When marine engineers and purchasing managers source heavy-duty aluminum for shipbuilding or offshore structures, they almost always select Aluminum Alloy 5083. However, a common technical roadblock arises on the purchase order: Should you choose aluminum plate 5083 H116 vs 5083 H321?
Both tempers are manufactured from the exact same 5083 aluminum-magnesium alloy block. They share the same chemical composition, offer extreme strength, and are highly resistant to seawater and industrial chemicals. The difference lies entirely in how the metal is processed at the mill-specifically, the "temper" route.
At GNEE, a leading 5083 aluminum plate manufacturer, we will break down the real technical differences, debunk common corrosion myths, and help you select the right plate for your specific project.
1. Aluminum Plate 5083 H116 / 5083 H321 Chemical Composition (%):
Because both plates belong to the 5083 alloy family, their chemical makeup is strictly identical. They rely on high Magnesium (Mg) content for strength and traces of Manganese (Mn) and Chromium (Cr) to lock the grain structure against cracking.
| Element | Composition % |
| Al | REM |
| Si | ≤0.4 |
| Cu | ≤0.10 |
| Mg | 4.0-4.9 |
| Zn | ≤0.25 |
| Mn | 0.40-1.0 |
| Ti | ≤0.15 |
| Cr | 0.05-0.25 |
| Fe | ≤0.40 |
| Note: Single ≤ 0.05; Total ≤ 0.15 | |
2. The Core Difference: Processing and Tempering Routes
If the chemicals are the same, why do we have two different designations? It is about how the metal is rolled and treated to prevent corrosion in saltwater. 5xxx series alloys with over 3% magnesium are prone to losing stability over time if not processed correctly.
What is 5083-H116 flat aluminum plate?
The H116 temper means the product is heavily strain-hardened during the final rolling operation to reach specified tensile property limits. It does not undergo subsequent thermal baking. Instead, the mill process is tightly controlled to ensure it inherently meets strict corrosion-resistance levels.
What is 5083-H321 flat aluminum plate?
To achieve the H321 temper, the aluminum plate is first strain-hardened (rolled), and then it is subjected to a low-temperature thermal treatment called "stabilizing." This baking process slightly softens the metal just enough to lock its mechanical properties, ensuring it does not naturally soften further over decades of use.
3. Mechanical properties of 5083 alloy aluminum plate
| Property | 5083-H116 Aluminum Plate | 5083-H321 Aluminum Plate |
|---|---|---|
| Ultimate Tensile Strength | ≥ 305 MPa | 305 – 358 MPa |
| Yield Strength | ≥ 215 MPa | ≥ 215 MPa |
| Elongation | ≥ 10% | ≥ 10% |
Key Insight of 5083 alloy aluminum plate
| Aspect | Comparison Result |
|---|---|
| Tensile Strength | H321 slightly higher upper range |
| Yield Strength | Essentially the same |
| Elongation | Essentially the same |
| Engineering Performance | No significant difference in most applications |
| Selection Basis | Certification requirements & corrosion resistance |
4. Debunking the Corrosion Myth: ASTM B928 Standard
You may read outdated information claiming that 5083 H321 has "better" corrosion resistance than H116. This is technically incorrect for modern aluminum manufacturing.
When you buy 5083 H116 aluminum sheet or H321 from a certified mill like GNEE, both must pass the exact same rigorous marine standards outlined in ASTM B928M (Standard Specification for High Magnesium Aluminum-Alloy Sheet and Plate for Marine Service).
Both tempers are guaranteed to pass:
- ASTM G66 (ASSET Test): Proves resistance to exfoliation corrosion (flaking/peeling in saltwater).
- ASTM G67 (NAMLT Test): Proves resistance to intergranular corrosion (micro-cracking between metal grains).
Both offer equivalent, top-tier protection in marine environments. The choice between them usually comes down to legacy shipyard blueprints or specific classification society (DNV, ABS, LR) preferences in your region.
5. The Critical Warning: The 150°F (66°C) Temperature Limit
Whether you use marine grade aluminum 5083 H321 or H116, there is one absolute engineering rule: Do not use them in continuous service environments above 150°F (66°C).
Why? Prolonged exposure to heat causes "sensitization." The magnesium atoms migrate and precipitate at the grain boundaries. If exposed to seawater afterward, the plate will suffer sudden, catastrophic intergranular cracking. If your project involves high-heat engine rooms or hot pressure vessels, contact GNEE to discuss alternative alloys like 5454 aluminum alloy.
6. Applications: Where to Use 5083 H116 and H321 aluminum plate?
- Shipbuilding: Both are the global standard for hull plates, bulkheads, and decks on fast ferries, naval vessels, and yachts.
- Cryogenic & Pressure Vessels: Both perform exceptionally well in extremely cold environments, making them ideal for LNG (Liquefied Natural Gas) storage tanks.
- Heavy Transportation: Used in severe-duty dump truck beds and railway tank cars where high impact and corrosion resistance are required. (Note: For standard bus body panels, commercial 5052 or standard 5083-O is more cost-effective than the premium marine B928 tempers).
Why Source Your Marine Aluminum from GNEE?
Using substandard aluminum in marine applications leads to failed inspections and millions in rework costs. GNEE guarantees the integrity of every plate.
- Certified Quality: We provide strict EN 10204 3.1 or 3.2 Mill Test Certificates verifying that ASTM B928, G66, and G67 tests were passed.
- Class Approvals: Plates certified by DNV, ABS, CCS, or LR are available upon request.
- Custom Cutting: We supply ultra-wide and thick plates to reduce your welding seams and construction time.
Get Your Accurate Quote and Engineering Data
Do you need an exact 5083 h321 marine aluminum price for your current bill of materials? Stop guessing which temper is locally available.
Contact GNEE today. Send us your required thickness, temper, dimensions, and quantity.
Mention this article in your inquiry, and our engineering team will send you our exclusive "2026 Marine Alloy Temper Selection Matrix" and a free material data sheet to help you optimize your procurement process!
