Aluminium Alloys For Anodising

What Alloy Is Best For Anodising?

The best alloy is different depending on what anodising process is used and depending on what the end use of the component is, but by far the most common alloys that we see are 6061, 6082 and 6063. These are suitable for most applications with good corrosion resistance and anodisability. Many of our customers also like to use these alloys because of their machinability and strength. More information about which is best for each anodising process is below.

Decorative Anodising

Our preferred alloy for cosmetic work is 6063, although 6000 series are usually suitable. 1000 series are also good for decorative work, but are rarely seen because of their other shortcomings. If you want to be able to match parts together, it is essential that they are made from the same alloy. There can also be significant variations between different batches of the same alloy so it can be worthwhile to ensure that all components are made from the same batch of material if it is crucial that they match.

Hard Anodising

Hard anodising gives best results on 6061 or 6082 alloys, but 6000 and 7000 series aluminium is generally suitable for hard anodising. Hard anodising is possible on 5000 series alloys, but properties such as wear resistance will be compromised. 1000 series are suitable for hard anodising, but may exhibit some crazing which is an expected part of the process.

Metal Finishings Ltd offer hard anodising on 2000 series. Designers should be aware that there is additional risk associated with hard anodising 2000 series and many other companies cannot produce a true hard anodised finish on 2000 series, so supplier selection will be essential.

It is unwise to use alloys with a high non-aluminium content if the coating is to be heated or cooled because the non-aluminium components of the alloy act as crack nucleation sites in the anodising. For this reason, it is ill-advised to use hard anodised 2000 series and 7075 for parts that will be subject shrink fitting (freeze fitting) or baked.

Non-Decorative Sulphuric Anodising and Chromic Anodising

Generally, alloys in the 1000, 2000, 5000, 6000 and 7000 series are suitable for non-decorative anodising.

Corrosion resistance on 2000 series alloys is comparatively poor compared to 6000 series alloys. However, we have carefully developed an anodising process that ensures good corrosion resistance on 2000 series alloys and we perform simulated corrosion tests on anodised 2024 aluminium test pieces every month and are able to provide over 500 hours of salt spray resistance to ASTM B117.

Temper State

Components should be heat treated prior to anodising if this is required.

Castings

Castings are generally less suited to anodising, but it is generally possible to anodise them. Castings are often problematic for decorative work, wrought alloys are preferred for decorative work. In particular high silicon and highly porous castings should be avoided.

Your Purchase Order

Please tell us the type of aluminium used on your purchase order as this is a significant factor in how we anodise the part. Some alloys will require extra special care.

More Info and Specialist Advice

Please email us if you would like advice on which alloy to use. This page just gives general suggestions and our specialists will be able to provide more in-depth information.

Disclaimer

This page is provided for information only, it should not be considered advice and we cannot accept any responsibility or liability for your use of the information on this page. The information on this page is used and relied on at your own risk and you bear the sole responsibility for any outcomes. E&OE.

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