anodising

Anodising is an electrochemical process used to increase the thickness of the natural oxide layer on the surface of metals, primarily aluminium. It is an electrolytic passivation process that forms a protective oxide coating on the surface of aluminium. This oxide layer is significantly thicker than the naturally occurring one and offers improved corrosion resistance, wear resistance, and the ability to accept dyes for colouration.

The anodising process involves immersing the metal part, acting as the anode, in an electrolytic solution, typically containing sulfuric acid. An electric current is passed through the solution, causing oxygen to be released at the anode's surface. This oxygen then reacts with the metal to form a porous oxide layer. The thickness of this layer is controlled by the duration of the anodising process and the current density.

After the oxide layer has formed, it can be sealed, usually in hot water or a chemical sealing solution, to close the pores and enhance its protective properties. This sealing step is crucial for optimal corrosion resistance. Anodised aluminium can be produced in a variety of colours by introducing dyes into the porous oxide layer before sealing, or through electrolytic colouring techniques. The process is widely used in industries such as aerospace, automotive, architecture, and consumer electronics due to its durability and aesthetic versatility.