Anodising is an electrolytic passivation process used to increase the thickness of the natural oxide layer on the surface of metal parts.

Used on aluminium and its alloys, anodising forms a dense oxide layer on the surface of a part via electrolytic conversion.  This oxide layer resists abrasion and thus protects the underlying metal.  The thicker the oxide layer, the more protection it provides.  

The process is called anodizing because the part to be treated takes the role of the anode electrode of an electrical circuit.


Benefits of the AnoChrome Finishing anodising process:

  • Excellent corrosion resistance and metal protection
  • Improved hardness and wear resistance
  • Scratch resistant
  • Better adhesion for paint primers and glues than bare metal
  • Cost effective
Anodised Parts
Anodised Parts

Decorative and Colourful Protective Metal Coatings

The purpose of the anodising process is primarily to protect against metal corrosion, however an anodised metal finish has a pleasant aesthetic appearance.  The natural anodised colour is silver or light grey, depending on the aluminium alloy and its surface finish.  A great variety of other colours can be achieved using dyes.  The brightness of the finish achieved is largely dependent on the purity of the aluminium which can be enhanced by mechanical, chemical or electro-chemical means.

Hard and Natural Anodising

At Anochrome Finishing we are able to offer both natural and hard anodising. Generally hard coatings are required between 25 microns and 50 microns, although it is possible to achieve thicker deposits.  The hard anodised finish produced has a micro hardness of approximately 1100 Vickers.  This achieves excellent corrosion and temperature resistance, plus excellent electrical insulation.

The hard anodising process is available in various colours, but the resulting finish tends to be darker than natural anodising.

Architectural Application

An anodised aluminium finish is often used for external applications, where a combination of aesthetics, corrosion resistance and mechanical performance are required.

Points to Consider When Anodising

Suitable Aluminium Alloys

  • 1000 Series-Say 1080A, 1200A, 1050 are ideal for anodising
  • 2000 Series-Say 2014A, 2024 a satisfactory anodised layer may be produced
  • 3000 Series-Say 3103, 3105 are ideal for anodising
  • 4000 Series-Say 4043A,4047A a satisfactory anodised layer may be produced
  • 5000 Series-Say 5005, 5056, 5083, 5251, 5454 are ideal for anodising
  • 6000 Series-Say 6061, 6063, 6082, 6262, 6463 are ideal for anodising
  • 7000 Series-Say 7020, 7075 are ideal for anodising

Suitable Casting Alloys

Generally LM25 and LM5.  Some other alloys are suitable.  Contact us for recommendations.


Consideration should always be given to the jigging location as this will not be anodised.  An electrical contact must be made with each item to allow the anodising process to be successful.

Selective Anodising

If there are areas on the component which do not require an anodised finish, simply masking these areas will ensure they are excluded from the process.


Non-aluminium components will erode during the process and therefore must be removed prior to anodising.

Surface Finish

Any prior flaws on the surface of the part will become more apparent after anodising as the process maximises the appearance of the surface.  The surface finish prior to anodising should therefore be of a higher standard than that expected of the finished product.