When engineers and shipbuilders specify marine grade aluminum, they are almost always referring to one alloy: 5083. No other wrought aluminum alloy combines the corrosion resistance, structural strength, weldability, and low-temperature performance that 5083 delivers in saltwater environments. It is the global standard for ship hull plating, the material of choice for LNG cargo tanks, and the specification demanded by classification societies from DNV and ABS to Lloyd’s Register and Bureau Veritas.
This guide covers everything procurement managers, naval architects, and fabricators need to know about 5083 marine grade aluminum sheet: its chemical composition and why each element matters, mechanical properties across all major tempers, the critical difference between H116 and H321, applications from commercial vessels to LNG carriers, classification society certification requirements, and a complete price and ordering guide.
5083 is an aluminum-magnesium alloy in the 5xxx series, containing 4.0 to 4.9% magnesium as its primary alloying element. It is the most widely specified marine grade aluminum alloy in the world, used wherever aluminum must perform in permanent or prolonged saltwater contact.
The alloy is not heat-treatable. Its strength comes from the solid-solution strengthening effect of magnesium in the aluminum matrix, enhanced by cold working in the H-series tempers. In the H116 temper — the standard specification for ship hull plating — 5083 delivers 275 to 350 MPa tensile strength and exceptional resistance to the exfoliation corrosion and stress-corrosion cracking (SCC) that are the primary failure mechanisms for aluminum in marine structural applications.
Three properties set 5083 apart from other aluminum alloys in marine service: its corrosion resistance in chloride environments is unmatched among common structural alloys; it welds reliably with ER5356 filler wire to near-parent-metal strength; and its mechanical properties actually improve at cryogenic temperatures down to −196°C, making it the standard material for LNG cargo tank construction.
Understanding the composition of 5083 explains why it performs so differently from other aluminum alloys in marine environments.
Element | Content (%) | Role | Why it matters |
Al | Remainder | Base metal | Provides light weight (2.66 g/cm³) and natural oxide film formation |
Mg | 4.0–4.9 | Primary strengthener | Higher Mg = stronger oxide film = superior saltwater corrosion resistance |
Mn | 0.4–1.0 | Grain refiner | Improves strength and weldability; reduces hot cracking tendency |
Cr | 0.05–0.25 | Grain stabilizer | Inhibits grain growth during welding; improves corrosion resistance |
Fe | ≤0.40 | Impurity | Strictly controlled — high Fe forms intermetallics that weaken corrosion film |
Si | ≤0.40 | Impurity | Strictly controlled — excess Si reduces toughness and corrosion resistance |
Cu | ≤0.10 | Impurity | Very tightly limited — copper severely reduces saltwater corrosion resistance |
Zn | ≤0.25 | Impurity | Controlled to prevent stress-corrosion cracking susceptibility |
Ti | ≤0.15 | Grain refiner | Small addition refines as-cast grain structure |
The composition design logic is clear: maximize magnesium for corrosion resistance and strength, add manganese and chromium for structural improvement, and severely restrict copper, iron, and silicon — the elements that most degrade performance in saltwater. The strict copper limit of 0.10% maximum is particularly significant: copper creates galvanic micro-cells at grain boundaries that accelerate pitting corrosion in chloride environments. This is why copper-containing alloys like 6061 and 7075 perform poorly in seawater compared to 5083.
The table below covers the complete range of 5083 tempers used in marine and structural applications. Values are per ASTM B209 and EN 485.
Temper | Tensile strength | Yield strength | Elongation | Brinell hardness |
H111 | 245 MPa (36 ksi) | 125 MPa (18 ksi) | 16% | ~65 HB |
H112 | 275 MPa (40 ksi) | 145 MPa (21 ksi) | 14% | ~70 HB |
H116 | 275–350 MPa (40–51 ksi) | 215–285 MPa (31–41 ksi) | 10–16% | ~75 HB |
H321 | 275–350 MPa (40–51 ksi) | 215–285 MPa (31–41 ksi) | 10–16% | ~75 HB |
H32 | 228–305 MPa | 180–255 MPa | 12–16% | ~70 HB |
O (anneal) | 270 MPa (39 ksi) | 115 MPa (17 ksi) | 22% | ~65 HB |
Several properties deserve particular attention. First, H116 and H321 deliver identical strength ranges despite being produced by different processes — this is by design, as both must meet the ASTM B928 requirements for marine hull plating. Second, the O (annealed) temper provides the best elongation at 22%, which is relevant for applications requiring significant forming before final assembly. Third, and most importantly for LNG applications: all 5083 tempers maintain or increase their strength at cryogenic temperatures. At −196°C, 5083-H116 tensile strength increases to approximately 380–420 MPa — higher than at room temperature — while elongation remains above 20%. This behavior is the opposite of most structural alloys, which become brittle at low temperatures.
