The Anodising Process Explained

Although aluminium is naturally resistant to corrosion, certain environments and applications can still cause it to tarnish, oxidise or degrade over time. Anodising is the process used to significantly enhance that natural resistance, while also delivering a consistent, attractive finish that protects the metal’s long-term appearance.

The process works by using the aluminium itself as an anode within an electrolyte bath. When a cathode is placed inside the tank and an electrical current is passed through the solution, oxygen reacts with the aluminium surface to form a dense anodic layer. The longer the aluminium remains in these conditions, the thicker and more protective that layer becomes.
Because this layer is created through chemical reaction rather than applied as a coating, it cannot chip or peel. The result is aluminium with significantly improved resistance to wear and corrosion, enhanced aesthetic qualities, and — importantly — a material that remains 100% pure and fully recyclable.

Anodising is also the stage at which colour can be introduced, allowing aluminium to be finished in a wide range of consistent, durable tones.

How the Anodising Process Works

At its core, anodising is a controlled and refined version of aluminium’s natural oxidisation process. While straightforward in principle, achieving a high-quality result demands considerable expertise, precise equipment, and carefully managed conditions.

The process follows these key stages:

The aluminium component is submerged in an electrolytic solution bath, with the cathode fixed to the inside of the tank. An electrical current is then passed through the bath, causing oxygen to form on the surface of the anode. This drives the growth of a metal oxide film directly on the aluminium surface. The thickness and quality of this layer is influenced by factors including the concentration of the solution and the temperature at which the process is carried out.

Once anodising is complete, the surface of the metal is highly porous. This is the point at which dye can be introduced — the open pores readily absorb colour, allowing the finish to be altered to suit aesthetic or specification requirements.

The final stage is sealing. To prevent the porous surface from attracting dirt and contaminants, the pores must be closed. This is typically achieved by immersing the aluminium in a bath of de-ionised water at elevated temperature, effectively locking in the finish and completing the protective layer.

 

 

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