How long does powder coating last in the sun?

Powder coating is often used for outdoors objects and so it has to stand up to a lot of punishment over time. Even powder coatings in mild climates face prolonged UV exposure which can impact their finish and integrity sooner or later.

Some coatings will fare better than others in the presence of UV. So, how long does powder coating last in the sun?

Is powder coating affected by prolonged exposure to the sun?

Powder coating is inevitably affected by sun exposure. Some types of coatings are much more resistant to the effects of UV, but given enough time, a powder coating will show its age in the sun.

In powder coatings, this can often manifest as a phenomenon known as chalking. Chalking is a powdery, fine layer on the surface on the coating caused by exposure to radiation such as UV. This is common with epoxy powders which are notorious for faring poorly in the sun.

UV affects the chemical bonds in a coating, causing inclusions such as the resin and pigments to loosen and come to the surface as a chalk-like white powder, thus the name.

Powder coating has a finite life expectancy like any finish, and certain environmental factors may speed up degradation. These include coastal locations or weather conditions such as dust storms and acidic rain.

Incorrect cleaning can also cause a coating to fade faster than normal, particularly if harsh solvent-based cleaners are being used or high-pressure washers.

In environments where constant UV exposure or weathering are inevitable and unavoidable, an extra protective layer such as wax may be needed to protect the powder coating from premature breakdown. The right wax could also bolster the UV resistance of the coating.

If a powder coating has been weakened and begun to chip away from a metal object, UV may cause the metal to expand. As the metal cools overnight and continues a cycle of expanding and contracting, this could further crack and weaken the powder coating.

Does it fade?

Powder coatings are much more resistant to fading than liquid paint, but they will inevitably fade after so many years. This can occur due to the prolonged UV exposure, but there are other ways a powder coating might fade:

• High traffic or constant abrasion against the object—such as handrails, steps, or benches—could cause the coating to fade as its layers and finish are worn down.
• Staining from other chemicals being left to dry and affect the coating.
• Harsh or too-frequent cleaning, using pressure washers, solvents and chemicals, or abrasive items like scourers or steel wool.
• Substances that dissolve into rainwater, such as the fumes released by cars and machinery.
• Bird droppings left to sit on the coating, as bird excrement contains high amounts of uric acid.

It may be that a coating appears to be faded but simply needs a clean and a bit of maintenance. Whilst powder coatings do inevitably fade eventually, it could be that yours simply needs more regular care.

The original colour of a fresh powder coating should also be kept in mind when considering fading. A more deep and vibrant hue will be more noticeably faded over time compared to lighter tints, and chalking will be much more noticeable. Since all coatings will fade sooner or later, colours like vibrant red and blues should be chosen with care.

Knowing how long powder coating lasts in the sun is all well and good, but planning for when your powder coating will wear down in future is essential.

Is powder coating UV resistant?

Certain powder coatings are more suitable for use under constant UV exposure than others. The specific type of coating used will dictate how effectively it stands up to UV, and could mean a difference of several years in the overall lifespan of a coating.

It should be noted that powders with good thermal stability aren’t necessarily the best to use outdoors. For instance, epoxy powders are a kind of thermoset powder coating. Thermoset powder coatings crosslink and undergo an irreversible bonding process when cured, and this means they cannot be melted once finished and boast a high resistance to heat.

Despite this, epoxy coatings aren’t as suitable for UV exposure as other types of powder coating. As well as chalking, they can turn brittle and crack.

Polyester coatings cope well with UV exposure, being good catch-all coatings and highly suited to use outdoors. As well as good resistance to UV, they boast great flexibility and impact resistance, lessening the chances that UV exposure will find a weak point to exploit.

Acrylic coatings have good colour retention alongside their heat resistance, but can also be used as a clear coat to protect other coatings.

Hybrid powders can help override the weaknesses of certain powders, such as epoxy polyester blends that mean many of the benefits of epoxy powder can be retained whilst improving their flawed UV performance (though they may still be better suited for indoor uses).

How do I get the most out of my powder coating?

If you need to ensure the absolute maximum return on your powder coating, get in touch with Tomburn.

We apply powder coatings with the utmost care and expertise, ensuring there are no faults in the coating that will present problems farther down the line. We can give you our professional advice for maintaining and caring for the coating so that you get very best life out of it, guaranteeing it for years to come.

To find out more about durable powder coatings, contact Tomburn today.