Anodising is an electrolytic process that forms a new oxide layer on the surface of aluminium.

This anodic layer is hard, corrosion resistant, non-conductive and visually appealing.

Anodising is NOT an APPLIED COATING.

It is a process where the metal builds a new surface layer of microscopic cells that can be flooded with dye while open, then sealed to lock colour in - permanently.

It’s simply amazing and unique to aluminium.

Clean, racked parts are submerged in a series of baths that include:

1. A Degreasing solution.

2. An Etch being a solution of sodium hydroxide (caustic soda) to prep the surface for anodising.

3. Desmut bath which removes all non-aluminium impurities brought to the surface by the etch.

4. Anodising tank containing sulphuric acid with an electrical current to form the new anodic layer.

5. Dye tank with organic coloured dye.

6. Seal tank containing a nickel acetate solution, which closes off the open pores and locks in the coloured dye. If a natural burnished silver look is required then the dye step is skipped.

In between the key baths are rinsing requirements, so parts go through quite a few stages before they display that characteristic anodised lustre and finish.

At every step in the process, great care is taken to ensure your part achieves the anodic layer required for its purpose and visual appeal.

NOTE# An anodised surface is an excellent base for primer when applying secondary coatings.

Alloys in the 5000 series appear the most vibrant in a silver natural or coloured finish.

6000 series alloys will anodise and colour well, though slightly darker than the 5000 series.

7000 series can be anodised with a natural finish but is not considered a decorative alloy. Black is the only recommended colour.

2000 series alloy will anodise with a flat grey natural finish. Like 7000, black is the only recommended colour choice. and even then, there can be tiny pits present across the anodised surface. This is because there is a material in the alloy that the anodising proccess will draw out.

Absolutely! Check out the Before & After pic on our Top Tips page to see parts that have had their orginial anodic layer stripped off, then re-anodised and dyed black.

It’s a real money saver to refresh old parts, or simply change the colour scheme, rather than buy new.

Check out vids on our socials that show parts being stripped and re-anodised :-)

The anodic layer that is formed is measured in microns; a micron being a thousandth of a millimetre.

The higher the micron measurement, the greater the length of the pore structure and once sealed, the greater it’s resistance to wear and weathering.

For ease of understanding, think of the anodic layer graded in these 3 categories:

1. Indoor: 10-15microns

2. Outdoor: 20-25microns

3. Hard: 50-60microns

10-15microns is known as Type II anodising:

- Suitable for most general applications like bathroom fittings, car parts and machinery components.

20-25microns is known as Marine or a Semi-Hard anodise:

- Provides suitable protection to outdoor elements with 25mic recommended for components located in seaside situations.

- Widely used to protect aluminium surfaces in the building industry like window and door frames and balustrading for example.

- Recommended for parts that will be subject to substantive friction and wear.

50-60microns is termed either Hard Anodising or Type III:

- Provides lasting protection to parts being continuously subjected to friction like rubbing or piston action.

NOTE# Action can arrange your Hard / Type III anodising to be done to a very high standard at our sister plant.

It’s where the part is held by a tine to a rack. The contact that the tine has with the alloy is the point of delivery for the electrical charge that is critical to the formation of the new anodic layer.

Contact points will leave silver marks on the part where the anodic layer cannot form due to the compression of the racking tine against the metal.

Action will ensure that contact points are located in the most discreet position on your component.

We find it helpful if you indicate what is the visible surface or ‘face’ of a part, so that we can rack to ensure it is blemish free.

The best way to indicate visible areas or where you want the part racked is to provide clear written instructions or a sketch.

Do not use masking tape to write on or permament marker as we wil have to remove that pre-anodising.

If anodising MACHINED parts:

1. Ensure ALL flooding coolant is washed off thoroughly with water or solvent shortly after machining.

   Any coolant that dries on the part can be absorbed into the pores of the metal and will then act as a mask, preventing an anodic layer from forming. A natural finish will not reveal these markings, but a dyed surface certainly will showing the un-anodised areas as unsightly silver markings.

2. Cleaning blind holes with a squirt of brake cleaner and rinsing with water.

   Any residue left in the blind holes, especially threaded holes, splashes on the part’s surface when being flushed with water before the dye or seal step. This residue acts as a mask with little silver splash markings clearly seen against a dyed finish.

A flawless anodised finish is definately a team effort between machinist and anodiser :-)

If anodising SECONDHAND parts:

1. Remove other metal components (if you can) such as steel or stainless parts.

2. Degreaser, brush and a bit of elbow grease will clean oil and grime away for a clean surface that’s ready for the anodising process. If you don’t wish to prep your part beforehand - no problem as Action offers a cleaning service as well.

3. If your part is showing signs of corrosion, it may need to be sanded & polished out to ensure a good anodic layer will form. Action can check over the part and see if this prep is required. Again, this service can be arranged if needed :-)

Yes. 2000 & 7000 series alloys get processed differently to 5000 & 6000 series, so please tell us beforehand.

If we rack 2000/7000 series parts with 5000/6000 series parts, they will have a poorer surface finish and against a dyed finish the outcome is dissapointing.

To get the best finish with your anodised part, use a 5356 welding rod. These welds will anodise and absorb dye unlike other rods that will anodise a dark grey colour and will not absorb dye.

If the welding rod used is unknown, expect a grey weld finish as 6000 & 7000 series welding rods are more commonly used in manufacturing.

Fuel does NOT damage anodising. Action anodises components that are exposed to fuel or gas like nozzles, rails and fuel tanks.

An anodised surface is actually the best surface to protect alloy from fuel.

Yes, a section can be left as raw alloy when a masking technique is used to prevent that area from anodising. This is often required when electrical conductivity is needed because an anodised surface is non-conductive.

Unfortunately, NO.

Cast alloy is quite problematic to anodise unless you are getting a part especially cast and know that its composition will be suitable for anodising, with a maximum silicone content of 4%.

You can tell if your part is cast alloy with these clues:

• raised product/part number and/or logo

• raised mold joins

• flat grey colour

Only aluminium alloys can be anodised.

If you have parts that have other metal components attached, these must be removed beforehand otherwise they can be damaged in the anodising process.

Have a chat to us about this if you have parts with other metals attached.

An easy way to determine if your part is made of aluminium is the magnet test. Aluminium will NOT hold a magnet to it’s surface.

Even though other metals like brass and copper don’t hold a magnet, the colour differentiates them with aluminium being a silvery grey.

We ask that you do NOT use masking tape to wrap parts together to stop them rubbing during transit, or anywhere else on your item e.g. to write instructions on.

When removed, masking tape often leaves sticky gum residue that acts as a mask to the anodising process. The end result will be clearly visible non-anodised silver areas contrasting with the burnished natural or coloured dyed finish of an anodised surface. It is unsightly and so easily avoided.

Action will remove tape and clean the residue using white spirits to ensure a clean surface.

Simply wrap parts with materials like bubble wrap, paper or fabric.