Hard anodising service

This coating is much harder than the original metal and increases its resistance to wear and corrosion.

Thanks to its excellent durability, hard anodising is ideal for general engineering applications that require a heavy-duty, wear-resistant surface. Some common uses and applications include:

The aluminium component, which acts as the anode in the electrical circuit, is submerged in an electrolyte bath containing a chilled sulphuric acid mix. A cathode is also suspended in the bath and a current is passed through the solution between the two electrodes.

Oxygen ions are released from the solution and combine with the aluminium atoms at the surface of the workpiece, producing a thick, aluminium oxide coating.

Unlike some other finishing methods that simply coat the top of the substrate, anodising causes parts of the base metal to fully integrate with the coating.

As a result, the oxide coating cannot chip or peel like other surface coating technologies.

The process is typically used for functional, engineering purposes where there is less focus on aesthetics. However, standard sulphuric anodising tends to be used for commercial items where appearance is a consideration.

Unlike regular anodising, the process of hard anodising takes place in a refrigerated bath. The electrolyte solution is typically chilled to around 5°C, compared to standard anodising which is performed at a temperature of around 18 – 22°C.

Hard anodising also uses a lower concentration of sulphuric acid mix, as well as a higher voltage current. It’s these crucial differences that are responsible for producing the thicker, tougher coating for which hard anodising is renowned.

Here are just some of the reasons to choose Knees Engineering for your hard anodising and metal finishing requirements: