Forming
O temper accepts deep drawing and tight bends; H24 handles moderate bends with less springback than H14.
Al-Mn rust-proof sheet
3A21 Aluminium Sheet & Plate
3A21 is an aluminium-manganese alloy registered in the GB system that is very close in composition and behaviour to 3003. It is non-heat-treatable, forms and welds easily and resists corrosion well. Metline supplies 3A21 sheet and plate in O, H14, H24 and H112, or 3003 where your drawing allows, certified to GB/T 3880 or ASTM B209, worldwide.
- Alloy
- 3A21 (Al-Mn)
- Tempers
- O, H14, H24, H18, H112
- Thickness
- 0.5 – 120 mm
- Standards
- GB/T 3190 · GB/T 3880
What is 3A21 aluminium?
3A21 belongs to the group of older national designations that use a letter in the second position. It is the counterpart of the Russian AMts (АМц) and is functionally equivalent to AA 3003 and EN AW-3003: a manganese-strengthened aluminium alloy, often called "rust-proof aluminium" because of its corrosion resistance.
Like 3003, 3A21 cannot be heat-treated; strength comes from cold rolling. Annealed sheet is soft and very ductile; H14 and H24 give moderate stiffness for panels and tanks; as-rolled H112 plate is used for thicker parts. The alloy welds and brazes easily and is widely used for fuel tanks and lines, heat exchangers, containers and roofing.
Drawings from Chinese, Russian and CIS design offices frequently specify 3A21, while Western drawings specify 3003. In most applications the two are interchangeable, but the composition limits are not identical, so we always confirm which standard governs before supply.
3A21 vs 3003 chemical composition (wt %)
| Element | 3A21 (GB/T 3190) | 3003 (AA / ASTM) |
|---|---|---|
| Silicon (Si) | ≤ 0.6 | ≤ 0.6 |
| Iron (Fe) | ≤ 0.7 | ≤ 0.7 |
| Copper (Cu) | ≤ 0.20 | 0.05 – 0.20 |
| Manganese (Mn) | 1.0 – 1.6 | 1.0 – 1.5 |
| Magnesium (Mg) | ≤ 0.05 | — |
| Zinc (Zn) | ≤ 0.10 | ≤ 0.10 |
| Titanium (Ti) | ≤ 0.15 | — |
| Others, each / total | 0.05 / 0.10 | 0.05 / 0.15 |
| Aluminium (Al) | Remainder | Remainder |
3A21 allows a slightly wider manganese range and has no minimum copper; 3003 requires 0.05 % copper minimum. Values summarised from GB/T 3190 and the Aluminum Association registration; check the edition named on your drawing.
3A21 mechanical and physical properties
Typical values below are for guidance; GB/T 3880.2 sets guaranteed ranges by temper and thickness, and these are reported on the certificate.
| Temper | Tensile strength (typical) | Yield strength (typical) | Elongation (typical) |
|---|---|---|---|
| O | 100 – 130 MPa | about 40 – 50 MPa | 20 – 30 % |
| H14 / H24 | 145 – 180 MPa | about 125 – 150 MPa | 5 – 10 % |
| H18 | 185 – 210 MPa | about 170 – 190 MPa | 2 – 4 % |
| H112 (plate) | 110 – 140 MPa | about 50 – 70 MPa | 15 – 20 % |
Physical properties (typical)
- Density
- 2.73 g/cm³
- Thermal conductivity
- about 160 – 190 W/m·K depending on temper
- Electrical conductivity
- about 40 – 50 % IACS
- Melting range
- about 643 – 654 °C
3A21 standards and equivalents
| System | Designation | Standard |
|---|---|---|
| China (GB) | 3A21 (formerly LF21) | GB/T 3190 (composition), GB/T 3880 (sheet and plate) |
| Russia / CIS | AMts (АМц) | GOST 4784, GOST 21631 |
| Aluminum Association / ASTM | 3003 (closest) | ASTM B209 |
| European (EN) | EN AW-3003 (closest) | EN 485, EN 573-3 |
| Japan (JIS) | A3003P (closest) | JIS H4000 |
Because 3A21 is an Al-Mn alloy, it is non-heat-treatable. Any reference to "T" tempers (T3, T4, T6) for 3A21 is an error; the correct tempers are O and the strain-hardened H tempers.
