H116
Strain-hardened and processed to meet the exfoliation and intergranular corrosion tests of ASTM B928 / EN 13195. The standard temper for hull plating below the waterline.
Shipbuilding materials
Marine Grade Aluminium Plate: Choosing the Right Alloy
"Marine grade" aluminium plate means 5xxx Al-Mg alloys, chiefly 5083, 5086, 5383, 5059 and 5456, supplied in H116 or H321 temper and tested to ASTM B928 or EN 13195 for resistance to exfoliation and intergranular corrosion. This guide compares the grades, explains the tempers and class-society approvals, and shows where 5052, 5754 and 6xxx alloys fit on a vessel. Metline supplies marine plate, sheet and related products to shipyards and fabricators worldwide.
- Core grades
- 5083 · 5086 · 5383 · 5059
- Tempers
- H116 · H321 · H111
- Standards
- ASTM B928 · EN 13195
- Approvals
- DNV, ABS, LR, BV and others
What makes aluminium plate "marine grade"?
Any aluminium alloy can survive sea air for a while. A marine grade plate is one that keeps its strength and integrity when it is welded, immersed in seawater and stressed for decades. That combination points to the non-heat-treatable Al-Mg alloys with roughly 3 – 5.5 % magnesium.
Magnesium in solid solution strengthens the alloy without forming the copper- or zinc-rich particles that make 2xxx and 7xxx alloys corrode in salt water. Because the strength comes from magnesium and cold work rather than heat treatment, welding softens the heat-affected zone far less than it softens a 6xxx alloy. The result is a hull material that is light, weldable and tough at low temperature.
The weakness of high-magnesium alloys is sensitisation: held at 65 – 200 °C, magnesium-rich beta phase can form a continuous network along grain boundaries, making the plate prone to intergranular corrosion and exfoliation. The special H116 and H321 tempers, and the corrosion tests in ASTM B928 and EN 13195, exist to control exactly this. Plate certified to those standards is what shipyards and class societies mean by marine grade.
Marine aluminium plate grades compared
| Alloy | Mg (approx.) | Strength level | Typical marine use |
|---|---|---|---|
| 5083 | 4.0 – 4.9 % | High | The default hull, deck and bulkhead plate for workboats, ferries, patrol craft and yachts |
| 5383 | 4.0 – 5.2 % | Higher than 5083, incl. welded | High-speed craft and large aluminium ships where weight saving justifies the cost |
| 5059 | 5.0 – 6.0 % | Highest of the 5xxx marine plates | Fast ferries, naval and military craft, thinner hull plating |
| 5456 | 4.7 – 5.5 % | Higher than 5083 | Naval vessels and hulls built to US practice |
| 5086 | 3.5 – 4.5 % | Medium-high | Hulls and decks where lower sensitisation risk than 5083 is preferred, especially in the US |
| 5052 | 2.2 – 2.8 % | Medium | Small boats, fuel tanks, interior and superstructure panels; easy to form |
| 5754 | 2.6 – 3.6 % | Medium | Superstructures, interior structures, tanks; common in European yards |
| 5454 | 2.4 – 3.0 % | Medium | Parts that may run warm (above ~65 °C), where higher-Mg alloys risk sensitisation |
| 6061 / 6082 | Mg + Si | High (T6) | Extruded stiffeners, frames, masts, deck fittings; not for immersed plating |
Marine designations used in GOST and GB/T standards (for example 5A01, 5A05, 5A06, 5A30) are Al-Mg alloys in the same family; their nearest internationally registered counterparts are covered on our individual grade pages.
Specified minimum properties of H116 plate
| Alloy and temper | Tensile strength, min | Yield strength (0.2 %), min | Elongation, min |
|---|---|---|---|
| 5083-H116 / H321 | 305 MPa (44 ksi) | 215 MPa (31 ksi) | 10 – 12 % |
| 5086-H116 | 275 MPa (40 ksi) | 195 MPa (28 ksi) | 8 – 10 % |
| 5456-H116 / H321 | 315 MPa (46 ksi) | 230 MPa (33 ksi) | 10 – 12 % |
| 5083-O / H111 | 270 – 275 MPa | 115 – 125 MPa | 12 – 16 % |
Values for plate roughly 1.6 – 40 mm thick, summarised from ASTM B928 and EN 485-2; limits fall in thicker plate. 5383 and 5059 are specified in EN 13195 and class-society rules, with higher minimums than 5083; the certificate states the values for the ordered thickness.
Physical properties (5083)
- Density
- 2.66 g/cm³
- Modulus of elasticity
- ≈ 71 GPa
- Thermal conductivity
- ≈ 117 – 120 W/m·K
- Coefficient of expansion
- ≈ 24 µm/m·°C
- Melting range
- ≈ 575 – 640 °C
- Magnetic
- Non-magnetic
H116, H321, H111 and H32: which temper?
H321
Strain-hardened and thermally stabilised, with the same corrosion test requirements. Equivalent in use to H116; mills offer one or both.
H111 / O
Annealed (H111 with slight strain hardening). Lower strength but best formability for curved plating, bow sections and pressed parts.
H32 / H34
Strain-hardened and stabilised general tempers. Fine for superstructure and interiors, but not corrosion-tested for immersed hull use unless the order says so.
H112
As-fabricated (hot-rolled) plate, common for thick plate and 5A-series grades; properties per the certificate.
T6 / T651 (6xxx)
Heat-treated condition for 6061 and 6082 plate and extrusions used in frames and fittings.
