Hard anodising
The technical hard anodising process is a combination of physics and chemistry. The hard and dense layers have an extremely high resistance - especially to abrasive stress. Hard anodised parts can be used wherever abrasive stresses occur. Due to the density and structure of the layer, hard anodised layers also have a high corrosion resistance. The dielectric strength per µm is 20 to 30 V per base material. Hard anodised coatings can also be impregnated with Teflon, which improves the sliding properties.
Hard anodising is essentially based on the same process as conventional anodising. In both processes, aluminium is converted into a protective oxide layer. However, the key differences lie in the specific parameters used when carrying out hard anodising. These include the acid concentration, the current density and the temperature of the electrolyte.
One of the most striking differences is the layer thicknesses that can be achieved. With hard anodising, layer thicknesses are achieved that are many times greater than with conventional anodising. These layer thicknesses can be up to 100 micrometres due to the alloy properties. Another important difference lies in the anodised pores, which are smaller in diameter during hard anodising. This leads to higher achievable hardnesses and improves the wear resistance of the treated components.
The hard anodising process is primarily used in areas of application in which components require exceptionally high hardness and outstanding wear protection. Examples of such applications include the aerospace industry, the automotive industry, mechanical engineering and many other demanding sectors. The hard anodising process therefore remains an essential process to ensure that components can meet the highest requirements in terms of hardness and wear resistance.
Grey, Black, Nature
Summary
- Not every colour can be used for hard anodising, and the appearance also differs from the anodising process. We will be happy to advise you.
- Our baths allow us to process workpieces with dimensions up to 105 x 295 cm. Uncoloured components, as well as black and RAL 8000 are possible in these dimensions.
- Much higher layer thicknesses are achieved, which can be up to 100 µm due to the alloy. In addition, the diameter of the anodised pores is smaller, which leads to higher hardnesses.
- High copper alloys with more than 2% copper content cannot be hard anodised.
The strength of hard anodising
Advantages
- High corrosion protection
- High abrasion resistance
- High hardness due to alloy of approx. 500HV
- High dielectric strength of 20-30 V per µm layer thickness
- Dimensional accuracy of your workpiece. It should be noted that only 50% of the generated layer thickness is noticeable as a "job". 50% of the layer diffuses into the base material. Please note this for fitting parts!
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Hard anodised
Properties
Due to the combination of the layer structure and the high layer thickness, a hardness of approx. 500 HV and a current-insulating layer with a dielectric strength of 20 to 30 V per um is achieved. Hard anodised coatings also have very good corrosion resistance. The layers can also be impregnated with Teflon to improve the sliding properties.
These properties enable a wide range of applications, e.g. in medicine and defence technology, aerospace, offshore, etc. All aluminium alloys with a copper content of less than 2% can be hard anodised. Half of the coating thickness is applied, with the other half diffusing into the base material.
Refinement with precision
Colour for hard anodising
One disadvantage of hard anodising is its limited colouring capacity. As these layers have a dark surface, they can only be coloured to a limited extent. However, the colouring of hard anodised components in the colour black is possible without any problems and offers an attractive option for certain applications. However, the possibilities for achieving other colours on hard anodised surfaces are more limited. Nevertheless, some limited colour variations can be achieved, although they may not be as varied as with other anodising processes.
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