If you are choosing between 5052 and 5083 aluminum and only remember one thing, make it this: 5083 is the hull, 5052 is everything bolted or formed onto the hull. 5083 carries more magnesium, is about a third stronger, and comes in marine tempers that a classification society will accept. 5052 is easier to form, cheaper, and is the default for tanks, deckhouses and interior structure.
The two grades are close enough on paper that a drawing will sometimes name both, and close enough in the shop that a fabricator will quietly substitute one for the other. The substitution matters because of one property that does not show up in a tensile table: intergranular corrosion resistance in seawater.
What actually separates them
Both are aluminum-magnesium (5xxx) alloys. The difference is how much magnesium, and what that magnesium does to the material in service.
| 5052 | 5083 | |
|---|---|---|
| Magnesium | 2.2 – 2.8% | 4.0 – 4.9% |
| Typical tensile (H32/H116) | ~230 MPa | ~320 MPa |
| Typical yield | ~180 MPa | ~230 MPa |
| Marine tempers | none formal | H116, H321 (to ASTM B928) |
| Weldability | excellent | excellent, but needs care |
| Formability | good, tight bends OK | limited, cold bends crack |
| Relative cost | lower | higher |
The magnesium is what buys strength and seawater resistance, and it is also what creates the risk. When a high-magnesium 5xxx alloy sits for long periods above about 65 °C, the magnesium precipitates along grain boundaries, and the material becomes susceptible to intergranular corrosion. In a hull that is welded, that shows up as attack alongside the weld.
The fix for 5083 is the temper. H116 and H321 are produced to ASTM B928 with a controlled microstructure that resists intergranular corrosion, and those are the tempers classification societies such as ABS, DNV and Lloyd's Register actually approve for hull plating. 5052 has no equivalent marine temper because it does not need one — at 2.2–2.8% magnesium it stays well below the sensitization threshold in normal service.
When to specify 5083
- Hull plate and welded shell structure. Anything that carries the boat, sits in seawater, and is joined by welding.
- Pressure vessels and cryogenic tanks. 5083 retains toughness down to cryogenic temperature, which is why it is used for LNG and industrial gas tanks.
- Where a classification society is involved. The class rules name the temper, and "5083-H321" is the answer they expect to see on the plate certificate.
For hull plate, the order should state the classification society, the temper (H116 or H321), and the certificate level — normally EN 10204 3.1 with the heat number marked on the plate. This is one of the few aluminum purchases where you genuinely cannot skip the mill certificate.
When to specify 5052
- Formed parts. Deckhouses, engine covers, tank lids, chine and transom pieces that need to bend on a brake press. 5052 takes tight radii that would crack 5083.
- Fuel, water and holding tanks. 5052 is the standard tank alloy — weldable, corrosion-resistant, and the right price point for a part that is mostly flat sheet.
- Interior and non-structural work. Trim, lockers, hatches, anything where strength is not the deciding factor.
A useful rule of thumb from fabrication shops: use 5052 up to about 4–5 mm for formed work, and step up to 5083 for plate from 6 mm upward where welding and structure dominate. The transition is not arbitrary — it is roughly where the forming advantage of 5052 stops mattering and the strength of 5083 starts paying for itself.
What gets specified wrong
The most common mistake is ordering 5083 in plain H32 or H111 for a hull because it is cheaper. Plain H32 is not a marine temper — it has not been through the B928 process that controls intergranular corrosion — and a surveyor or class inspector will reject it. If the plate does not say H116 or H321, it is not marine plate no matter what the seller calls it.
The second mistake is assuming 5052 and 5083 can be freely swapped on a drawing that names one of them. They cannot, for two reasons. The composition limits differ, so a mill certificate naming 5052 does not satisfy a drawing calling for 5083. And the forming behaviour is different — a 5083 part bent to a 5052 radius will crack at the bend.
The third mistake is welding 5083 with the wrong filler. 5083 hull plate is welded with 5183 or 5356 filler, not 4043. 4043 is the wrong family (Al-Si) for a high-magnesium base and will not give a matching-corrosion joint.
The decision in one table
| You need | Choose | Temper | Filler |
|---|---|---|---|
| Hull plate, welded structure | 5083 | H116 / H321 | 5183 / 5356 |
| Formed tanks and deckhouses | 5052 | H32 / O | 5356 |
| Cryogenic or pressure vessel | 5083 | H321 / O | 5183 |
| Interior, trim, non-structural | 5052 | H32 | 5356 |
Bottom line
The choice is strength against formability, and certification against price. 5083 is what you specify when the part is welded, load-bearing and wet; 5052 is what you specify when the part is formed and cost-sensitive. If a class society is anywhere in the picture, the decision is made for you — 5083 in H116 or H321, on a 3.1 certificate, with the filler matched to the base.
For the 5052 and 5083 property tables, see the grade reference pages. If you are quoting a hull or tank package, send the drawing and the class rules — we will tell you which temper and certificate the job actually needs.