Anodising is a finishing process used mainly on aluminium to improve durability, corrosion resistance and appearance. Rather than adding a separate coating, it changes the metal surface itself. This creates a protective oxide layer bonded to the material.

The Basic Process

The metal part is first cleaned to remove grease, dirt and marks. It is then placed into an acidic solution while connected to an electrical circuit. The component becomes the anode, which is where the name anodising comes from. When current passes through the bath, oxygen reacts with the aluminium surface and forms aluminium oxide. This layer grows evenly across the part and becomes harder than untreated aluminium.

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Colouring and Sealing

One advantage of anodising is that the new surface contains tiny pores. These pores can absorb dyes, allowing black, bronze, blue and other finishes. After colouring, the part is usually sealed.

Sealing closes the pores and improves corrosion resistance. It also helps the chosen colour remain stable for longer.

Where It Is Used

Anodising is common in architecture, transport, electronics and consumer goods. Window frames, bicycle parts, cookware and mobile devices often use anodised aluminium because it looks attractive while resisting wear.

Different methods can produce decorative layers or thicker engineering finishes for harsher conditions. Hard anodising is often selected for machinery parts needing extra toughness.

Because the oxide layer becomes part of the metal, it is less likely to peel or flake like paint. This makes anodising a practical treatment for many aluminium products.