If you apply powder coating to aluminium surfaces, this will help to protect them from corrosion.
But although powder-coating provides long-term durability, it is not completely invincible to the impact of the elements.
Therefore, the short answer is that powder-coated aluminium doesn't rust, but it can corrode if the powder coating fails
Rust is a form of corrosion. It’s an iron oxide that forms from a reaction between iron and oxygen when water and air moisture are present. Over time, an iron mass can convert to rust completely, causing it to disintegrate.
The surface of rust is flaky and offers no protection to the surface underneath.
However, as a form of corrosion, rust only applies to iron and its alloys, such as steel.
Corrosion is a natural process that comes from a chemical reaction between materials and their environment. The most common form of corrosion involves the oxidisation of metal surfaces in reaction to various agents. The atoms in metal bond with oxygen, gradually breaking down.
Aluminium is prone to corrosion because it oxidises faster than steel. When this occurs, a hard, white-coloured skin forms on its surface. This process will only stop once all the atoms in the aluminium have bonded with oxygen.
Unlike rust with steel or iron, this form of corrosion is non-destructive to aluminium, but the oxidation process leaves the metal surface looking unattractive.
Applying polyester powder coatings protects aluminium surfaces from corrosion. However, there are conditions and circumstances where powder coatings can fail.
When this happens, despite its powder coating, aluminium can start to corrode.
Polyester powder coating is should protect aluminium, providing a long-lasting, tough coating. But in certain circumstances, it may not last as long as it should.
Why should this be the case? The reasons are normally due to problems during the powder coating process.
If something goes wrong during the process, the aluminium surface can end up with various issues:
Filiform corrosion – worm-like filaments appear under the powder coating finish, lifting it away from the metal, due to less effective pretreatment methods before applying the powder coating
Orange peel effect – the finished surface is not smooth due to a faulty application of the powder coat
Failure of the powder coating to stick to the surface – because of either the insufficient pre-treatment or faulty application of the powder coating layer.
Properly and carefully applying powder coating to aluminium surfaces should prevent corrosion.
But it’s also important to clean and maintain these surfaces once they have been coated. This is especially true in situations where they will face exposure to outdoor weather conditions. One example is powder-coated aluminium window frames.
There are remedial measures you should take if powder-coated aluminium surfaces become damaged and are therefore susceptible to corrosion.
One solution is to touch up any damaged areas with colour-matched liquid paint. This can work where there has been fading due to oxidation, or where there are scratches or blemishes.
Wear and tear can reduce the overall effectiveness of powder coating, so it’s important to keep on top of it.
Where there are more serious signs of corrosion, the best solution is to get the part or product re-coated.
But with a professional application of powder coating to aluminium surfaces in the first place, these types of issues are far less likely to come up.
For more information about aluminium powder coating, please contact us.