In anodising, cleaned aluminium is made the anode in an electrolyte, most commonly sulphuric acid. Current grows a controlled, porous aluminium oxide layer from the metal itself. The pores can be coloured with dyes or electrolytic colouring and are then sealed. Coating thickness is measured in microns, and architectural specifications set minimum thicknesses by exposure class. Hard anodising uses colder baths and higher current to produce thick, wear-resistant layers.
Why it matters when buying
- Alloy and billet quality strongly affect results: 6063 and 1xxx grades anodise brightly, while high-silicon or high-copper alloys give dull or patchy finishes.
- Poor homogenisation or die lines show up as streaks after anodising.
- Specify coating thickness, colour and shade range, and sealing quality, and ask how they are tested.
- Anodised parts need careful packing, since scratches cannot be touched up easily.
Typical uses
Architectural extrusions, facade panels, consumer electronics, cookware, reflectors and machine parts. Anodised scrap is generally treated as cleaner than painted scrap. Compare with powder coating.