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Steels coated with Alusi®, an aluminium-silicon alloy


Alusi®  coating is able to withstand heat and high-temperature oxidation as well as being highly corrosion-resistant and highly reflective, making it suitable for applications in a corrosive atmosphere subject to high temperatures.

Thanks to these various properties, Alusi® can be widely used, enabling a reduction in overall operating costs to be achieved when used as a substitute for more costly materials. Its high level of reflectivity makes it an ideal coating for thermal insulation applications.


  • Insulating heat shields
  • Engine heat shields
  • Exhaust systems
  • Fuel tanks
  • Biodiesel filters
  • Housings/crankcases
  • Underbody parts

Exhaust systems

Alusi® coating withstands temperatures of up to 650 °C, even 800 °C (DX55D+AS steel) without scaling or delamination and exhibits excellent corrosion resistance. For these reasons it is widely used in exhaust systems.

There is an Alusi® grade meeting in-service performance requirements for every major exhaust system component.

  Primary downpipe Catalytic converter
Particle Filter
Catalytic converter/
muffler connection
Front muffler/
intermediate pipe
Rear muffler
Temperature 400 - 750°C 400 - 750°C 200 - 500°C 250 - 500°C Internal: 400 -110°C
External: 50 - 300°C
Aggression Hot gas,
salt, mud
Hot gas, salt, mud Hot gas, salt, mud Hot gas, salt, mud Internal: condensates
External: atmosphere, salt, mud
Grade DX55D+AS DX55D+AS DX55D+AS DX55D+AS Internal casing:
ArcelorMittal 53+AS
External casing:
ArcelorMittal 54+AS
ArcelorMittal 51+AS - ArcelorMittal 52+AS

A coating weight of 150 g/m² and the use of EasyfilmTM can further increase corrosion resistance in exhaust system applications

The DX55D+AS grade, specifically developed to guarantee coating integrity up to 800 °C and to withstand high-temperature oxidation, is recommended for parts upstream of the front silencer.

  • Corrosion resistance comparison: Galvanised/galfan/Alusi® in salt spray

  • High temperature cyclic oxidation comparison

Secondary processing - Welding

Most welding techniques (spot, seam, high frequency) and MIG, MAG and TIG processes are applicable to Alusi® without special equipment.

Heat shields

Excellent reflectivity, ability to withstand high temperatures and corrosion resistance, enable the Alusi® coating to be used in engine heat shield and underbody heat shield applications.

Its mechanical properties, including at high temperatures, enable the Alusi® coating to be recommended for use in very thin coating layers, thus offering material cost reduction relative to competitive systems.

Reflectivity - Thermal insulation

Alusi® coating offers excellent thermal insulation properties due to its high reflectivity.

Its aluminised surface reflects about 80% of the radiation emitted by a heat source at between 200 and 600 °C.

Alusi® ArcelorMittal 54+AS

Alusi® ArcelorMittal 54+AS

Stiffness - Ability to withstand high temperatures - Creep resistance

Alusi® sheet exhibits substantially higher stiffness at ambient temperatures than other systems.

Alusi® retains excellent mechanical properties at high temperature, giving it good creep resistance.

This enables it to be used in the following environments:

  • Engines, manifolds and catalytic converters,
  • Underbodies with very little suspension travel.
Creep resistance: Comparison Steel/Other indicative solution

Creep resistance: Comparison Steel/Other indicative solution

Mass savings: thinner gauges, down to 0.25 mm

Alusi® sheet has been developed in thin gauges, reducing heat shield weight.

ArcelorMittal can offer Alusi® sheet in 0.25 mm thickness, enabling heat shields to be designed with a 50% weight reduction relative to a conventional 0.5 mm thick system.

Stiffness and improved drawability: the embossed aluminised steel system

ArcelorMittal offers embossed Alusi® sheet in order to enable very thin gauges to be used while maintaining sufficient component stiffness.

Embossing facilitates secondary processing by simplifying the range of tooling and reducing the number of drawing operations required to produce the component.

Embossing also improves vibratory behaviour and increases stiffness of the component.

Embossed aluminised 0.25 mm thick steels are particularly competitive compared to alternative materials.

The combination of improved drawability and stiffness enables heat shields to be designed in 0.25 mm Alusi®, generating significant reductions in material costs compared to other materials. 

  • Embossed Alusi® heat shield in DX54D+AS 120  (thickness: 0.4 mm) 

  • Embossed Alusi®  heat shield in DX54D+AS 120  (thickness: 0.25 mm)

  • Alusi® heat shield in DX54D+AS 120  (thickness: 2 x 0.3 mm) 

  • Alusi® catalytic converter heat shield in DX55D+AS 120  (thickness: 0.5 mm) 

Fuel tanks and filters

The excellent resistance of Alusi® steel to attack by petrol, diesel and biodiesel fuels and its external corrosion resistance and deep-drawability make it the preferred choice for use in metal fuel tanks and fuel filters.

