductivity, or recyclability - quantify those before switching materials.
FAQ
Is aluminum plate strong enough for structural use?
Yes, when you choose the right alloy and temper. 6061-T6 (typical tensile ≈ 290 MPa) and 5083-H116 (≈ 290–315 MPa) are used in truck frames, ship structures, and building frames. Design must account for aluminum's lower modulus (69 GPa vs ≈ 200 GPa for steel), so sections are often deeper or thicker.
Does aluminum plate rust?
No - rust is iron oxide, and aluminum contains no iron. Aluminum corrodes in its own way: the natural oxide film protects it in air and neutral media, but strong acids and alkalis dissolve the film, and salt water requires marine-grade alloys (5xxx) or protective finishing.
Why is aluminum called lightweight?
Because of density: 2.70 g/cm³ vs 7.85 g/cm³ for steel. For the same volume, aluminum weighs about one-third of steel; a steel part replaced by an aluminum part of equal stiffness weighs roughly half, because the aluminum section is deeper.
What is the difference between 5052 and 6061 plate?
5052 (aluminum-magnesium) is strain-hardened, with excellent corrosion resistance and formability - the common choice for marine and tank applications. 6061 (aluminum-magnesium-silicon) is heat-treatable: higher strength in T6 (≈ 290 MPa tensile), better machinability, good anodizing response, and the default general-purpose structural grade. Choose 5052 for corrosion and forming; choose 6061 for strength and machining.
Can aluminum plate be welded?
5xxx and 6xxx alloys weld well with the correct filler (for example, ER5356- or ER4043-type filler per AWS A5.10). 2xxx and 7xxx alloys are generally considered difficult to weld - they may lose strength in the heat-affected zone - so mechanical joining is often preferred for those series.
Is aluminum a good electrical conductor?
Yes for weight-critical conductors. EC-grade alloys (1350) reach about 62% IACS: a conductor with the same current capacity needs about 1.6× the cross-section of copper but weighs roughly half, which is why overhead lines and bus bars use aluminum.
