GRADE GUIDE · 5083
Aluminium 5083 (AlMg4.5Mn) is the shipbuilding plate alloy: the strongest of the common non-heat-treatable grades, holding its properties after welding and resisting seawater so well that hulls, superstructures and LNG tanks are built from it. The H116 temper is the marine standard.
Also listed as: AlMg4.5Mn · EN AW-5083 · A95083 · 3.3547
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Push the magnesium to 4.5% with a manganese addition and you get the 5xxx series at full strength — around 215 MPa yield in H116 — while keeping the series' signature virtues: weldability without cracking, no strength collapse in the heat-affected zone beyond the cold-work loss, and excellent salt-water resistance. Boat builders across the Gulf run on this plate; it is also the alloy of cryogenic tanks, since it toughens rather than embrittles at LNG temperatures.
H116 and H321 tempers carry marine certification against intergranular attack — for hull work, look for the temper and class society stamp on the certificate. Off-cuts arrive as plate drops from boat and tank builders in useful thicknesses; forming is stiffer than 5052, so plan generous bend radii.
The combination nothing else matches at the price: highest weldable-marine strength, certified resistance to seawater intergranular attack in H116 temper, and full toughness retained after welding. Class societies write it into their rules directly.
Yes — like all aluminium it has no brittle transition, and 5083 actually gains strength and toughness as it cools, which is why LNG containment systems use it.
It is stronger and correspondingly stiffer to form — wider bend radii, more press tonnage. For heavy plate and welded structure take 5083; for tight-bend sheet work 5052 remains the kinder metal.