For most sheet metal parts in South Africa, the choice comes down to four aluminium grades: 1050 for soft, easy forming, 5052 as the all-rounder, 5083 for marine and heavy-duty work, and 6082 when you need strength in plate. Pick by how the part will be bent, welded, and used, not by which number sounds strongest.
The grade decides whether a bracket bends cleanly or cracks along the fold, and whether a boat fitting lasts or pits. The number is only half the story, too: the temper after it (H14, H32, T6) matters as much. Below we explain how the numbering works, what each common grade is good at, and how they behave on the press brake.
How aluminium grades are numbered
Wrought aluminium alloys use a four-digit number. The first digit tells you the main alloying element, which tells you a lot about how it behaves.
- 1xxx: essentially pure aluminium, 99% or more. Soft, very formable, very corrosion-resistant, low strength.
- 2xxx: copper. Strong, used in aerospace, but poorer corrosion resistance. Rare in general sheet metal work.
- 3xxx: manganese. A bit stronger than pure aluminium and still easy to form (3003 is the common one).
- 5xxx: magnesium. Good strength without heat treatment, excellent corrosion resistance, weldable. The marine series.
- 6xxx: magnesium and silicon. Heat-treatable for higher strength, used for extrusions and plate.
- 7xxx: zinc. Very strong, used in aerospace and high-performance parts, generally not for welded sheet work.
The 1xxx, 3xxx, and 5xxx series get their strength from cold work (rolling). The 6xxx series gets it from heat treatment. That difference shows up when you bend and weld them.
What the temper code means
The letters and numbers after the grade tell you its condition. The common ones on sheet and plate:
- O: annealed, fully soft. Bends easily, lowest strength.
- H14: work-hardened to about half hard. Common on 1050 sheet.
- H32: work-hardened and stabilised, about quarter hard. Common on 5052.
- H111, H116, H321: variants seen on 5083. H116 and H321 are the tempers usually specified for marine work.
- T6: solution heat-treated and artificially aged. Full strength for 6xxx alloys, and the hardest to bend.
So "5052" alone isn't a full specification. "5052-H32" is.
The common grades compared
These are the grades South African suppliers commonly stock as sheet and plate.
| Grade | Type | Strength | Formability | Weldability | Corrosion resistance | Typical uses |
|---|---|---|---|---|---|---|
| 1050 (H14) | Pure aluminium | Low | Excellent | Very good | Very good | Covers, flashings, signage, reflectors, light-duty parts |
| 5052 (H32) | Aluminium-magnesium | Medium | Very good | Good | Excellent, including marine air | Enclosures, brackets, tanks, vehicle and trailer parts |
| 5083 | Aluminium-magnesium | Medium to high | Good | Very good | Excellent, including seawater | Boat parts, marine fittings, truck bodies, pressure vessels |
| 6082 (T6) | Aluminium-magnesium-silicon | High | Poor in T6 | Good, but softens near weld | Good | Structural plate, base plates, machined and flat parts |
Which grade for which job?
1050: soft and cheap to form
1050 is the one to use when the part is mostly about shape, not strength. It bends easily, takes tight radii, and has a clean, bright surface. Think of a 1 mm cover, a flashing, a decorative panel, or a sign. Its weakness is dents. It's soft, so it marks and deforms if knocked.
5052: the sensible default
If you're not sure, 5052 is usually a safe answer. It's noticeably stronger than 1050, still bends well with a radius around 1× thickness, welds well, and resists corrosion in marine air. A 2 mm 5052 enclosure or bracket is a very typical part.
5083: marine and heavy-duty
5083 is the strongest of the common non-heat-treated grades, with excellent resistance to seawater and industrial chemicals. It's the standard choice for boat hulls and fittings, and it keeps its strength well after welding, which suits welded structures. In soft tempers it bends much like 5052; harder tempers and thicker plate want a more generous radius.
6082: strong, but plan your bends
6082-T6 is the strongest of the four and machines well, which is why it's common as plate. But in the T6 temper, it doesn't like tight bends. As a starting rule, plan an inside radius of 1.5–3× thickness or more, and avoid bending parallel to the rolling direction. Welding also softens the metal next to the weld, losing a significant part of its T6 strength. If your part is mostly bent sheet, 5052 or 5083 is often the better choice.
How the grades bend
Bending is where the grade really shows. Rules of thumb for inside bend radius:
- 1050 and 3xxx (soft tempers): about 1× thickness, sometimes less
- 5052-H32: about 1× thickness
- 5083: about 1× thickness in soft tempers, more in harder tempers and thicker plate
- 6082-T6: 1.5–3× thickness or more
Grain direction matters too. Aluminium cracks more easily when the bend line runs parallel to the rolling direction of the sheet. On harder grades, orient bends across the grain where you can, or note the grain direction on the drawing. Our post on bending aluminium without cracking goes deeper on radii and grain.
Our CNC bending service bends aluminium as well as steel, and the grade and temper on your drawing tell us which tooling and radius to use.
Corrosion, mixing metals, and coating
All four grades resist atmospheric corrosion well, thanks to aluminium's natural oxide film. The 5xxx series is the pick near the sea.
Watch out when aluminium touches other metals. Stainless bolts, steel brackets, or copper in contact with aluminium in wet conditions can make the aluminium corrode at the joint. Isolate them with washers or sealant. Our guide to galvanic corrosion explains why.
All the common grades can be powder coated for colour. If you're still deciding whether aluminium is right at all, compare it in aluminium vs steel sheet.
What to put on your quote
Give the grade and temper if you know them (for example, "5052-H32, 2 mm"), the quantity, and any bending, welding, or coating. If you don't know the grade, say what the part does and where it lives, and choose "Not sure yet". Start a quote for CNC bending and add laser cutting and finishing to the same order.