What is the difference between 5083 H116 and 5083 H321 aluminum?
Both 5083-H116 and 5083-H321 are high-magnesium, marine-grade aluminum plates designed for shipbuilding. They share identical chemical compositions and mechanical limits. The only difference lies in their manufacturing processes: H116 achieves its stability through specific strain hardening for Al-Mg alloys, while H321 achieves it through strain hardening followed by low-temperature thermal stabilization. Functionally, both provide supreme resistance to exfoliation corrosion in severe seawater environments.
As a specialized supplier of marine-grade aluminum, our engineering team at GNEE frequently receives inquiries from shipyard procurement managers asking: "Should I specify 5083-H116 or 5083-H321 for my vessel's hull?"
There is a widespread misconception in the industry that one temper offers significantly better corrosion resistance than the other. This is metallurgically incorrect. If you are building passenger ferries, offshore platforms, or patrol boats, specifying the right material requires understanding exactly how these tempers behave under international maritime standards.
This guide breaks down the technical processing, mechanical properties, and procurement standards for both tempers, ensuring you source the correct, class-certified material for your next maritime project.
Contact GNEE Today to Buy DNV Certified 5083 H116/H321 Aluminum Plates
5083-H116 Strain Hardened vs 5083-H321 Stabilized Aluminum
To understand the difference, we must first look at the metallurgical challenge of the 5000-series Aluminum-Magnesium (Al-Mg) alloys.
EN 5083 contains over 4.0% Magnesium. Over time, especially when exposed to elevated temperatures and continuous saltwater, high-magnesium alloys can suffer from "sensitization." Magnesium atoms migrate to the grain boundaries, forming a continuous network of beta phase (Mg₂Al₃). This makes the metal highly susceptible to severe intergranular corrosion and exfoliation corrosion (where the metal flakes apart).
Both H116 and H321 tempers were invented specifically to solve this problem, but they take different manufacturing routes:
- 5083-H116 Temper: This temper applies specifically to 5xxx series alloys with nominal magnesium content of 3.0% or more. The aluminum plate is strain-hardened (cold-worked) to reach specific tensile strength limits. More importantly, the temperature is carefully controlled during the final rolling operations to lock the magnesium structure in place, rendering it immune to exfoliation without requiring subsequent thermal baking.
- 5083-H321 Temper: To achieve the H321 temper, the 5083 aluminum plate is first strain-hardened to a specific strength. After rolling, it is subjected to a low-temperature thermal treatment (stabilization). This mild heating process slightly softens the metal to prevent age-softening over time and stabilizes the metallurgical structure against grain boundary precipitation.
The Engineering Verdict: Despite the different processing routes, both tempers end up at the exact same destination. Both are completely stabilized against exfoliation corrosion for continuous service at temperatures up to 150°F (66°C).
Chemical and Mechanical Properties of EN 5083 H116 & 5083 H321 Alloy Sheets
In practical shipyard applications, naval architects treat H116 and H321 as interchangeable. Below are the verified chemical limits and mechanical properties for GNEE's marine plates, demonstrating that their structural performance is identical.
5083 Aluminum Alloy Typical Chemical Composition (Weight %):
| Alloy | Mg | Mn | Cr | Si | Fe | Zn | Al |
|---|---|---|---|---|---|---|---|
| 5083 | 4.0 - 4.9 | 0.4 - 1.0 | 0.05 - 0.25 | ≤ 0.40 | ≤ 0.40 | ≤ 0.25 | Remainder |
5083 Aluminum Alloy Mechanical Properties (Minimum Values for Standard Hull Plate Thicknesses):
| Temper Grade | Tensile Strength (Rm) | Yield Strength (Rp0.2) | Elongation (%) | Corrosion Resistance |
|---|---|---|---|---|
| 5083-H116 | ≥ 305 MPa | ≥ 215 MPa | ≥ 10% | Supreme (Passes ASTM G66/G67) |
| 5083-H321 | ≥ 305 MPa | ≥ 215 MPa | ≥ 10% | Supreme (Passes ASTM G66/G67) |
ASTM B928 vs ASTM B209: Standards for 5083 H116 and H321 Shipbuilding Aluminum
A fatal mistake many buyers make is procuring standard ASTM B209 commercial plates for marine applications.
- ASTM B209M: This is the standard specification for general commercial aluminum sheet and plate. It tests for basic mechanical properties.
- ASTM B928M: This is the critical standard for High Magnesium Aluminum-Alloy Plate for Marine Service.
If you order ASTM B928 marine aluminum plate specifications from GNEE, it means the 5083-H116 or H321 plates have successfully passed rigorous accelerated corrosion tests. Specifically, they pass the ASTM G66 ASSET Test (ensuring no exfoliation corrosion) and the ASTM G67 NAMLT Test (ensuring minimal intergranular mass loss). Both H116 and H321 must pass these exact same tests to be certified for maritime use.
Practical Applications of 5083-H116 and 5083-H321 Marine Grade Aluminum in Shipyards
Because of their lightweight nature, high yield strength, and excellent post-weld integrity (using ER5183 or ER5356 welding wire), these plates dominate the high-performance marine sector. Common applications include:
- Below-Waterline Hulls: The stabilization of both tempers ensures long-term integrity against continuous seawater exposure.
- Automobile Tanker Bodies & LNG Storage: The cryogenic stability of 5083 means it performs exceptionally well in low-temperature liquid natural gas transport without becoming brittle.
- Offshore Platforms & Deck Structures: Providing a high strength-to-weight ratio, allowing for larger payloads on commercial vessels.
GNEE Supply Capabilities for DNV/ABS Certified 5083-H116 / 5083-H321 Plates
Do not risk your vessel's structural integrity on uncertified metals. Sourcing reliable marine aluminum requires complete metallurgical traceability.
As a direct 5083 H321 shipbuilding aluminum supplier, GNEE manufactures precision plates optimized for shipyard fabrication.
- Classification Society Approvals: We can supply materials certified by DNV, ABS, KR, LR, CCS, and BV.
- Wide Format Plates: We offer large-format plates (e.g., 2000mm x 8000mm) to significantly reduce welding seams on boat hulls, minimizing thermal distortion and saving fabrication labor.
- Full Traceability: Every shipment is accompanied by a Mill Test Certificate (MTC) 3.1/3.2 detailing the chemical composition and corrosion test results.
Ensure your next vessel passes class inspection with premium marine aluminum.
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