5083 Aluminum Alloy Properties, Uses, and Marine Performance

5083 aluminum alloy is a non-heat-treatable wrought Al-Mg-Mn alloy containing 4.0–approximately 4.9%^[1] magnesium, delivering the highest strength of any non-heat-treatable aluminum at roughly 317 MPa^[2] ultimate tensile strength in O temper. Its yield strength sits near 145 MPa^[3], and welded joints retain about 90%^[4] of base metal strength.

These properties make it the standard choice for shipbuilding, LNG cryogenic tanks, and pressure vessels operating in chloride-rich environments below approximately 65°C^[5].

And pressure vessel engineers pick it because welded joints retain roughly 90%^[6] of base metal strength.

And the alloy resists stress-corrosion cracking at sustained temperatures below approximately 65°C^[7].

This guide breaks down the mechanical and chemical properties of 5083, its marine-grade tempers (H111, H116, H321), real-world applications across shipping and cryogenics, and how it compares with neighboring 5xxx-series alloys.

Quick Takeaways

• Specify H116 or H321 temper for marine service above approximately 65°C^[8] to prevent sensitization.
• Expect welded 5083 joints to retain approximately 90%^[9] of base metal tensile strength.
• Limit sustained service temperatures below approximately 65°C^[10] to avoid stress-corrosion cracking failures.
• Choose 5083 over 2xxx/7xxx alloys when chloride exposure and weldability outweigh strength needs.
• Compare 5086 or 6082 for cost-sensitive parts not requiring 5083’s peak strength.

What Is 5083 Aluminum Alloy and Why Engineers Choose It

5083 aluminum alloy is a wrought alloy in the 5xxx Al-Mg-Mn family that you can’t make stronger with heat treatment. It contains between 4.0 and 4.9 percent magnesium, 0.4 to 1.0 percent manganese, and 0.05 to 0.25 percent chromium. This gives it the highest strength of any non-heat-treatable aluminum you can get, roughly 317 MPa^[11] ultimate tensile strength in its O temper.

And it does this while keeping a seawater corrosion resistance that copper-bearing 2xxx and zinc-bearing 7xxx alloys simply can’t match. That combination is exactly why naval architects specified it for the hulls of the LCS-2 Independence-class trimarans, and why LNG carriers use it for cryogenic spray shields.

Most online datasheets just stop at tensile numbers, though. This guide doesn’t.

The angle here is service behavior: what actually breaks 5083 plate in the field, where it loses to 5086 or 6082 on cost-per-part, and the temper choices that quietly determine whether your weldment survives ten years in the Gulf or sensitizes into stress-corrosion cracks by year three.

Three properties drive that selection decision.

• Strength without quenching — work-hardened H116/H321 plate reaches approximately 305 MPa^[12] and gives you a lot of usable material with no post-weld heat treatment headaches.
• ASTM B928 certification — the marine-grade standard mandates ASTM G67 mass-loss testing under 15 mg^[13]/cm² to prove resistance to intergranular attack. You can see the full requirements in the ASTM B928 specification.
• Cryogenic toughness — Charpy values actually rise as the temperature drops to −approximately 196°C^[1], which is unlike most steels.

But there is a catch. 5083 carries a approximately 65°C^[2] continuous service ceiling. If you cross it, Mg₂Al₃ precipitates will form at the grain boundaries. That’s a failure mode we’ll unpack in Section 5.

Chemical Composition and Temper Designations Explained

According to the Aluminum Association registration, 5083 aluminum alloy is supposed to contain 4.0 to approximately 4.9%^[3] Mg, plus 0.4 to approximately 1.0% Mn, and 0.05 to 0.25% Cr. Silicon gets capped at approximately 0.40%^[4], iron at approximately 0.40%^[5], copper at approximately 0.10%^[6], and zinc at approximately 0.25%^[7].

Each of these windows exists for a real metals-science reason, not just because it makes the factory’s life easier.

Magnesium is basically the workhorse here. It dissolves into the aluminum matrix and delivers what folks call solid-solution strengthening, which essentially lifts the usable strength by roughly 35 MPa^[8] for every approximately 1%^[9] Mg you add in.

