Marine grade 5083 H116 aluminium alloy plate pairs a high magnesium content with a strain-hardened temper that is stabilised against exfoliation corrosion, which is why it has become a default choice for hull scantlings, superstructures, decks and internal tanks in workboats, ferries, yachts and offshore units. This guide sets out the specification parameters, chemical composition, mechanical performance and inspection regime that a buyer should verify before certified marine plate is released for fabrication.
What 5083 H116 Marine Grade Aluminium Plate Is
5083 is an aluminium-magnesium alloy with magnesium in the 4.00-4.90% range and a small chromium addition. In the H116 temper the plate is cold worked to a controlled level and then held at an elevated temperature so that the beta phase is precipitated in a form that resists exfoliation and intergranular attack in marine atmospheres. Unlike the heat-treatable 6xxx and 7xxx families, 5083 strengthens through solid solution and strain hardening, so it keeps its corrosion resistance in the welded heat-affected zone and needs no post-weld heat treatment.
Plate is produced from homogenised ingot, hot rolled and then stress controlled. Wide plate up to 2600 mm is available, which reduces the number of longitudinal seams in a hull and therefore cuts both fabrication hours and the volume of weld inspection.
Specification Parameters
| Item | Value |
|---|---|
| Alloy | 5083 (Chinese designation LF4) |
| Temper | O, H111, H112, H116, H321 and H12-H38 as required; H116 for marine service |
| Thickness | 0.5-400 mm |
| Width | 100-2500 mm standard, wide plate up to 2600 mm |
| Length | 1000-12000 mm |
| Surface | Mill finish, free of oil stains, waves, scratches and roller marks, with neat edges and no burrs |
| Typical applications | Hull and deck plate, engine mounts, ship sides, bottom outer panels, tank and silo shells, LNG ceiling panels, power battery side panels |
Chemical Composition
The limits below follow the registered 5083 analysis. Nickel is not a specified addition in 5083, so it is deliberately omitted here; zinc and titanium are controlled as residuals.
| Element | Si | Fe | Cu | Mn | Mg | Cr | Zn | Ti |
|---|---|---|---|---|---|---|---|---|
| Limit (% mass) | 0.40 max | 0.40 max | 0.10 max | 0.40-1.00 | 4.00-4.90 | 0.05-0.25 | 0.25 max | 0.15 max |
Each other element is limited to 0.05% maximum and the total of other elements to 0.15% maximum.
Mechanical and Marine Performance
For H116 plate, ASTM B928 sets a minimum tensile strength of 275 MPa (40 ksi) and a minimum yield strength of 205 MPa (30 ksi), with elongation usually specified at 12% minimum in the as-supplied direction. Because the temper is non-heat-treatable, welded joints recover a large share of parent metal strength without re-solution treatment.
Density around 2.66 g/cm3, roughly one third that of steel, so a hull built in 5083 is far lighter than the equivalent steel structure.
Excellent resistance to seawater and industrial atmospheres; the surface forms a stable oxide film that limits general corrosion and pitting.
Good toughness at low temperature, which suits cold-service and LNG-related structures.
Very good weldability by MIG and TIG with 5183 or 5356 filler, and by friction stir welding.
Non-magnetic and spark-free behaviour, an advantage for hazardous-area equipment.
Why 5083 H116 Is Preferred Over Other Marine Materials
Against 5086, 5083 delivers slightly higher strength at comparable corrosion resistance, so scantlings can be reduced for the same design load. Against 6061, 5083 offers clearly better seawater corrosion resistance and weldability; 6061 is heat-treatable and can reach higher strength in some tempers, but its welded zone loses strength and it is less favoured for primary marine structure. Against steel, 5083 removes the need for cathodic protection and heavy coating systems, although absolute stiffness is lower, so deflection rather than stress often governs design and different joining techniques are required.
Quality Control and Certification for Classed Vessels
Certification of marine plate depends on a documented test programme rather than a single sheet of paper, and buyers should confirm the scope of every report issued:
Chemical analysis by optical emission spectrometry.
Tensile testing in both longitudinal and transverse directions.
Hardness testing as a supplementary check on temper uniformity.
Ultrasonic or radiographic examination for internal soundness on thicker plate.
Eddy current or dye penetrant examination for surface defects where specified.
Flattening and dimensional inspection, including flatness, squareness and thickness tolerance.
Salt spray testing is occasionally requested on coated samples; it supplements and never replaces real seawater exposure data. Results are normally issued with EN 10204 3.1 mill certificates, and 3.2 certificates are available when third-party witnessing is required. Where plate is intended for a classed vessel, the classification society rules for metallic materials govern the acceptance criteria, so the society and the required documentation package should be agreed before rolling rather than after delivery.
Handling, Storage and Safety
Store plate flat and fully supported to prevent bowing. Avoid prolonged contact with ferrous materials and with run-off from carbon steel, since both promote galvanic corrosion. Keep surfaces free of dirt and oil before finishing, and store under cover in dry conditions. Standard EHS precautions apply to aluminium dust generated during machining and to welding fume, including local extraction and suitable respiratory protection.
Ordering and Traceability Checklist
State grade 5083, temper H116, thickness, width, length and surface finish on the enquiry and on the order.
Confirm the classification society and the documentation package required for a classed hull.
Specify filler metal and welding procedure compatibility so that qualification testing is not duplicated.
Agree inspection level, sampling frequency and whether NDT records must travel with each plate.
Record heat number and plate identity against the mill certificate so that traceability survives cutting and forming.
FAQ
Q: Is 5083 H116 the same as 5083 H321?
Both are strain-hardened marine tempers with improved exfoliation resistance. H116 is the long-established temper for plate, while H321 applies to thinner material and reaches similar corrosion performance through a slightly different work-hardening route.
Q: Can 5083 H116 be welded without losing strength?
Yes. Welding with 5183 or 5356 filler produces joints that develop a large share of parent metal strength as the weld naturally ages, and no post-weld heat treatment is needed.
Q: What does DNV certification actually cover?
It covers the material test programme and the certificate package: chemical analysis, tensile testing in two directions, hardness, internal and surface inspection where required, plus dimensional checks, usually issued as EN 10204 3.1 or 3.2 documents.
Q: Why is 5083 preferred over 6061 for hull plate?
5083 resists seawater corrosion better, welds more predictably and keeps its properties in the heat-affected zone. 6061 is heat-treatable and can be stronger in some tempers, but strength loss after welding makes it a poorer choice for primary structure.
Q: How should 5083 plate be stored on site?
Flat, fully supported, dry and covered, and away from carbon steel contact or run-off. Galvanic contact and trapped moisture are the two main causes of surface staining before fabrication.
Q: Is salt spray testing a substitute for seawater exposure?
No. Salt spray is a rapid screening test for coated samples only; it cannot replace long-term seawater exposure data when corrosion performance is critical.
