Powder-coating and anodising are the most common types of finishes for architectural facades, but choosing the suitable finish will depend on many different variables.
In a nutshell:
- Coatings for architectural façades come in a mind-boggling range of colours and finishes
- The two main types of finishes are anodising and powder-coating
- When sizing up the pros and cons of each type, think about metal protection as well as the desired colour
- Anodising is harder-wearing but more expensive
- Powder-coating is available in standard RAL colours, premium ranges to mimic anodising, and even specialist finishes that look like wood
- The grade of aluminium can dictate the type of coating to choose
The use of aluminium panels as important design features on architectural façades means there is now huge demand for a range of colours and finishes.
First though, we need to ask ourselves an important question:
Colour or protection?
The answer is both. Whether powder-coating or anodising (and we’ll come to the difference in a moment), both processes not only help architects create distinctive landmarks in our towns and cities, they also extend the life of the metal in all types of challenging locations.
- Powder-coating is applied as a dry powder that is applied electrostatically and cured under heat or ultraviolet light. It is used to create a hard, protective layer that is tougher than conventional paint.
- Anodising is an electrolytic process to increase the thickness of the oxide layer that appears naturally on the surface of exposed aluminium and increases resistance to wear and corrosion.
Types of powder-coating
- Standard powder-coating is available in a range of RAL colours. But don’t be deceived by the term ‘standard’ - it still provides protection against the elements, and offers Class 2 resistance to fading from UV light. Some colours are more expensive than others, though.
- Premium powder-coating is available with a range of metallic finishes that mimic anodising but are much less expensive.
- Special powder-coating can provide a textured finish in a multi-stage process, and can be made to look like CORTEN steel – or even wood.
With all these options, you might be asking why anyone would choose anodising. Three main reasons. It’s longer-lasting, non-combustible and better-suited to the corrosive salty environment of maritime locations.
Read more about the fire ratings of powder-coated and anodised finishes.
Read more about protecting aluminium in maritime locations
What about colour consistency?
When coating small objects, colour consistency is seldom a problem. But multi-storey car parks, office blocks and public buildings are not exactly small. Coating in batches is necessary. And while anodising offers consistency across batches (often years apart if replacement panels are required), powder-coating requires careful attention to detail. Here, you should expect a powder-coating specialist to match every new batch to the previous one. Short-cuts could lead to inconsistencies across a façade.
Does the type of aluminium matter?
Not surprisingly, yes. Use higher grade aluminium and the options for coatings are better. The most commonly used high-grade aluminium used in the façades sector (6063) is suitable for anodising and powder-coating.
Spend less on 1050 Grade aluminium and it gets complicated. Powder-coating can create slight colour variations (even with the most careful matching) so it’s best to go for more expensive anodising instead.
55HX and J57S are high-quality, branded grades of aluminium that are ideal for façades. After anodising, they are both weather, corrosion and UV resistant. What’s more, anodise a new panel of the same type years later and you’ll get an exact colour match.
Are there standards for coatings?
Qualicoat is a not-for-profit organisation that verifies the quality of coating materials and processes for its members. So, it’s best to look for an approved applicator. Qualicoat also rate coatings (from standard Class 1 and ‘super-durable Class 2 to the top-end Class 3) in terms of their durability and resistance to UV fading. They’ve recently introduced a special ‘seaside class’.
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