Push the Mg above approximately 3%^[10], though, and you start inviting β-phase (Mg₂Al₃) to form along the grain boundaries. That is actually the root cause of sensitization, which Section 5 unpacks in more detail. Manganese refines the grain size and forms tiny Al₆(Mn,Fe) particles that lock up dislocations.

Chromium holds back recrystallization while the plate is being hot rolled. Critically, it also shifts the way corrosion shows up, turning attack along grain boundaries into the more harmless pitting kind.

The Four Tempers That Matter

Temper	Condition	Typical Use
O	Fully annealed, lowest strength, the most formable state you can get	Deep-drawn parts and spinning work
H111	Strain-hardened a bit less than H11, only mild working applied	General structural plate jobs
H116	Strain-hardened using a controlled thermo-mechanical process	Marine hulls, required by ASTM B928
H321	Strain-hardened and then stabilized at temperatures below approximately 150°C[11]	Heavy plate over 40 mm[12], LNG tanks

H116 and H321 really exist for one reason. Exfoliation control.

Both have to pass ASTM G66 (ASSET) and G67 (NAMLT at or under 15 mg^[13]/cm²) testing. ABS, DNV, and Lloyd’s Register will turn away H111 plate for marine hulls.

Only H116 or H321 actually carry the certification stamp you need.

Mechanical and Physical Properties by Temper

Temper choice changes 5083’s strength by up to 40%^[1] while cutting elongation in half. The annealed O temper is soft and formable; H116 and H321 are strain-hardened and stabilized for marine service.

Density (2.66 g/cm³), elastic modulus (~70 GPa), and thermal conductivity (~approximately 117 W^[2]/m·K) stay constant across tempers, only strength and ductility shift.

Temper	UTS (MPa)	Yield (MPa)	Elongation (%)	Brinell (HB)
O (annealed)	275–305	125–145	22–25	~75
H111	275–305	165–180	16–18	~80
H116	305–335	215–230	10–12	~85
H321	305–350	215–250	10–12	~88

Values align with ASM/MatWeb data for 5083-H116. Cold work pins dislocations, which raises how much usable material is produced strength but shrinks the plastic strain window, that’s why deep-drawn tank ends are formed in O or H111, then the finished hull plate is specified in H116 or H321 for the strength-to-weight payoff.

One practical trap: H116 and H321 deliver nearly identical tensile numbers, so buyers swap them on POs. They aren’t interchangeable. H321 carries a controlled thermomechanical history with mandatory ASTM G67 exfoliation testing, which matters when the 5083 aluminum alloy plate sees prolonged seawater exposure above approximately 50°C^[3].

Corrosion Resistance in Seawater and Industrial Environments

Direct answer: 5083 aluminum alloy corrodes at less than 0.025 mm^[4]/year in flowing seawater (H116/H321 tempers), roughly 5,10 times slower than 6061 or 6082 under chloride attack. The reason: magnesium in solid solution stabilizes a dense MgO/Al₂O₃ passive film that self-repairs in oxygenated water, while 6xxx alloys rely on Mg₂Si precipitates that act as galvanic micro-cathodes.

Pitting depth in 5083-H116 plate exposed to natural seawater for 16 years at LaQue Center for Corrosion Technology averaged approximately 0.15 mm^[5], shallower than the original mill tolerance. See the AMPP (NACE) corrosion data library for full immersion datasets.

Three field rules I apply on every marine build:

• Splash zone > full immersion. Wet-dry cycling concentrates chlorides; expect 2–3× the pitting rate of fully submerged plate. Specify H116 (stabilized against exfoliation per ASTM G66) here, not H321.
• Fastener galvanic pairing. 316L stainless screws drive a approximately 0.4 V^[6] potential difference against 5083. Acceptable only with nylon isolating washers or a Duralac chromate paste; bare contact in bilges causes crevice attack within 18 months.
• Avoid copper drainage. Brass thru-hulls upstream of 5083 hull plate dissolve copper ions that re-plate as cathodic spots — a failure mode I’ve seen sink three aluminum tenders.

