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Understand Anodising and the Different Types


Note: this is a partnered post and consideration was received for its publication. CC-licensed image of the anodised aluminum exterior of the National Museum of Australia by Sam Ilic.

The surfaces of buildings need to be protected against damage from the elements, including fierce sunlight and heavy downpours. Anodising is one effective way to make sure that buildings don’t become worn or damaged.

The process of anodization is a relatively straightforward one: Anodising is an electrolytic process for creating a protective oxide layer on the surface of aluminium. The surface of the building is treated with an acid solution which creates a protective oxide layer.

Natural anodised aluminium has several benefits. Firstly, it lasts a very long time and the process won’t need to be repeated for at least a couple of decades because the surface won’t get chipped. Paintwork will also stay intact. Secondly, anodising makes surfaces easy to maintain because dirt will be repelled by the protection. Thirdly, anodised surfaces are low-maintenance which means that people can get on with running their business. Next, the anodising process can give the exterior of a building a ‘facelift’ and make it look brand new. Finally, the chemicals used during the process are completely safe so there will be no adverse health effects for people who are using the building. Natural anodised aluminium by Anodisers in WA passes rigorous safety standards.

There are several different types of anodization.

Chromic Acid Anodising (Type 1)

The first anodising method invented uses chromic acid in order to achieve the desired results. The chromic acid produces a thin film of 0.5 μm to 18 μm. This type of film is more opaque than other types and is good at self-healing. Usually, this type of anodization is used prior to painting the surface.

Sulfuric Acid Anodising (Type 2 and 3)

Sulphuric acid is the most widely-used acid for anodization. This comes in two types of application. The first type (2) produces a layer of protection between 1.8μm to 25μm thick. Coatings thicker than this are known as Type 3. These types of coatings need to monitor more closely than Type 1 in the production stage. The thicker the application, there more protection there is against damage and wear.

Organic Acid

An organic acid is used to produce different shades when the anodising process has been completed. The organic acid produces yellow colours of different varieties. This is important if people want to give a specific tint to the outside of a building. Organic anodising can achieve a thickness of up to 50 μm.


Phosphoric acid can be used as a treatment substance and is most commonly used before adhesives like cement are added to the surface.


Plasma electrolytic oxidation is used where higher voltages occur. This process creates a more ceramic-like coating than the other processes which have been described previously in the article.

Anodization may seem like a complicated process, but hopefully, this article has made it seem much simpler. It is important to research all the different types of anodising before a final decision is made. People need to decide which method will produce the best results for their building by consulting with a professional company. Why not start the process today?