Anodising is an electrochemical process that changes the surface of a metal to give it beneficial properties, this makes anodising very different to electroplating or powder coating as these coat the metal in another substance to give beneficial properties.  The process of anodizing is only suitable for some metals and is mainly used on auminium or its alloys.  Other metals that can also be anodised include Titanium, Magnesium and Zinc.  You may occasionally hear about 'anodising stainless steel' but this process, while giving stainless a range of colours,  it is technically not an anodising process.


In New Zealand most aluminium anodising is either, what is known as Type II sulphuric anodising or Type III sulphuric anodising.  Of the two types of anodising commonly used in New Zealand, Type II is most used.


Type II sulphuric acid snodising - This provides both a decorative and protective finish with medium wear resistance.  The coating thickness can be from as little as a couple of mircons thick on car trim to 25 microns on marine or coastal applications.  The anodised coating that is produced is porous and this allows for the application of colour through dyeing.


Type III sulphuric acid anodising - This gives a much harder and thicker coating than Type II anodising an while not strictly a decorative coating it gives excellent wear resistance.  This coating is commonly referrer to a 'hard anodising'.  The colour range for hard anodising is more limited, as the colour is a result of the anodising process.