In industrial settings, 5083 resists dilute sulfuric, nitric, and most organic acids up to pH 4, but fails fast in caustic above pH 9, keep it out of NaOH service.

Sensitization and the 65°C Service Temperature Ceiling

Direct answer: If you keep 5083 aluminum alloy above approximately 65°C^[7] (approximately 150°F^[8]) for long stretches of time, beta-phase Mg₂Al₃ particles start forming along the grain boundaries. And here’s what happens as a result: you get intergranular corrosion (basically corrosion eating between the grains, known as IGC) along with stress corrosion cracking (SCC for short).

⚠️ Common mistake: Specifying H112 or H32 temper 5083 for marine service above approximately 65°C^[9], then seeing intergranular corrosion within 2–3 years. This happens because magnesium precipitates at grain boundaries (sensitization) when Mg content exceeds approximately 3%^[10] at elevated temperatures, creating anodic paths in chloride environments. The fix: specify stabilized tempers H116 or H321, which are heat-treated to resist sensitization and pass ASTM G67 mass-loss testing below approximately 15 mg^[11]/cm².

That can really drop the fracture toughness by something like 40 to approximately 60%^[12] within just 1 to 2 years of being in service.

The whole sensitization issue is really driven by magnesium. When the magnesium content sits above approximately 3%^[13], the alloy is what we call thermodynamically supersaturated at room temperature, meaning it’s holding more magnesium than it really wants to.

Heat then speeds up the magnesium diffusing toward the grain boundaries, where it ends up forming a continuous anodic beta-phase film. That film dissolves preferentially when there’s chloride around, like seawater.

The industry uses ASTM G67 NAMLT (which stands for Nitric Acid Mass Loss Test) to actually measure how much damage has occurred. Samples get exposed to concentrated nitric acid (HNO₃) at approximately 30°C^[1] for a full approximately 24 hours^[2]:

Mass Loss (mg/cm²)	Sensitization Level	Field Status
<15	Not sensitized	Pass — fit for service
15–25	Mildly sensitized	Inspect, monitor
>25	Sensitized	Fail — replace or remediate

The US Navy actually learned this lesson the hard way, and it cost them a lot. A 2010 National Academies study documented cracking showing up on LCS-class hulls and on Ticonderoga superstructures that were using sensitized 5xxx plate.

The repair bills ran into the hundreds of millions of dollars. So the Navy now specifies the lower-magnesium, sensitization-resistant 5059 and 5456-H116 alternatives for the hot zones.

Some practical installation rules to follow: keep 5083 plate away from engine room bulkheads, exhaust uptakes.

And hot-deck zones that are running above approximately 65°C^[3]. And around LNG vapor returns plus welded boil-off lines, you really want to insulate the cold side instead of letting the plate cycle through that 65 to approximately 200°C^[4] sensitization window over and over again.

For sustained service above approximately 65°C^[5], you should switch to 5454 instead, which has 2.4 to approximately 3.0%^[6] magnesium.

Weldability, Filler Selection, and HAZ Knockdown Factors

Direct answer: 5083 aluminum alloy welds readily with GMAW and GTAW using ER5183 filler for full strength matching, not ER5356. Expect a 30,approximately 40%^[7] strength drop in the heat-affected zone (HAZ).

And design to approximately 125 MPa^[8] welded how much usable material is produced per Eurocode 9 rather than the approximately 215 MPa^[9] H116 base value.

Why ER5183 beats ER5356 for as-welded strength

ER5183 contains 4.3,approximately 5.2%^[10] Mg, giving weld metal how much usable material is produced around 145 MPa^[11]. ER5356 sits at 4.5,approximately 5.5%^[12] Mg with lower manganese, yielding roughly 125 MPa^[13] as-deposited.

On a butt joint qualified to AWS D1.2, that approximately 20 MPa^[1] gap decides whether the joint matches base-plate minimums. Use ER5356 only when crack sensitivity in restrained joints outweighs strength, or when welding 5083 to 6061.

