What is anodising and what are its benefits?

Anodising is an electrolytic process involving highly controlled oxidation that is used to produce oxide coatings on aluminium and some of its alloys.

The process of anodising involves several key steps, outlined below:

Step 1: Cleaning

Before the anodising process can begin, grease, dirt, and any other contaminants need to be removed from the surface.

Step 2: Pre-treatment

There are two popular pre-treatment options, depending on what the final product requires. These are bright dipping for a shiny appearance and etching for a satin-smooth, matte finish.

Step 3: Anodising/oxidation

The pre-treated piece is submerged in an electrolytic bath. The solution in the bath is then charged with a negative DC via electronic plates that are located inside the tub. Once the metal is charged, any positive ions are drawn-out and the negative phosphoric, chromic, or sulfuric ions are transferred to the metal in order to ‘fill-in’ the ionic gaps.

Step 4: Colouring

The final stage is the colouring. There are two main methods of colouring anodised metals: electrolyte colouring and integral colouring.

The key benefits of anodising

The first key benefit relates to the surface finish that can be provided. Anodised aluminium can give a finish which is totally uniform, rich, and simple to clean/maintain. It is also abrasion resistant.

The second benefit is that the oxide layer is strong and durable. This means it will not flake or peel as would painted surfaces. Additionally, it is not susceptible to rust.

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The third benefit is the control that the process gives over the appearance of the final piece/product. Colour can be added if desired and the rich, deep sheen is consistent and uniform.

Despite being a fairly niche market, in 2018, the value of anodised items sold in the UK amounted to £53m.

If you are looking for information on options when it comes to surface treatments, there are a number of specialists in the UK who can offer advice as to which surface treatments are best for which applications.

The fourth benefit is (because it is a poor conductor of electricity), the oxide coating is an excellent insulator. It is also wear/abrasion resistant and can cope with extremely high temperatures.

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One final key benefit is that the anodising process itself is environmentally friendly. The production processes used do not produce CO2 or harmful emissions, and anodised aluminium is 100% recyclable.

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