Strength in numbers

Aluminium Alloy   |   Commercial Alloy

Transition Joint


Triplate is widely used for the on–site welding of aluminium to steel, for example ships hulls to decks and oil rig superstructures to steel supports.

It consists of a steel base material and a corrosion resistant marine-grade aluminium alloy top layer with an intermediate layer of pure Aluminium to promote bonding.

The three Triplate layers are homogeneously bonded together by vacuum-explosion welding.

Using Triplate

During processing the temperature of the material MUST NOT be allowed to exceed 315 Centigrade. 


DO NOT pre-heat the transition joint before welding.


Welding methods to be used are similar to those for the parent metals.


Ideally the aluminium weld should be made first after removal of the aluminium oxide film by wire-brushing, followed by de-greasing.  Argon shielding gas is recommended.  Small diameter wires are recommended (1.2mm).  Welding methods include GTAW, GMAW, TIG, MIG and Synergic pulse MIG.


The steel weld is made using a coated electrode and GMAW, SMAW or FCAW.  Small diameter electrodes are recommended (2.5mm).


When bending ensure that the minimum bend radius is at least ten times the strip width or thickness.

Mechanical Properties

Shear Strength – Basemetal/Intelayer: > 55N/mm2


Tensile Strength (through thickness): > 75N/mm2

Chemical Composition

Base Material: Steel LRS Ship-Plate Grade A or St 52-/3N


Interlayer: 99.5% Pure Aluminium – Alloy 1050A


Superlayer: Aluminium Alloy 5083 (AlMg4.5Mn)


Width:  25mm

Thickness:  34/35mm

Lengths:  3800mm

Specification / Approvals

Triplate meets MIL-J-24445A and is approved by Lloyd’s Register of Shipping.