The temper designation is as critical as the alloy number for marine applications. Specifying ‘5083’ without a temper is incomplete and can result in material that does not meet your project’s certification requirements.
H116 is the most widely specified temper for 5083 in structural marine applications. It is produced by controlled strain hardening to achieve a specific combination of strength and resistance to exfoliation corrosion and SCC. The H116 designation specifically indicates that the material has been processed to meet ASTM B928 — the standard for aluminum alloys in marine service — which includes resistance testing for exfoliation corrosion and SCC that standard H-series tempers do not require.
All major classification societies (DNV, ABS, Lloyd’s Register, Bureau Veritas, CCS) accept 5083-H116 for hull plating and primary structural applications. When a classification society certificate is required for a marine project, H116 is the default specification.
H321 is produced by a different process route than H116 — thermal stabilization rather than controlled deformation — but delivers the same strength range and meets the same ASTM B928 corrosion requirements. The two tempers are functionally equivalent in service. Some project specifications, particularly in naval shipbuilding, explicitly name H321 rather than H116 — in that case, H321 must be supplied even though H116 would perform identically.
For most commercial and industrial marine projects, either H116 or H321 is acceptable. If the project specification or classification society certificate does not name a specific temper, H116 is the standard default. If the specification names H321, supply H321 — do not substitute H116 without confirming acceptance with the classification society surveyor.
H32 (strain-hardened and stabilized) provides good mechanical properties and corrosion resistance suitable for marine atmosphere applications that do not require classification society certification. It is less expensive than H116 because it does not require the controlled processing and ASTM B928 testing. H32 is appropriate for non-structural marine components, marine-atmosphere exposed parts, and applications where the buyer’s quality system accepts mill certification without classification society endorsement.
H112 is the as-hot-rolled condition, producing the softest and most formable 5083 plate. It is used for thick structural plate applications where precise temper control is not required and some forming after delivery is expected. H111 is lightly cold-worked, providing slightly more strength than H112 while retaining good formability. Both are used in applications requiring post-delivery forming, such as curved hull plates that will be formed on a press before welding.
The corrosion resistance of 5083 in marine environments is its defining characteristic and the reason it is specified over stronger but less corrosion-resistant alloys.
When aluminum contacts air or water, it immediately forms a thin, self-healing aluminum oxide film (Al₂O₃) on its surface. This film is the primary corrosion barrier. Magnesium content strengthens and densifies this film: a 5083 alloy with 4.5% Mg produces a more robust, more continuous oxide film than a 5052 alloy with 2.5% Mg or a 6061 alloy with 1.0% Mg. The practical result is better resistance to pitting — the small, deep holes that form preferentially at film defects in chloride environments.
Exfoliation corrosion is a form of subsurface attack where layers of metal parallel to the surface delaminate and peel away, driven by the volume expansion of corrosion products forming along grain boundaries. It is particularly destructive in marine aluminum structures because it can proceed rapidly and is not easily detected until significant damage has occurred. The H116 and H321 tempers of 5083 are specifically engineered to resist exfoliation corrosion. ASTM B928 includes a standard exfoliation test (ASTM G66, the ASSET test) that H116 and H321 material must pass.
Stress-corrosion cracking (SCC) occurs when a susceptible material under sustained tensile stress is exposed to a corrosive environment, causing subcritical crack growth at stress levels far below the static yield strength. For aluminum alloys, the susceptibility to SCC increases with magnesium content — which creates a potential tension between 5083’s high-Mg composition and its SCC performance. The H116 and H321 temper solutions resolve this tension by controlling the distribution of the beta phase (Al₃Mg₂) at grain boundaries. In sensitized material (produced by incorrect temper or prolonged elevated-temperature exposure), the beta phase forms a continuous network at grain boundaries and creates a preferred SCC crack path. H116 and H321 processing prevents this sensitization.
