Strength in numbers

Aluminium Alloy   |   BS-L

L81 H16 or H26 Sheet

Commercial5251 - Obsolete

Nameplates, traffic (road) signs, architectural paneling. Welded tubes, chemical industry, irrigation. Offshore applications, welded structures. Pressure vessels, boilermaking.

Characteristic Properties:
Very good corrosion resistance to seawater and marine and industrial atmosphere. Very good weldability. Medium to high strength alloy for sheet products slightly lower than 5086. Medium high fatigue strength. Good cold formability.

Chemical Composition

BS 3L81(1985)
Alloy L81
Chemical Element % Present
Aluminium (Al) balance
Other (Each) 0.05 max
Others (Total) 0.15 max
Titanium (Ti) 0.15 max
Chromium (Cr) 0.15 max
Copper (Cu) 0.15 max
Zinc (Zn) 0.15 max
Silicon (Si) 0.4 max
Iron (Fe) 0.5 max
Manganese (Mn) 0.1 - 0.5
Magnesium (Mg) 1.7 - 2.4

The material shall be supplied cold rolled (H16) or cold rolled and partially annelaed (H26).

Alloy Designations

Aluminium alloy BS L81 - 5251 is covered by standard BS EN 3L81 (1985)

Temper Types

The most common tempers for L81 - 5251 aluminium are:

  • H16
  • H26

Supplied Forms

L81 - 5251 is supplied in the following forms:

  • Sheet
  • Strip

Generic Physical Properties

Physical Property Value
Density 2.69 g/cm³
Melting Point 650 °C
Thermal Expansion 23.6 x10^-6 /K
Modulus of Elasticity 70.0 GPa
Thermal Conductivity 149 W/m.K
Electrical Resistivity 37.5 % IACS

Mechanical Properties

BS 3L81(1985)
Sheet - 0.4mm to 0.8mm
Mechanical Property Value
Tensile Strength 225 Min - 275 Max N/mm2
0.2% Proof Stress 175 Min N/mm2
Elongation A50 mm 3 Min %

Mechanical properties relate to material with a nominal thickness of 0.4mm up to and including 0.8mm. The specification contains other values for different material thicknesses.