Choosing Between 5083 H321 and 5083 H116 Aluminum Plate

When it comes to marine‑grade aluminum, 5083 H321 and 5083 H116 are two of the most widely used tempers. But what exactly sets them apart? Both are designed for harsh seawater environments and meet international standards like ASTM B928. However, they differ in processing, mechanical performance, and ideal applications. This article breaks down these differences to help you pick the right one.

*One quick note: we supply aluminum plates as raw materials and do not offer surface treatment or secondary processing services.*

Understanding “Temper” in Aluminum

“Temper” refers to the mechanical properties achieved through specific work‑hardening or heat‑treatment processes. In other words, two plates with the same 5083 designation can have very different hardness, strength, and corrosion resistance depending on their temper.

Common tempers for 5083 include O, H111, H112, H116, and H321. Among these, H116 and H321 are the two specifically developed for shipbuilding and offshore use. Both pass the required corrosion tests (ASTM G66 for exfoliation and ASTM G67 for intergranular corrosion).

Their chemical composition is identical – magnesium content ranges from 4.0% to 4.9%, and all other alloying elements are the same. The difference lies entirely in the production route.

Key Differences Between H116 and H321

Processing – one extra step

– 5083‑H116 is produced by cold working (strain hardening) only, with no subsequent heat treatment. It is designed for high‑magnesium 5xxx alloys and has strict requirements for corrosion resistance and mechanical properties.

– 5083‑H321 receives an additional stabilization heat treatment (low‑temperature annealing) after cold working. This step relieves residual stresses, improves dimensional stability, and enhances resistance to stress‑corrosion cracking.

Mechanical properties – largely the same

According to ASTM B928, for conventional thicknesses (3 mm to 40 mm), the mechanical values are very close:

> Keep in mind: when thickness exceeds 40 mm, the minimum tensile strength drops to 285 MPa and yield strength to 200 MPa for both tempers. Always check the specific gauge you need.

Corrosion resistance – different strengths

Both offer excellent seawater corrosion resistance and pass the ASTM G66 and G67 tests.

– H116 is specially formulated for high‑magnesium alloys and excels in resisting exfoliation corrosion.

– H321, thanks to its stabilization treatment, performs better against stress‑corrosion cracking, especially in welded areas.

Weldability – H321 is more stable

Both tempers can be welded easily using MIG, TIG, or other common methods.

The difference shows up after welding – because of the stabilization treatment, H321 retains better performance in the heat‑affected zone and has lower susceptibility to intergranular corrosion. For long weld seams or large welded structures, H321 is the safer bet.

Thermal stability – H321 handles temperature changes better

– H116 is suitable for continuous service temperatures up to 66°C.

– H321, with its stabilized microstructure, performs more consistently under cyclic loads and temperature variations.

How to Choose? A Simple Framework

Choose 5083‑H116 if:

– Your application involves hull shells, bottom plates, or decks that come into direct contact with seawater.

– You need thin to medium‑gauge sheets.

– You require top‑tier resistance to seawater corrosion and have relatively little welding.

Choose 5083‑H321 if:

– Your project includes extensive welding, especially long seams.

– You need thick plates (particularly above 40 mm).

– The structure will bear cyclic loads or temperature fluctuations.

– You are building superstructures, bulkheads, pressure vessels, or load‑bearing components.

Both tempers meet the approval requirements of major classification societies (CCS, ABS, BV, LR, etc.). So certification is not a deciding factor – the real criteria are application location, plate thickness, and fabrication method.

Other Factors to Consider

Thickness vs. performance – As mentioned, properties change for plates over 40 mm. Always request the certified test report for the exact thickness you plan to use.

Dimensions – Different projects require different widths, lengths, and gauges. We supply 5083 plates up to 2600 mm wide and 500 mm thick, with flexible sizing options.

Certification documents – For marine use, make sure the material comes with valid class society certificates. This is non‑negotiable for most shipyards.

Again, we only produce and supply bare aluminum plates – no surface coating, anodizing, or secondary cutting/fabrication is offered.

So, which one is right for you? H116 is the go‑to choice for hull plates and bottom shells that face constant seawater exposure. H321 is the better option for welded assemblies, thick sections, and load‑carrying parts. Ultimately, the decision between 5083 H321 and 5083 H116 comes down to your specific service conditions and fabrication needs. Check your thickness requirements, verify class rules, and match the temper to your welding workload – that’s the clearest path to a reliable, cost‑effective solution.

*Henan Mingtai Al supplies both 5083‑H116 and 5083‑H321 plates with full CCS, ABS, BV, and LR approvals, available in a wide range of dimensions to fit your project.*

FAQ

Q: Is the chemical composition of 5083‑H116 and 5083‑H321 the same?  

A: Yes – both contain 4.0–4.9% magnesium; the only difference is the processing route.

Q: Is H321 significantly more expensive than H116?  

A: The cost difference is usually small, as the extra stabilization step adds only marginal production time.

Q: Can both tempers be welded for ship hulls?  

A: Yes, but H321 provides better stability in the welded zone, especially for long seams.

Q: Which one should I choose if my plate is over 40 mm thick?  

A: Both have adjusted properties at that thickness, but H321 is more commonly used for heavy‑gauge welded structures. Check the actual test values for your specific gauge.