5083 outperforms 5052 in seawater because its higher magnesium content produces a denser oxide film and greater resistance to pitting and exfoliation. 5052 is adequate for above-waterline marine applications and freshwater service; 5083 is required for hull plating and continuously immersed structures.
5083 outperforms 6061 in all marine environments because 6061’s copper and higher silicon content reduce its corrosion film integrity in chloride environments. 6061 corrodes significantly faster than 5083 in seawater immersion testing.
Component / use | Typical thickness | Temper | Reason for 5083 |
Ship hull bottom plating | 6–12 mm | H116 | Permanent seawater immersion, structural load |
Bulkheads | 6–10 mm | H116 / H321 | Pressure + seawater, SCC resistance required |
Longitudinal stringers | 8–15 mm | H116 | Primary structural load-bearing member |
Transoms | 8–20 mm | H116 | Hull closure, high stress zone |
Deck plating (commercial) | 5–8 mm | H116 / H321 | Saltwater deck wash, foot and cargo traffic |
LNG cargo tank walls | 10–100 mm | H116 / H321 | Cryogenic service at −196°C |
Offshore platform structure | 10–25 mm | H116 | Continuous marine atmosphere, structural |
Naval vessel superstructure | 4–8 mm | H116 | Weight-critical, extreme environment |
Aluminium patrol / fast craft | 3–6 mm | H116 | Lightweight hull, saltwater service |
Port and harbour infrastructure | 8–20 mm | H116 / H321 | Tidal zone, continuous salt exposure |
5083-H116 is the global industry standard for aluminum ship hull bottom plating and primary structural components in vessels where aluminum construction is specified. It is used in commercial ferries, fast vessels, patrol craft, research vessels, and pleasure yachts. For commercial vessels, hull plating in contact with seawater must be certified to classification society requirements — which means H116 or H321 with 3.1 or 3.2 mill test certificates.
The weight advantage of aluminum over steel — approximately one-third the density for similar structural performance in many applications — is the primary reason aluminum is chosen for vessel construction. For a 30-meter aluminum patrol boat, the weight saving compared to equivalent steel construction can exceed 15 tonnes, translating directly to higher payload, faster speed, or greater fuel efficiency.
5083 aluminum is the world standard for LNG (liquefied natural gas) cargo containment systems. LNG is stored and transported at −162°C, and the inner tank of an LNG carrier must maintain structural integrity and leak tightness at this temperature throughout a service life of 25 years or more.
The property that makes 5083 indispensable for this application is its cryogenic performance. Unlike most structural metals, which lose ductility and become brittle at low temperatures, 5083 gains strength at cryogenic temperatures while maintaining or improving elongation. At −196°C (liquid nitrogen temperature), 5083-H116 has higher tensile and yield strength than at room temperature, with elongation remaining above 20%. This combination of high strength and high ductility at extreme cold is extremely rare in structural materials.
LNG cargo tanks using 5083 aluminum are specified in the IMO’s International Gas Carrier Code and are used in membrane-type containment systems on large LNG carriers, small-scale LNG bunker vessels, and shore-based LNG storage tanks.
Offshore oil and gas platform topsides, helidecks, walkways, pipe supports, and equipment skids frequently use 5083-H116 plate and structural shapes. The combination of low maintenance requirements, resistance to the corrosive offshore atmosphere, and the weight savings compared to steel — which reduces structural loads on the platform jacket — make aluminum an increasingly preferred material for non-pressure-retaining offshore components.
5083 aluminum is a US Navy standard material for vessel superstructure, with the specific requirements covered under MIL-DTL-24767 and related specifications. The combination of low magnetic signature (important for mine countermeasures vessels), corrosion resistance, and structural performance makes 5083 the preferred aluminum alloy for naval applications.
5083 welds well by both MIG (GMAW) and TIG (GTAW) processes — a significant advantage over high-strength alloys like 6061 or 7075, which suffer more significant heat-affected zone (HAZ) strength reduction and have greater hot-cracking susceptibility.
