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Sapphire Aluminium Industries

Anodising Aluminium Sydney from Sapphire Aluminium

Anodising is a very old and established process and was developed for commercial applications in the early 1930's. It is still in service on buildings built in the 1950's, Anodising continues to stand the test of time today.

What is Anodising?
Is the process for producing a translucent film of aluminium oxide which forms an integral part of aluminium. This is produced by applying direct current through a suitable electrolyte (dilute sulphuric acid) in which the aluminium is the anode and a suitable material e.g. (lead) is the cathode.

How long does it take?
It physically only takes a few hours to process and pack a part. We need anywhere from a few days to a few weeks to plan and process projects. General Lead times of 1 - 2 weeks apply and lead times of longer than four weeks for anodising are rare.

What can be Anodised?
Sapphire's process for anodising only lends itself to aluminium extrusion, sheet and plate of certain alloys. As mentioned above anodising is a reaction with the alloy surface you wish to coat and the resulting coating will depend on the quality and purity of the alloy used. The following international alloys are recommended by Sapphire for consistent anodising results. All alloys should be Prime Billet, no remelt.
Extrusion
6060T5
6063T5
6463T5 (Used for high quality bright finishes)
Sheet
5205 H34

What is the biggest piece that can be anodised?
Sapphire can anodise extrusions and sheets within the following dimensions.
Length = up to 6.5 metres
Depth = up to 1.3 metres
Width = up to 300mm

How thick is the coating?
Anodising is a very thin coating of immense hardness measured in microns.
Internal uses are generally between 5um - 15um.
Exterior uses are between 15um - 25um (refer to guide on selection of Anodised Coatings)
A micron (um) is 1/1000 of a millimetre for example a cigarette paper is 7um.

How hard is Anodising?
Anodising is aluminium oxide which is the second hardest substance known to man, only a diamond surpasses anodising in hardness. Anodising can increase the hardness of the untreated aluminium surface by more than 3 times.

How long will anodising last?
Anodising properly specified and maintained will virtually last indefinitely. A normal service life in excess of fifty years for Sapphire AA25 coatings can be expected (subject to proper and regular maintenance), making the coating ideal for commercial and monumental use.

What are jig marks?
In order to anodise aluminium we need to hold on to the material in such a way as to pass an electrical current through it, this is commonly known as a jig mark. All items for anodising need to allow for a jig mark which is generally removed by the customer after anodising. You should allow the following for jig marks.
Extrusion = up to 50mm from each end
Sheet = Generally held in each corner up to 25mm. for large sheets in excess of 3.6 metres long additional marks maybe required on the top and bottom edges.

How do you colour the anodising?
Sapphire adds colour to anodising by one of three methods
1. Absorption
The anodised aluminium is immersed in a tank full of dye and the dye absorbs into the pores of anodised coating until the desired shade is obtained.
2. Two Step
The anodised aluminium is placed in a separate tank and a current is passed into the tank and tin in the form of stannous sulphate is plated into the pores of the anodised coating. These colours are UV resistant hence totally light fast.
3. Spectral®
Spectral is a three step process which manipulates the anodised coating to create different light refraction prior to 2 step colouring. This process creates a whole new palatte of colours that perform well against UV. (Refer to Spectral Tab for more information)

Colour Inspection
Anodising is like many wood veneers or marbles, it is a natural product that needs to be viewed in the terms of tonality of colour. When inspecting Anodised finishes for colour and finish tonality certain factors must be taken into consideration.
1. Light conditions
As the Anodised finish is translucent whether it is matt or bright finished it will tend to reflect light like gemstones, It this property that gives life to finish giving it a different appearance depending on the angle and intensity of the light source it is inspected in.
2. Distance from product viewed
to assist with colour inspection for anodised coatings, a distance of not less than 3 metres should be used for the inspection of Anodised coatings. This will help take away varying elements such as light reflecting and refracting from the different anodised surfaces.
3. Differences in perception of colour
Each person has a different perception of colour. This should always be taken into account when inspecting finishes.

Is anodising safe?
Anodising is a safe process that is not harmful to human health. An anodised finish is nontoxic and chemically stable. It will not decompose and increases the fire protection from 600 degrees Celsius to around 2000 degrees Celsius.



Sapphire Aluminium Industries Profile

02 4304 3555

19 - 29 Pile Road, Somersby, NSW, 2250

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02 4304 3555

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