3A21 sheet and plate sizes
Supply range
- O-temper sheet
- 0.5 – 6 mm; 1000 × 2000, 1200 × 3000, 1250 × 2500, 1500 × 3000 mm
- H14 / H24 sheet
- 0.5 – 6 mm in the same formats
- H112 plate
- 6 – 120 mm, typically 1500 × 3000 mm
- Surface
- Mill finish, PVC film, embossed, anodised or painted on request
- Processing
- Cutting to size, bending, punching and welding preparation
| Thickness (mm) | kg per m² | 1220 × 2440 mm (kg) | 1500 × 3000 mm (kg) |
|---|---|---|---|
| 0.5 | 1.36 | 4.1 | 6.1 |
| 1 | 2.73 | 8.1 | 12.3 |
| 1.5 | 4.09 | 12.2 | 18.4 |
| 2 | 5.46 | 16.3 | 24.6 |
| 3 | 8.19 | 24.4 | 36.9 |
| 4 | 10.9 | 32.5 | 49.1 |
| 5 | 13.7 | 40.6 | 61.4 |
| 6 | 16.4 | 48.8 | 73.7 |
| 8 | 21.8 | 65.0 | 98.3 |
| 10 | 27.3 | 81.3 | 122.9 |
| 12 | 32.8 | 97.5 | 147.4 |
| 16 | 43.7 | 130.0 | 196.6 |
| 20 | 54.6 | 162.5 | 245.7 |
| 25 | 68.2 | 203.2 | 307.1 |
| 30 | 81.9 | 243.8 | 368.6 |
| 40 | 109.2 | 325.1 | 491.4 |
| 50 | 136.5 | 406.3 | 614.2 |
| 60 | 163.8 | 487.6 | 737.1 |
| 80 | 218.4 | 650.1 | 982.8 |
| 100 | 273.0 | 812.7 | 1228.5 |
| 120 | 327.6 | 975.2 | 1474.2 |
Working with 3A21
Welding
TIG, MIG and gas welding with Al-Mn (such as the GB SAlMn type) or ER4043 filler. Brazing is straightforward.
Corrosion
Very good in the atmosphere, fresh water and petroleum products, which suits fuel tanks and lines.
Applications of 3A21 sheet and plate
- Fuel and lubricant tanks and lines for vehicles, aircraft ground equipment and machinery
- Heat exchangers and brazed plate exchangers
- Liquid containers, cookware and washing-machine drums
- Roofing, patterned and acoustic panels, vehicle body skins
- Road signs and general sheet metal parts with light loads
How to order 3A21 sheet
- SpecifyAlloy and standard (3A21 to GB/T 3880, or 3003 to ASTM B209), temper, thickness, size, quantity and finish.
- QuoteWe confirm availability, tolerances, certification, packing and delivery terms (EXW, FOB, CIF or DAP) for your destination.
- ProcessSheets are cut, film-protected if required and inspected.
- DocumentEach delivery carries a mill test certificate to EN 10204 3.1 with the cast analysis and mechanical results for the lot; third-party inspection can be arranged on request.
- ShipSheets are interleaved or film-protected, packed on pallets or in seaworthy wooden cases, and shipped by sea or air to your port or door.
References and standards
- GB/T 3190 – Chemical composition of wrought aluminium and aluminium alloys
- GB/T 3880 – Wrought aluminium and aluminium alloy plates, sheets and strips for general engineering
- ASTM B209 – Standard Specification for Aluminum and Aluminum-Alloy Sheet and Plate
- The Aluminum Association – International Alloy Designations and Chemical Composition Limits for Wrought Aluminum (Teal Sheets)
3A21 aluminium sheet: frequently asked questions
Is 3A21 the same as 3003?
They are very close and interchangeable in most uses. 3A21 allows manganese up to 1.6 % and has no minimum copper; 3003 requires 0.05 – 0.20 % copper. Confirm acceptance with the design authority for critical parts.
Can 3A21 be heat-treated?
No. It is an Al-Mn alloy strengthened only by cold work. Correct tempers are O, H14, H24, H18 and H112.
What is the old name for 3A21?
It was formerly designated LF21 in the Chinese system and corresponds to AMts in the Russian GOST system.
Can you supply 3003 instead of 3A21?
Yes, if your specification allows it. We can supply either and certify to the governing standard.
What is 3A21 used for?
Fuel tanks and lines, heat exchangers, containers, cookware, roofing and lightly loaded sheet metal parts.
Need 3A21 or 3003 sheet?
Send temper, size, quantity and governing standard. We will reply with availability and a delivered price.
