Three types of anodising

Anodising is a useful way to strengthen a surface and enhance its properties, as well as improving its appearance. There are different types of anodising, with various advantages and disadvantages, so you need to understand how to choose the most appropriate form.

What is anodising?

At its most basic, anodising is when you cause a surface to oxidise, generally by submerging it in an acidic solution, then encouraging oxygen to be absorbed by the surface through use of voltage. This creates a hard coating. Examples include aluminium oxide and titanium oxide, as seen at www.poeton.co.uk/surface-treatments/anodising. It may be combined with other processes, such as painting.

Sulphuric acid anodising

This is the most common type of anodising, using a solution of sulphuric acid. You can create a range of different colourings and thicknesses through use of different voltages, though films of titanium oxide will generally be thinner than aluminium oxide films.

Hard anodising

Hard anodising is generally less concerned with colour and appearance. As the thickest type of anodised coating, it is used in situations where durability and electrical resistance are vital. It still uses sulphuric acid, but the temperature is lower whilst the voltage and concentration of acid are both higher.

Chromic acid anodising

Rarer than the other types of anodising, this method creates a thinner coating than cannot necessarily supply consistent colouring, but is particularly well-suited to maintaining fatigue strengths. It is most commonly used in castings.

Now you understand the different types of anodising, you can choose which of the three methods is most suitable for your specific needs.