If you need formability, corrosion resistance, cost-effectiveness and excellent cold-workability for general-purpose sheet and tankwork, choose 3003. If you need structural strength, machinability, and heat-treatable high-strength parts (frames, fittings, extrusions), choose 6061 (especially T6/T651 tempers). 3003 is a non-heat-treatable Mn-alloy prized for forming and corrosion performance; 6061 is a precipitation-hardening Mg-Si alloy engineered for much higher yield and tensile strength after heat treatment.
Alloy family and intent
3003 is in the 3xxx series (manganese-strengthened, cold-worked) and is widely used where formability and corrosion resistance matter (roofing, tankage, housewares, fuel tanks, HVAC ducting). 6061 is a 6xxx series (magnesium + silicon) precipitation-hardening alloy used for structural applications, extrusions, and higher-strength parts where heat treatment (e.g., T6) produces a large strength boost.
Chemical composition (weight % typical ranges)
| Element | 3003 (typical) | 6061 (typical) |
|---|---|---|
| Aluminum (balance) | Balance (~96.7–99%) | Balance (~97.9–99%) |
| Magnesium (Mg) | 0.05–0.20% | 0.8–1.2% |
| Silicon (Si) | ≤0.6% | 0.4–0.8% |
| Manganese (Mn) | 1.0–1.5% | ≤0.15% |
| Copper (Cu) | 0.05–0.20% | 0.15–0.40% |
| Iron (Fe) | ≤0.7% | ≤0.7% |
| Zinc (Zn) | ≤0.10% | ≤0.25% |
| Other (each/total) | ≤0.05% / ≤0.15% | ≤0.05% / ≤0.15% |
(Sources: alloy datasheets / material handbooks — composition ranges are industry standard design limits).
Mechanical & physical properties (clear comparison)
| Property | 3003-H14 (typical) | 6061-T6 (typical) |
|---|---|---|
| Density | 2.73 g/cm³ | 2.70 g/cm³ |
| Tensile strength (UTS) | ~110–145 MPa | ~310–350 MPa |
| Yield strength (0.2% YS) | ~55–115 MPa (depends on temper) | ~240–275 MPa |
| Elongation (%) | 10–30% | 8–12% |
| Hardness (Brinell) | ~30 HB | ~95 HB |
| Thermal conductivity | Good (~160–200 W/m·K) | Good (~150–180 W/m·K) |
| Typical thickness forms | Sheet, coil, plate | Extrusions, plate, bar, forgings |
| Heat-treatable? | No (strain-hardened) | Yes (precipitation hardening, e.g. T6) |
Key point: 6061 (T6) typically provides ~2–3× the strength of 3003, while 3003 keeps superior forming ductility and lower cost for non-structural parts.
Workability: forming, welding, machining, heat treatment
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Forming / cold work: 3003 is far easier to deep-draw, roll, and stamp; it is often supplied in H-tempers (H14, H18) for good shape retention. 6061 can be formed (especially in O or H111 tempers), but its lower ductility in T6 makes complex forming tougher and more prone to cracking.
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Welding: Both alloys are weldable with common filler alloys, but 3003 welds readily by TIG/MIG for sheetwork. 6061 welds fine but the heat-affected zone reduces local strength; post-weld heat treatment is not usually practical for complex structures. When joining 3003 to other alloys, 4043 filler is often recommended.
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Machining: 6061 is much more machinable than 3003 (machine cuts, threads, tapped holes) and is commonly used for CNC parts. 3003 is softer and gums up cutting tools; machining is possible but less efficient.
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Heat treatment: 3003 is non-heat-treatable (strength via cold work). 6061 is heat-treatable — solution treat + artificial aging (T6) produces a large jump in strength and hardness, which is the core reason 6061 is used for structural and aerospace components.
Tempers, standards and identifiers
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Common tempers: 3003-H14 (commercially cold-worked); 6061-T6 and T651 (solutionized, artificially aged; T651 is stress-relieved stretched).
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UNS numbers / EN AW: 3003 is often UNS A93003 (sometimes listed simply as 3003), 6061 is UNS A96061 / EN AW-6061.
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Relevant specs/standards: ASTM B209 (aluminum and aluminum-alloy sheet and plate) commonly covers both when sold as sheet/plate; AMS/ASME/EN standards exist for plate, extrusions and forgings depending on application. For plate/flat products, refer to ASTM B209 and supplier AMS numbers for aerospace or critical parts.
Typical applications — where each alloy shines
3003 (best when):
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Roofing, gutters, siding, HVAC ducts
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Fuel tanks, tanks and pressureless vessels for chemicals and food handling
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Decorative trim, signage, cookware, and general sheet metal forming
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Applications that need rust-free behavior, high formability, and low cost.
6061 (best when):
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Structural frames, bicycle components, machine parts, truck bodies (structural elements)
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Extruded profiles (window frames, railings), marine fittings, aircraft substructures (non-primary), precision machined components
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Situations where higher strength, machining accuracy and heat-treat performance are required.