Standards and classification-society approval
| Document | What it covers |
|---|---|
| ASTM B928 / B928M | High-magnesium 5xxx sheet and plate for marine service; mandatory ASTM G66 (exfoliation) and G67 (mass-loss intergranular) testing |
| EN 13195 | Wrought and cast aluminium alloys for marine applications: specification of alloys, tempers and corrosion tests |
| ASTM B209 / EN 485 | General sheet and plate standards for non-hull or non-tested applications |
| DNV, ABS, LR, BV, RINA, ClassNK, KR | Rules for materials: approved manufacturers, tests witnessed or certified, and EN 10204 3.2 certificates for classed vessels |
For a classed vessel, the plate must come from a manufacturer approved by the relevant society and be certified accordingly, usually on an EN 10204 3.2 certificate countersigned by the surveyor. State the class society on the enquiry; it decides which mill sources are acceptable and how long certification takes.
Marine plate sizes and weights
Typical supply range
- Thickness
- Sheet from about 1.6 mm; hull plate commonly 3 – 25 mm; thicker plate to order
- Width
- 1,500, 2,000 and 2,500 mm are standard; wide plate reduces butt welds on large hulls
- Length
- 6,000 mm is common; up to about 12 m by agreement
- Imperial sizes
- 48 × 96, 48 × 120 and 60 × 120 in sheets
- Surface
- Mill finish, PVC-film protected one side; tread plate patterns for decks
5083 plate weighs 2.66 kg per m² per millimetre of thickness.
| Thickness (mm) | kg per m² | 2,000 × 6,000 mm plate (kg) | 2,500 × 6,000 mm plate (kg) |
|---|---|---|---|
| 3 | 8.0 | 96 | 120 |
| 4 | 10.6 | 128 | 160 |
| 5 | 13.3 | 160 | 200 |
| 6 | 16.0 | 192 | 239 |
| 8 | 21.3 | 255 | 319 |
| 10 | 26.6 | 319 | 399 |
| 12 | 31.9 | 383 | 479 |
| 15 | 39.9 | 479 | 599 |
| 20 | 53.2 | 638 | 798 |
| 25 | 66.5 | 798 | 998 |
Welding, forming and corrosion protection
Welding
MIG and TIG weld readily with ER5183 or ER5556 filler, which match the strength of 5083 and 5383; ER5356 is common on lower-strength grades. Never use 4xxx filler on high-Mg alloys, which risks brittle Mg2Si in the weld.
Friction stir welding
Widely used to make large flat deck and side panels from plate and extrusions with low distortion.
Forming
H116 plate bends cold with generous radii; for tight curvature use H111/O temper. Avoid hot forming in the sensitisation range.
Temperature limit
Keep alloys above ~3 % Mg away from sustained service above about 65 °C (engine rooms, exhaust areas); use 5454 or insulate.
Galvanic corrosion
Isolate aluminium from steel, copper and bronze fittings with insulating pads and sleeves; never use copper-based antifouling on aluminium hulls.
Cathodic protection
Aluminium or zinc sacrificial anodes protect immersed aluminium hulls; aluminium-alloy anodes are common and lighter.
Where each product goes on a vessel
- Bottom and side shell: 5083, 5383 or 5059 in H116/H321
- Decks and bulkheads: 5083 plate, friction-stir-welded panels, tread plate on working decks
- Superstructure and wheelhouse: 5083, 5754 or 5052 sheet and plate, often painted
- Frames, stiffeners and girders: 6082-T6 or 6061-T6 extrusions, or 5083 flat bar
- Tanks: 5083, 5086 or 5052 for fuel and water tanks
- Interiors: aluminium honeycomb and foam panels for light, fire-resistant partitions
- Offshore: helidecks, gangways and accommodation modules in 5083 plate and 6082 extrusions
References and standards
- ASTM B928/B928M – High Magnesium Aluminum-Alloy Sheet and Plate for Marine Service and Similar Environments
- EN 13195 – Aluminium and aluminium alloys: Wrought and cast products for marine applications
- ASTM G66 and G67 – Exfoliation (ASSET) and intergranular (NAMLT) corrosion tests for 5xxx alloys
- DNV Rules for Classification – Part 2: Materials and welding (aluminium alloys)
- The Aluminum Association – Aluminum: The Marine Metal / alloy designation data
Marine grade aluminium (aluminum) plate: FAQ
What is the best aluminium plate for boat hulls?
5083 in H116 or H321 is the standard choice. 5383 and 5059 offer higher strength for weight-critical high-speed and naval craft; 5086 is common in the US. Small boats often use 5052.
What does H116 mean on marine aluminium plate?
It is a strain-hardened temper processed and tested to resist exfoliation and intergranular corrosion under ASTM B928 or EN 13195, which makes it suitable for hull plating in seawater.
Is 6061 a marine grade aluminium?
6061 performs well above the waterline and is used for fittings, masts and frames, but it loses more strength when welded and is less resistant to seawater than 5xxx alloys, so it is not used for immersed hull plating.
Why should 5083 not be used above 65 °C?
Long exposure between about 65 and 200 °C can sensitise high-magnesium alloys, making them prone to intergranular corrosion. Use 5454 or insulate the plate in hot areas.
Do I need class certification for marine plate?
For vessels built under a classification society, yes: plate must come from an approved mill with certificates accepted by that society, usually EN 10204 3.2.
How much does a 2 × 6 m sheet of 10 mm 5083 weigh?
About 319 kg, at 2.66 kg per m² per millimetre of thickness.
Building or repairing an aluminium vessel?
Send the alloy, temper, thickness, sizes, quantity and class society. We will confirm availability, certification and a delivered price.