The correct filler wire for welding 5083 is ER5356 (Al-5Mg) or ER5183 (Al-4.5Mg-0.7Mn). Both achieve weld metal tensile strength of 275 MPa or more when welding 5083 parent metal, satisfying the minimum joint efficiency requirements of classification society welding rules. ER5183 is preferred when maximum weld metal strength is required; ER5356 is more widely available and is acceptable for most structural marine welds.
Do not use ER4043 filler wire for structural 5083 welds. ER4043 (Al-5Si) produces a weaker weld joint with lower ductility that does not meet marine structural requirements, and its silicon content can create intermetallic compounds at the fusion boundary that are susceptible to corrosion in seawater.
The HAZ in 5083 welds is softer than the parent metal because the heat of welding anneals the cold-worked strengthening produced by the H-series temper. For H116 plate, HAZ tensile strength in the as-welded condition is approximately 240 to 270 MPa — still adequate for most structural calculations when the joint efficiency factor specified by the classification society is applied. Unlike heat-treatable alloys (6061, 7075), 5083 cannot be re-heat-treated to restore HAZ properties after welding.
Control heat input to minimize HAZ width. In production shipyard welding of 5083, this means using appropriate weld passes, allowing inter-pass cooling, and avoiding excessive preheat. For multi-pass welds on thick plate (over 15 mm), plan the pass sequence to distribute heat and minimize distortion.
Friction stir welding (FSW) is increasingly used for 5083 in commercial shipbuilding, particularly for large flat panel fabrication where distortion control is critical. FSW produces a weld with smaller HAZ than fusion welding, better flatness, and higher retained strength (typically 280–310 MPa, compared to 240–270 MPa for MIG). Panels for high-speed ferries and large naval vessels are among the applications where FSW of 5083 has been commercially implemented.
For commercial shipbuilding, offshore construction, and naval applications, material certification is not optional. Classification society certification of the 5083 material is required by flag state regulations and is a condition of vessel insurance. Here is what you need to know.
When a supplier says material is ‘DNV certified’ or ‘ABS approved’, it means the rolling mill has been audited and approved by the classification society to produce marine grade aluminum, and the specific batch of material has been tested in accordance with the society’s rules and certified by a society surveyor. The mill test certificate (MTC) bears the society’s stamp, providing a documented chain of custody from the smelting heat to the delivered plate.
• DNV (Det Norske Veritas, Norway): dominant in Norwegian-flagged vessels, offshore, and European shipping
• ABS (American Bureau of Shipping): required for US-flagged vessels and Gulf of Mexico offshore
• Lloyd’s Register (LR): widely used in UK-flagged and international commercial shipping
• Bureau Veritas (BV): common for French-flagged and West African operations
• CCS (China Classification Society): required for China-registered vessels and Chinese shipyard production
For certified marine aluminum sheet, request the following from your supplier at time of order:
• Mill Test Certificate (MTC) 3.1 or 3.2: documents the chemical composition and mechanical test results for the specific lot of material. Type 3.1 is certified by the mill’s own authorized inspector; Type 3.2 requires an independent third-party inspector (required by some classification societies for critical structural applications).
• Classification society endorsement: the MTC must carry the surveyor’s stamp from the relevant society. Confirm with your supplier which societies they are approved to supply under before placing the order.
• Alloy and temper confirmation: the MTC must explicitly state 5083-H116 or 5083-H321 — not simply ‘5083’. The temper must be documented to confirm ASTM B928 compliance.
• Certificate of Conformance (CoC): supplier’s written declaration that the material meets the specified standard, typically provided alongside the MTC.
Industrial grade 5083 without classification society certification is available at a lower cost. It is appropriate for applications that do not require certification: processing equipment, non-marine structural use, and marine atmosphere applications where the buyer’s quality system does not require society certification. Never substitute uncertified material for certified in applications where classification society documentation is required — the vessel’s insurance coverage and regulatory compliance depend on having the correct documentation.
5083 is priced at a premium over general-purpose alloys like 3003 and 5052, reflecting its higher magnesium content, more demanding process controls, and the cost of classification society testing and certification for marine-grade material.
5083-H116 is typically priced similarly to 6061-T6 or slightly higher, depending on market conditions. It commands a premium of approximately 15 to 30% over 5052-H32 for the same thickness and width. The main premium drivers are: higher magnesium content (Mg is more expensive per tonne than the silicon and manganese used in other alloys at comparable levels), the controlled H116 temper processing and ASTM B928 testing, and the classification society certification cost when applicable.