Equivalents & interchangeability (simple table)
| Alloy | Typical equivalents / notes |
|---|---|
| 3003 | EN AW-3003, UNS A93003. Close alternatives for certain sheet applications: 3105, 3004 for similar formability. Not interchangeable where higher strength needed. |
| 6061 | EN AW-6061, UNS A96061. Nearby alternatives: 6063 (more formable extrusions but lower strength), 6082 (higher strength in some tempers). Not interchangeable with 3003 in structural roles. |
Global price snapshot — 2025 (market context + comparative table)
Important context: alloy prices track the primary aluminum commodity (LME) plus processing premiums, alloying element costs, regional tariffs, and fabrication value. 2025 has seen volatile regional premiums due to supply constraints, tariffs and demand shifts. Use the figures below as indicative ranges (FOB/spot) for common industrial sheet/extrusion material in mid-2025 — not firm quotes. Sources: LME/commodity indices, China export snapshots, industry price reports.
| Region / Product | Indicative 2025 price (USD/metric ton) | Notes / source |
|---|---|---|
| Primary LME aluminum (spot, Aug 2025) | $2,600–2,650 / t | LME index (commodity baseline). |
| 3003 sheet (China FOB, 2025) | $2,700–2,900 / t | Built from Chinese export listings and market reports. Lower value-added sheet. |
| 6061 sheet/extrusion (general FOB 2025) | $2,900–3,300 / t | Higher processing and alloy premium for Mg+Si content and heat treatment; USA/Europe premiums often higher. |
| US domestic (with tariffs/surcharges, 2025) | +15–30% vs FOB global | Tariffs/premia reported to lift US prices in 2025 (industry news). |
How to read this: 3003 often trades at or just above primary aluminum because it is low alloy, minimal processing. 6061 carries a premium for alloying and heat-treat processing and thus is typically pricier per ton. Local supply, order size, and certification (e.g., aerospace AMS) can cause wide spreads.
Design notes, finishes, corrosion behaviour
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Corrosion resistance: 3003 has very good resistance to atmospheric corrosion and is commonly used outdoors and in contact with many chemicals. 6061 also resists corrosion well (especially in T6) but in marine chlorides 5xxx series like 5083/5052 outperform both; anodizing improves corrosion and wear properties for both alloys.
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Finishes & coating: both alloys accept anodizing and paint systems; surface preparation differs slightly (cleaning, etch) and anodizing appearance depends on alloy composition.
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Fatigue & fracture: aluminium alloys are not as fatigue-resistant as some steels; 6061 generally performs better in dynamic loading due to higher strength, but design must still include proper stress relief, fillets and surface finish.
Procurement & supplier tips for buyers (practical)
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Specify temper & standard: always request the alloy + temper + standard (e.g., 6061-T6 per ASTM B209 or AMS4027 for aerospace). For sheet, specify thickness, finish, and certifications (mill test report, chemical/physical tests).
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Batch testing: for critical parts, insist on MTRs (mill test reports), hardness checks and composition certificates. For welded structures with 6061, consider stress-relief or re-engineering joints to avoid losing local strength.
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Buy on value, not only metal cost: 6061’s machining time may be shorter (better machinability) and may reduce finished-part cost despite higher alloy price. 3003 may save material cost but increase forming work hours if parts are complex.
FAQs
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Which alloy is stronger, 3003 or 6061?
Answer: 6061 (especially T6) is substantially stronger — roughly 2–3× tensile/yield vs 3003. -
Can I form 6061 like 3003?
Answer: Not as easily. 3003 is far more formable; 6061 in T6 is much less ductile and better suited to machining and extrusion than deep drawing. -
Is 3003 suitable for fuel tanks or food contact?
Answer: Yes — 3003 is commonly used for fuel tanks, food handling equipment and chemical tanks where high formability and corrosion resistance are needed. -
Does welding reduce strength of 6061?
Answer: Local heat from welding softens the HAZ and reduces strength near the weld; post-weld heat treatment is rarely practical, so joint design must account for lower local strength. -
Which alloy costs more in 2025?
Answer: Typically 6061 carries a higher price than 3003 per ton due to alloying and processing premiums; regional variations apply. See price snapshot above. -
Can 3003 be anodized?
Answer: Yes, it accepts anodizing but the appearance differs from 6xxx series; surface finish and etch cycles must be controlled. -
Are there direct drop-in equivalents?
Answer: Not for structural replacement. 3003 and 6061 are designed for different roles; interchange without redesign is not recommended. -
Which is better for CNC machining?
Answer: 6061 is preferred for precision CNC work due to its higher hardness, stable chips and better finishing behaviour.
Practical selection checklist
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Need deep drawing / thin sheet / outdoor trim → 3003.
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Need load bearing, machining, extrusions → 6061-T6.
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Need marine chloride resistance → consider 5xxx series instead of either.
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Need certified aerospace grade → request AMS/ASTM references and MTRs (6061 variants available with AMS/ASTM certification).
Closing summary
Both 3003 and 6061 are staple aluminium alloys — each engineered with trade-offs. One is a cold-work, Mn-strengthened alloy optimized for formability and corrosion resistance (3003); the other is an Mg-Si precipitation-hardenable alloy engineered for strength and machinability (6061). Selecting between them is rarely about “which is better” in the abstract; it is about matching mechanical needs, fabrication methods, and cost targets. Use 3003 where shape and corrosion come first, and 6061 when strength, precision and heat-treatable performance are the priority.
