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Hard anodising

Highest wear resistance for aluminium surfaces

Hard anodising – The resistant surface finish for aluminium components

Hard anodising, also known as hard anodising or hard coating, is an electrolytic process for surface refinement of aluminium. Anodic oxidation creates an extremely hard, ceramic-like protective layer that protects the material against wear, corrosion and thermal stress. Particularly in demanding industrial applications, hard anodising is the first choice for durable and resilient aluminium components.

Hard anodising – developed for maximum loads

Hard-anodised aluminium surfaces offer decisive advantages for high-performance applications:

Extreme wear resistance

Ideal for components subject to high mechanical stress

Optimierter Korrosionsschutz

Langlebiger Schutz vor Umwelteinflüssen

High hardness & abrasion resistance

Hardness of up to 500 HV possible

Excellent thermal insulation

Ideal for thermally stressed components

Electrical insulation

Potential breakdown voltage of over 3000 V possible

Properties of hard anodised surfaces

Hard anodised coatings are characterised by a variety of functional properties:

Wear-resistant & scratch-resistant

Perfect protection for mechanical applications

Temperature-resistant up to 2,200 K

Ideal for high-temperature areas

Electrically insulating

High breakdown voltage for electrical applications

Very low thermal conductivity

Heat shielding due to oxide layer

Optimum adhesion

The layer is inseparably bonded to the base material

How does hard anodising work?

Hard anodising is an electrolytic process that is carried out in several precise steps:

Pre-treatment

The aluminium is degreased and cleaned to ensure optimum adhesion.

Anodisation

The extremely hard aluminium oxide layer is formed in the cold acid electrolyte through anodic oxidation.

Sealing

A final treatment provides additional corrosion protection and optimised coating properties.

Areas of application for hard anodised components

Hard-anodised aluminium components are ideal for applications with the highest mechanical, thermal or electrical loads:

Mechanical & plant engineering

Mechanically highly stressed components with maximum wear resistance

Aerospace

Lightweight but extremely robust components

Automotive industry

Optimal corrosion and abrasion resistance for chassis and engine parts

Electrical engineering

High-voltage insulation and thermal shielding

Maschinen- & Anlagenbau

Mechanisch hochbelastete Bauteile mit maximaler Verschleißfestigkeit

Luft- & Raumfahrt

Leichte, aber extrem widerstandsfähige Komponenten

Automobilindustrie

Optimale Korrosions- und Abriebfestigkeit für Fahrwerks- und Motorteile

Elektrotechnik

Hochspannungsisolierung und thermische Abschirmung

    Colouring & visual design options

    Hard anodised surfaces have a natural colour ranging from grey to black, depending on the aluminium alloy. Additional black colouring is possible through adsorptive colouring. Due to the dense and hard layer structure, other colours can only be achieved to a limited extent and require individual coordination.

    Technical specifications & dimensions

    Depending on requirements, different layer thicknesses can be realised.

    Usual layer thicknesses

    30 – 80 μm, in special cases up to 150 μm

    Layer growth:

    Approx. 50 % into the material, 50 % out of the material

    Due to the growth characteristics, material shortages can occur at sharp edges. Constructions with larger radii of curvature improve the layer quality and prevent chipping.

    What component sizes can be hard anodised?

    Procedure / ProcessingLength in mmWidth in mmDepth in mm

    Chromic acid and hard and sulphuric acid­anodise
    4600
    420
    1300

    Sulphuric acid and hard anodising, various colours
    2600
    300
    1000
    All product window sizes

    FAQ about hard anodising

    How does hard anodising differ from normal anodising?

    Hard anodising creates a thicker, harder and more wear-resistant oxide layer than conventional anodising. The layer is also more thermally and electrically insulating.

    Which aluminium alloys are suitable for hard anodising?

    In principle, almost all aluminium alloys can be hard anodised. However, the copper content should be below 2% to achieve optimum results.

    Is hard anodised aluminium conductive?

    No, hard-anodised coatings are electrically insulating. Depending on the alloy and layer thickness, the breakdown voltage is over 3000 V.

    Can hard anodised surfaces be coloured?

    Only black colours are possible due to the dense and hard structure. Other colours must be individually matched.

    How temperature-resistant are hard-anodised surfaces?

    Hard-anodised coatings are extremely heat-resistant and can withstand temperatures of up to 2,200 K for short periods of time.