Classification society certified 5083-H116 with 3.1 MTC documentation typically costs 10 to 20% more than commercial-grade 5083 of the same temper and dimensions. This premium reflects the mill’s cost of maintaining classification society approval, the surveyors’ inspection fees, and the additional testing required for each certified lot. For projects where certification is required, this premium is non-negotiable — the alternative is a vessel that cannot be registered, insured, or operated commercially.
Thin 5083 sheet (under 3 mm) carries a higher per-kilogram price than standard plate thicknesses (6–20 mm) because of the additional cold-rolling processing required for thin gauges. For hull plating, which typically ranges from 5 mm to 15 mm, pricing is at the most economical point of the gauge range.
A common and costly procurement error is ordering H32 instead of H116 to save approximately 10 to 15% on material cost. If the project requires classification society certification, H32 material will be rejected during survey because it does not meet ASTM B928 exfoliation and SCC requirements. The cost of material rejection, procurement of replacement certified material, and the associated construction delays far exceeds the original saving. Always specify H116 or H321 for classification society applications.
5083 marine grade aluminum sheet is available from 1.5 mm (thin sheet for interior and lightweight structural applications) to over 200 mm (heavy structural plate for large vessels and offshore infrastructure). Common marine hull plating thicknesses run from 4 mm for small aluminium craft to 20 mm for large commercial vessels, with most work concentrated in the 5 to 12 mm range.
Standard mill widths are 1000 mm, 1219 mm, 1500 mm, 2000 mm, and 2500 mm. Wider plates (up to 3500 mm) are available from mills with heavy-rolling capability and are used in shipbuilding to minimize the number of longitudinal weld seams in hull plating — each seam represents a potential leak path and an additional inspection requirement. Standard lengths are 2000 mm, 2438 mm, 3000 mm, and 6000 mm; longer lengths can be ordered for projects where minimizing transverse seams is a design priority.
Each delivery of certified 5083 marine aluminum sheet must be accompanied by an MTC that documents: the alloy (5083), the temper (H116 or H321), the heat (lot) number, the chemical analysis for all specified elements, the tensile test results (tensile strength, yield strength, elongation) from the specific lot, the hardness test results, and the classification society stamp and surveyor signature. Retain MTCs for the life of the vessel — they may be required for re-certification surveys, insurance claims, or vessel sale documentation.
A complete specification in your inquiry prevents delays and ensures you receive material that meets your project requirements. Include all of the following:
• Alloy: 5083 (always specify the full alloy number)
• Temper: H116 or H321 for classification society applications; H32 for non-certified marine use
• Thickness in mm: confirm the exact design thickness, accounting for any forming allowance
• Width in mm: specify standard or custom width
• Length in mm: standard or custom length; confirm whether cut-to-length service is required
• Quantity: in kilograms or metric tonnes; confirm whether split shipments are acceptable
• Certification required: state which classification society (DNV, ABS, LR, BV, CCS) and whether 3.1 or 3.2 MTC is required
• Trade terms: FOB, CIF, or DDP; specify destination port for CIF/DDP
• Delivery date: required completion date to allow production and logistics planning
• Special requirements: surface protection, marking requirements, packing instructions for sea freight
We supply 5083 marine grade aluminum sheet and plate to shipyards, offshore fabricators, and marine equipment manufacturers worldwide.
• Full temper range: H116, H321, H32, H112, H111 — all standard marine tempers stocked and available to order
• Thickness coverage: 1.5 mm sheet through 200 mm heavy plate
• Classification society certification: DNV, ABS, LR, BV, and CCS certified material available with 3.1 and 3.2 MTC documentation
• Custom dimensions: specify your exact thickness, width, and length and we cut to order with accurate dimensions
• LNG-grade material: cryogenic testing documentation available for LNG containment applications
• Export experience: established supply relationships with shipyards and marine fabricators across Southeast Asia, the Middle East, Europe, and the Americas
• Fast RFQ response: provide alloy, temper, thickness, width, length, quantity, certification requirements, and trade terms — we reply within 24 hours with pricing and availability
Contact us today with your specification. Whether you are building a new vessel, repairing hull plating, or fabricating LNG storage equipment, we have the material and documentation to support your project.