The DX56D+AS grade, for instance in 55 g/m² double-sided, is ideal for this type of application. Alusi® steels fully comply with fuel permeation standards as well as material recycling and biodiesel compatibility requirements. 

Fuel tank shell

Fuel tank shell

Corrosion resistance

The corrosion resistance of Alusi®coating has been demonstrated in a variety of fuel and atmospheric corrosion tests. Results show that the aluminised steel system enables 15-year service life to be attained for metal fuel tanks.


Most welding techniques can be used to fabricate shells (resistance seam welding, Soudronic®) and other components (MIG, MAG, braze-welding, etc.).

Deep drawing / Fuel filter

In order to cater for the demand in diesel filters made of Alusi® steel, ArcelorMittal has developed the ArcelorMittal DX56D+AS grade with low coating weight and a final surface treatment (EasyfilmTM), which preserves coating integrity and adhesion.

This combination is compatible with biodiesel.

Fuel filter

Fuel filter

Mechanical properties

Available grades

Show all
ArcelorMittal name Use YS (MPa) Rm (MPa) A(%) L0 = 80 mm r (90°) n (90°)
DX51D+AS Roll forming - Lock seaming 270 - 500 ≥ 22
DX52D+AS Average drawing 140 - 300 270 - 420 ≥ 26
DX53D+AS Difficult drawing 140 - 260 270 - 380 ≥ 30
DX54D+AS Difficult drawing 120 - 220 260 - 350 ≥ 34 1.4 0.18
DX55D+AS Difficult drawing for 600°< T < 800°C 140 - 240 270 - 370 ≥ 30
DX56D+AS Extra-deep drawing 120 - 180 260 - 350 ≥ 39 1.7 0.20
DX57D+AS Extra-deep drawing 120 - 170 260 - 350 ≥ 41 1.9 0.21

Mechanical properties for thickness > 0.7 mm.

(Mechanical properties for thickness < 0.7 mm: provided on consultation.)

Alusi® is also available in several higher-strength grades. Please contact us for further details

Surface appearance

Alusi® exhibits a polished surface (high reflectivity) with needle-shaped crystals visible to the naked eye. Alusi® retains its original appearance up to 400 °C with 80% reflectivity.


Consisting of 90% aluminium and 10% silicon, Alusi® is split into one ternary layer of alloy at the steel-coating interface, ranging from 4 to 7 microns, and an overlay of binary aluminium-silicon alloy.

Cross-section of Alusi®coating

Cross-section of Alusi®coating

Coating thickness

Unless otherwise specified, the standard Alusi® coating weights and corresponding thicknesses  offered are as follows (measured at 3 points): 

EN Standard 10346 g/m² double-sided µm per side
AS 60 60 10
AS 80 80 14
AS 100 100 17
AS 120 120 20
AS 150 150 25
AS 180 180 30
AS 200 200 33


VDA 239-100 Coating mass per side (Single Spot test) g/m² µm per side
AS30 30-65 10-20
AS45 45-85 15-28

However, other requirements may be considered. Please contact us.

Coating process

Alusi® is produced by continuous immersion in a bath of molten alloy made up of approximately 90% aluminium and 10% silicon.



Alusi® coating provides excellent corrosion protection, in hydrocarbon and outdoor environments and at high temperatures (650-800 °C).

The formation of stable and impermeable corrosion products (alumina) make this a long-lasting durable coating, clearly superior to other galvanised coatings when used for recommended applications.


The presence of a hard ternary alloy layer containing iron lends Alusi® coating a hardness that reduces the Lankford coefficient or R-value when measured in a tensile test.

By controlling this ternary layer and reducing the coating weight, however, Alusi® can be used for complex deep-drawn parts such as fuel filters and fuel tanks.

The use of prelube oils and of thin organic films (EasyfilmTM) improves the deep drawing properties even further.

Temperature resistance

Alusi® coating differs from other coatings in its ability to withstand high temperatures (650 °C and up to 800 °C for DX55D+AS) steel grade without delamination or scaling of the coating.


Alusi® coating retains its original shiny appearance up to 400 °C with 80% reflectivity.

This property makes Alusi® the ideal coating for use in thermal insulation applications such as engine heat shields and underbody parts.

Surface appearence

Alusi® is supplied with a matt finish; three types of surface finish are available according to customer requirements. A bright polished finish can also be created for certain applications. 

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