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The right finish for the right job: choosing between anodising and powder coating

Choosing the right protective coating or finish for your project is crucial. Whether you are in the defence, mining, engineering or architectural sector, you will need to review the specifications you have been given and determine what is required of the finish you choose. From colour and texture down to different levels of resistance to chemicals and weathering, you will need to align the finish to the spec.

Anodising and powder coating are both excellent and efficient finishes for your metal components, each with their own benefits and strengths. Read on to find out which finish fits which circumstances, to determine the best finish for your project.

Anodising and Powder Coating: What’s the Difference?

Anodising is an electrolytic surface treatment for aluminium components, which involves immersing them in an electrically-charged acid solution. This triggers the growth of a tough aluminium oxide layer to grow into and out of the metal part – its own in-built protective coating. 

Powder coating involves the application of a layer of powder particles through electrostatic attraction to a metal component.The powder is then cured in order to level and bond the molecules together, therefore creating a coating on the outside of the metal. 

Both coatings can be very effective and beneficial to your parts in different ways.

Type of metal

Anodising is a superior surface treatment for aluminium – as it converts the outside of the metal part into a hardwearing aluminium oxide skin. Aluminium oxide is a tough, hard and corrosion resistant material which will effectively protect the part. Other metals such as steel or copper cannot be anodised – this is also why it is important to use anodising grade alloys, such as the 5000 and 6000 series alloys, which contain magnesium and silicon. These alloys anodise especially well. 

Powder coating can be applied to both aluminium and steel, along with other substrates with special treatment. 

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Colour

If a specific colour is required for a specification, powder coating is typically the way to go. With near-limitless colour options, powder coating gives you the option to colour match very closely. Powder coating also produces consistent colour/gloss across batches, so it is an excellent choice if you know you will need to recreate a batch of components in the same colour months or even years down the track.

Find out more about the colours available from Dulux and Interpon, all of which can be offered as part of DECO’s powder coating services. 

Anodising can offer several different metallic colours, achieved by a dye process or electrocolouring. Dyeing involves filling the pores of the anodised aluminium with dye before it is sealed, while electrocolouring involves immersing it in an electrically charged bath with special ‘salts’ which help produce the colour. Electrocolouring can produce a wide spectrum of colours, including bronzes, while dyeing is best suited to blacks and colours which can be easily reproduced without too much variation. 

 

Texture

The type of texture required by your specification will also affect which finish you choose. Powder coating offers an extensive range of texture types, from matt and gloss to ripple and hammer effects. Different textures can also be achieved in anodising via a variety of pre-treatments, including etching and rumbling.  Longer etch times can achieve a matt finish, which may be crucial for components which must not reflect the light, such as camouflaged vehicles or machinery and equipment in full sun, where reflectivity may affect production.

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Tolerances

Some components require tight tolerances – they must fit together or move together as part of a working mechanism. In these situations, the coating must be durable enough to protect the part – but thin-film enough that it does not affect functionality. Anodised finishes can have a thickness as low as 15 microns while still providing excellent corrosion and abrasion resistance.

 

Corrosion Resistance

Both anodising and powder coating are effective in preventing corrosion – for different reasons. Quality powder coating undergoes specialised pre-treatment processes, decontaminating the surface of the metal and promoting effective coating adhesion to ensure the metal beneath is not exposed to elements which may lead to corrosion.

Once anodising is properly sealed, it is extremely effective at protecting against corrosion of the aluminium part beneath. 

 

Abrasion Resistance

Super Durable Class 2 powders are designed to be scratch resistant. When powder coated parts are properly pre-treated, this also ensures the coating adheres effectively to the metal and will not wear or peel off.

Anodising is another scratch resistant coating with its durable aluminium oxide layer. However,  for an exceptionally abrasion-resistant coating, hard anodising is another viable option. Created using special Zero Degree technology, hard anodising produces an extremely hardwearing aluminium oxide coating with a dense pore structure, which can withstand high impact and is effective for fast moving parts.

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Chemical Resistance

There are many different powder coating formulations available that can provide chemical resistance, even to alkaline cleaners. Anodising also exhibits high levels of chemical resistance, particularly to acids – but some alkali and mortars can damage the finish. It is important to determine which chemicals a part is being exposed to in its everyday use when choosing the right finish for it. 

DECO

Whatever your coating needs, DECO has a solution for you. With the only commercial hard anodising facility in NSW, MIL SPEC compliant anodising, Dulux and Interpon powder coating accreditations and a Qualicoat testing system, DECO provides durable, high-quality powder coat and anodised finishes for all your project requirements. 

To find out more, contact us. 

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