Anodising is an electrolytic process that thickens and toughens the naturally occurring protective oxide on aluminium products. Enhancing the natural metallic lustre, the process creates an extremely durable finish that has stood the test of time. Unlike powder coating or painting the anodic coating is a part of the metal and as the oxide layer is porous, it is able to absorb colour. The result is a corrosion resistant and decorative finish available in many colours.
Specialising in the components and smaller products (up to 2.4 metres) end of the market, Anodizers has established itself as a leader in quality anodising with a reputation for competitive pricing and delivery. A member of the Australian Anodisers Association of Australian, Anodizers’ process is compliant with Australian Standard 1231.
The range of products we cater to is endless from building materials to marine equipment, engine parts, bikes, climbing equipment, lights of all kinds to hinges, designer pieces and most notable the finish on the Sydney Olympic and Paralympic Torches and the Athens Olympic Torches.
For examples please visit our photo gallery.
How Is It Done?
The anodising process has five stages:
1. Cleaning the Surface
2. Finish. Anodizers offers three finishes:
a. Matt / Etch / Satin - liquid caustic is used to strip away the very outer layer removing and blending surface scratches or blemishes
b. Semi-bright / OBD / Semi-gloss – a mixture of phosphoric and sulphuric acids chemically enhance the surface finish
c. Bright / Gloss - a chemical brightening process using a mixture of phosphoric, sulphuric and nitric acids in proprietary product also known as Phosbrite or Metalbrite.
3. Anodising in a temperature controlled 10% to 15% sulphuric acid solution product is immersed on racks and effectively becomes the anode with the tank as the cathode for this electrolytic process. Time in the anodising tank will vary the thickness of the anodic coating ranging from 6um to 25um. ("um" denotes microns with 1um the equivalent of 0.001mm)
4. Clear or Colour. The anodic coating created from the anodising process is porous and as such can take colour. Anodizers' offers a wide range of colours (see Colour Chart).
5. Sealing. A critical stage that that seals the anodic coating for colour and weather fastness. The product is submerged in 80 degrees to 85 degrees water with a nickel acetate additive that enhances the sealing process.
What Are The Benefits of Anodising?
- Corrosion Resistance / Weather Proofing
- Durability / Abrasive Hardness - anodising is a reacted finish that is integrated with the underlying aluminium for total bonding and unmatched adhesion. As such the finish will not peel or chip.
- Appearance - enhances the natural metallic lustre retaining the appearance of aluminium. It is a contemporary look that compliments other materials such as timber, stone, glass and other metals such as stainless.
- Machined surface friendly - anodising is not going to affect the function of machined surfaces. The process should have an immaterial affect on dimensions however tolerance critical work should be advised to Anodizers’ staff prior to commencing the process.
- Health and Safety - an anodised finish is chemically stable, will not decompose, is non-toxic and is heat resistant to the melting point of aluminium. Anodizers process is compliant with food grade standards.
Anodised coatings will be affected by contact with materials that are acidic or alkaline. As such compounds such as wet cement, acid or alkaline cleaners such as in dishwashers should be avoided.
Cleaning should be done using warm water and a mild soap solution. Greasy deposits may require a soft cloth with white spirits or thinners.
Alloy Characteristics and Anodising?
Different alloys exhibit different qualities of strength, machinability, extrusion, sheet, corrosion resistance etc. This is also the case for their ability to be anodised. Set out below is a general guide of alloy grades and the quality of anodising that can be expected:
Excellent / Good:
6060, 6063, 6106, 6262, 5005, 1200
Medium to Good:
6005, 6061, 6351, 5083, 5251, 5052
- The condition of the raw component is very important in the anodised finish. Whilst etching can flatten or blend surface scratches any deeper scratches or chips will not be removed. Chemical brightening will often enhance any scratches or imperfections in the raw product.
- Welding or filler rod should be anodising compliant. Note that welding will change the characteristics of the alloy and whilst still anodised there maybe colour variation.
- Assembled parts can cause anodising problems in two ways:
- Non aluminium fastenings or rivets need to be removed as they will be attacked during the anodising process or hinder the anodising on the part.
- Leaking from joined parts will impact on the anodic coating, in particular coloured parts.
- Different alloys will anodise in different ways. As such it is preferable, though not essential, to have all parts from the same alloy.
- Blind holes and other machined cavities can trap chemicals that are difficult to remove during rinse stages.
- Painted product cannot be anodised.
- Anodised product can be stripped and re-anodised.
- Any glue or residue such as from a PVC coating can impact on the anodising. This can usually be removed with the use of thinners.
- Slightly corroded product may have the corrosion points magnified by the anodising process.
Aluminium Conversion Coatings
Conversion Coatings provide corrosion protection and paint adhesion for painted and unpainted aluminium surfaces. Unlike Anodising, the conversion process retains the electrical conductivity of the aluminium and as such is frequently used for electrical components and equipment.
Chromate conversion (also known as "Alochrome", "Alodine", "Aluminium Passivation", "Iridite" "Yellow Chromate" "Clear Chromate") is a chemical treatment
process that converts the surface of aluminium products. Anodizers has capacity for product up to 1.9 metres. The converted surface provides corrosion
protection as well as enhancing the ability for subsequent processes such as painting, to bond to the surface.
Anodizers offers the traditional yellow chromate Alodine 1200s as well as the new Alodine 5992 that is compliant with RoHS (European Directive 2002/95/EC) as regards electrical products and components. Please ask our staff about the latest developments and available services in this regard.
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