Anodising

Why Anodise?

There are two main reasons for Anodising

The anodising process seals the aluminium, protecting it against elements such as light, oxygen and electricity! if raw aluminium is left in open air it will very quickly oxidise and turn white.
The anodising process provides an attractive finish in a range of colours, so are not just limited to just the usual aluminium colour, unless you want to of course

How anodising works!

Firstly the aluminium must be cleaned, using a caustic soda bath (caustic cleaning). The aluminium is then placed in a bath of sulphuric acid. Once the aluminium is immersed in the acid 15 volts is passed through the fitting, this makes the aluminium grow its own oxide. Once this happens the fitting is then removed and placed in the dye. The fitting then absorbs the colour into the structure if the fitting. The colour does not sit on top of the aluminium like paint would it actually changes the composition of the aluminium.

Available Colour

Standard: Black, Light (Satin Silver) & Dark Gray (Gun Metal Gray)
Custom Colours: Any colour can be requested (greater cost and build time my be required)

Depending on the time the aluminium is left in the dye tank determines the final colour. The longer the aluminium is in the dye the darker the final colour will be. The emersion time can vary from 30 seconds up to 3 minutes.
For a shiny finish the aluminium needs to be polished before the anodising process, but if an extremely reflective finish is what you require then the aluminium needs to be chemically brightened.

Chemical brightening

The chemical brightening takes place at the beginning of the anodising process. The aluminium is placed in a phosphoric nitrate bath at temperatures up to 105°C. This is done before colouring.

The film thickness for the highest brightness between 5-7 microns, the thinner the film the brighter the reflective surface will be.

Micron information

A micron is the unit of measurement that is referred to when taking about the film thickness of the anodising.

5 Microns - Decorative - Not to be handled
10-15 Microns - Decorative - light handling
25< - Architectural - Ok for handling and more importantly ok to be exposed to the elements.

There are two different types of anodising, hard and soft!
Hard anodising is done between +5° / -5°C, The benefits of hard anodising are that the film thickness is at 125 microns, this provides very good resistance against abrasion IE salt. Very good protection in black or dark gray.

Soft anodising is the standard type that is carried out on most of the aluminium products. Soft anodising is done at room temp (21°C) and has a film thickness of up to 25 Microns.