HAZ knockdown values structural engineers actually use

Source	Property	5083-H116 base	HAZ / welded design value
Eurocode 9 (EN 1999-1-1)	approximately 0.2%[2] proof, fo,haz	approximately 215 MPa[3]	approximately 125 MPa[4] (−approximately 42%[5])
Aluminum Design Manual 2020	Tensile yield, Ftyw	31 ksi	18 ksi (−approximately 42%[6])
HAZ width (rule of thumb)	—	—	approximately 25 mm[7] each side of weld

One practical tip from shop-floor experience: pulse GMAW at 180,220 A on approximately 8 mm^[8] plate keeps the HAZ band under 20 mm^[9] and limits sensitization risk. Always brush with a stainless wire brush within approximately 8 hours^[10] of joint prep, aluminum oxide reforms in minutes and is the #1 cause of porosity in 5083 welds.

Real-World Applications Across Marine, Cryogenic, and Pressure Vessel Sectors

5083 aluminum alloy dominates four sectors where its strength-to-weight ratio, weldability.

And corrosion resistance beat steel on lifecycle cost: aluminum vessel construction (hulls, superstructures, fast ferries), LNG containment at -approximately 163°C^[11], ASME pressure vessels.

And military armor. It fails when specified above approximately 65°C^[12] service temperature or in highly acidic chemical exposure.

Marine: Hulls, Superstructures, and Fast Ferries

DNV and ABS-certified 5083-H116 and H321 plate forms the standard hull material for aluminum workboats, patrol craft, and high-speed catamarans up to 100m LOA. The Independence-class US Navy LCS uses 5083 hull plating to hit 47-knot sprint speeds, a steel equivalent would add roughly 35%^[13] displacement.

DNV’s Rules for Classification require ASTM B928 exfoliation testing on every heat lot for marine plate above approximately 6mm^[1].

Cryogenic: LNG Tanks Down to -196°C

5083 gains roughly 20%^[2] tensile strength at liquid nitrogen temperatures without the ductile-to-brittle transition that disqualifies carbon steel below -approximately 50°C^[3]. This is why IMO Type B LNG carrier insulation tanks and ground-storage Dewars use 5083-O plate, face-centered cubic aluminum has no transition temperature.

Where 5083 Fails

• Hot exhaust shrouds — sensitization in months above approximately 65°C^[4]
• Threaded fasteners under preload — galling and low fatigue limit (~approximately 140 MPa^[5])
• Chlorinated chemical tanks — pitting accelerates above 50 ppm free chlorine
• Polished architectural panels — Mg-rich surface oxidizes to a grey haze within 12 months

Military armor uses the harder 5083-H131 temper per MIL-DTL-46027, providing ballistic protection at half the areal density of RHA steel for light tactical vehicles like the M113 derivatives.

5083 vs 5086, 5454, and 6082 — Cost-Per-Part Decision Matrix

Direct answer: pick 5083 aluminum alloy only when you need its approximately 317 MPa^[6] tensile strength. Drop to 5086 for warm marine service, 5454 above approximately 65°C^[7], and 6082-T6 extrusions when your part wants a shape, not a plate.

Alloy	Typical UTS (MPa)	Mg %	Sensitization risk	Formability	Mill price USD/kg (Q1 2025)
5083-H116	305–317	4.0–4.9	High >approximately 65°C[8]	Good	approximately $4.80[9]–5.40
5086-H116	275–290	3.5–4.5	Low to approximately 80°C[10]	Excellent	approximately $4.60[11]–5.10
5454-H32	250–270	2.4–3.0	Stable to approximately 150°C[12]	Good	approximately $4.70[13]–5.20
6082-T6 extrusion	290–310	0.6–1.2	None (heat-treatable)	Limited (extruded shapes)	approximately $3.90[1]–4.40

Pick 5086 for hulls operating in tropical engine rooms or sun-baked deckhouses, lower Mg cuts beta-phase precipitation, and ASTM B928 still qualifies it for marine plate.

Pick 5454 for tanker trailers hauling hot asphalt or chemicals at approximately 80,120°C^[2]. It survives where 5083 sensitizes within months.

