Aluminium is widely regarded as one of the world’s most important materials – with uses in almost all sectors of the world. As with most metals, the finishing you choose for your aluminium is important; and often depends on what the metal is being used for.
When you apply a finish to aluminium, it often serves a purpose to either promote a new surface or to preserve an existing one. The finishing may make the aluminium more visually and functionally desirable.
Aluminium finishing’s can be broadly split into four different categories:
• Mechanical finishes
• Chemical finishes
• Applied coatings (such as powder coating)
With aluminium being a metal, the finishing process is often similar to other metals. However, with aluminium having certain unique characteristics, such in the case of aluminium alloys, special equipment is often used as a way to allow for a higher quality finish.
Mechanical finishes rely on a process which removes metal by abrasion (such as polishing, buffing, blasting or grinding). It is also possible to apply a texture by way of force (such as shot peening and embossing). Because aluminium is a much softer metal compared to Steel, for example, it is of paramount importance that lubrication is used to ensure that damage doesn’t result.
Aluminium can be treated with a chemical finish, and these are usually categorised into five different classifications – cleaning, brightening, Conversion coatings, Etching and Immersion plating. Each of these has their own uses, advantages and disadvantages.
Cleaning treatments are primarily done to remove oxides inhibitive to final finishes, as well as soils.
Etching is done to achieve different levels of surface mattness.
Brightening treatment is used to create a high surface lustre.
Conversion Coatings are mostly done for visual purposes to achieve the desired surface film.
Immersion Plating is the process of depositing metallic surface coatings.
Anodising is a method whereby the natural layer of oxide on the aluminium is artificially increased. It is an electrochemical process which means that a current is passed through the aluminium. If required a dye can be added to provide a range of anodising colours, gold, nickel and black. The most common colour being silver (self-colour), gold, black and bronze.
Powder coating is the method whereby we mix and combine substances such as pigments, levelling agents and curatives to achieve the desired coating. These ingredients go through a process of melt mixing, followed by a cooling process and finally a grounding process.
The coating is applied to the aluminium via a spray gun, which allows for a pristine finish. After the coating, the aluminium enters a curing oven to finish off the coating.
This treatment option is one of the most popular aluminium treatment options. You can choose from a very large range of colours, and gloss levels matt to a high gloss as well as offering a derivable protection which makes it great for uses where the aluminium has to be aesthetically pleasing.
Each of the above four treatment options has their own distinct advantages and disadvantages. Each serves a unique purpose; whether to protect the aluminium or to apply a visually aesthetic coat.