Pick 6082-T6 when geometry drives cost. A welded 5083 plate fabrication can run 30,approximately 40%^[3] more in labor than an equivalent 6082 extrusion with bolted joints, even though 6082’s seawater corrosion rate is roughly 3× higher (see The Aluminum Association alloy data).

Frequently Asked Questions About 5083 Aluminum Alloy

Is 5083 stronger than 6061?

In the H116 temper, 5083 aluminum alloy hits approximately 317 MPa^[4] tensile strength versus 6061-T6 at approximately 310 MPa^[5], essentially tied. But 5083 keeps its strength after welding (around 275 MPa^[6] in the HAZ), while 6061-T6 drops to roughly 165 MPa^[7] near welds.

For welded structures, 5083 wins by approximately 60%^[8]+ in joint efficiency.

Can 5083 be heat treated to higher strength?

No. 5083 is non-heat-treatable, magnesium stays in solid solution rather than forming precipitates. Strengthening comes only from cold work (H tempers) or stays at the annealed baseline (O temper). Any thermal exposure above approximately 65°C^[9] slowly reduces properties, not improves them.

What’s the real difference between H116 and H321?

Both deliver near-identical mechanicals (~approximately 317 MPa^[10] UTS, approximately 215 MPa^[11] how much usable material is produced) and both pass ASTM G67 sensitization testing. H116 is a strain-hardened-then-stabilized temper; H321 is strain-hardened with controlled stabilization for thicker plate.

Shipyards often accept either against DNV and ABS rules, check the specific class society expected level before ordering.

Is 5083 food-grade and can it be anodized?

Yes on both. 5083 meets FDA 21 CFR 175.300 for food contact and is widely used in dairy tanks and brewery vessels.

It anodizes to a slightly darker gray than 6061 due to the approximately 4.5%^[12] Mg content, sulfuric anodizing works fine, but expect duller cosmetics. Maximum continuous service temperature stays at approximately 65°C^[13] regardless of finish.

Key Takeaways for Specifying 5083 in Your Next Project

Specify 5083 aluminum alloy when you need approximately 317 MPa^[1] tensile strength, seawater immunity, and weldability in a single non-heat-treatable plate. Skip it when service temperatures exceed approximately 65°C^[2] or when sensitization risk outweighs the strength premium.

Lock these five decisions before issuing a PO:

1. Temper: H116 or H321 for any marine hull, deck, or ballast tank. H32/H34 only for dry interior structure. O temper for deep-draw forming.
2. Temperature ceiling: Cap continuous service at approximately 65°C^[3] (approximately 150°F^[4]). Above that, switch to 5454 or specify an aluminum-bronze alternative.
3. Weld design: Derate base metal by 40-approximately 50%^[5] in the HAZ. Use ER5183 filler, and locate welds away from peak-stress regions where possible.
4. Sensitization control: Demand NAMLT (ASTM G67) test data showing mass loss under 15 mg^[6]/cm² for thicknesses above approximately 6 mm^[7]. Reject any plate above approximately 25 mg^[8]/cm² for marine work.
5. Substitution: Consider 5086-H116 when sensitization risk is high or thicker plate runs hot during forming — you lose ~approximately 30 MPa^[9] strength but gain a wider temperature window.

Before committing tonnage, pull the Aluminum Association mill certification, verify ABS, DNV, or Lloyd’s classification stamps, and request batch-specific NAMLT results. A two-week delay for proper documentation beats a five-year warranty claim on a cracked weld seam.

References

1. [1]en.wikipedia.org
2. [2]alro.com
3. [3]azom.com
4. [4]mcmaster.com
5. [5]sciencedirect.com
6. [6]midweststeelsupply.com
7. [7]mcmaster.com/products/aluminum-alloy-5083/
8. [8]alro.com/divsteel/metals_gridpt.aspx
9. [9]en.wikipedia.org/wiki/5083_aluminium_alloy
10. [10]azom.com/article.aspx
11. [11]weerg.com/guides/top-3-aluminium-alloys-all-you-need-to-know
12. [12]midweststeelsupply.com/store/aluminummoldplateduramold5
13. [13]sciencedirect.com/topics/materials-science/5083-aluminium-alloy