Powder coating is known for being tough, durable and long-lasting – so when you see a powder-coated surface starting to peel, flake or lift, it can be more than a little frustrating.
After all, wasn’t powder coating supposed to be virtually indestructible? Well…not quite.
Powder coating is an extremely durable finish, but the quality and longevity of the coating depend on what happens before, during and after the powder is applied. Get any of those stages wrong and even the best powder coating can eventually fail.
So, what causes powder coating to peel? Here are five of the most common mistakes – and what can be done to avoid them.
If there’s one thing to remember about powder coating, it’s that good prep equals good coating.
Before powder can be applied the surface needs to be properly prepared. Any dirt, grease, oil, rust, old paint or other contamination left on the substrate can prevent the powder from properly bonding to the surface.
It might look perfectly fine when the coating first comes out of the oven, but if there’s contamination underneath it, the adhesion simply isn’t going to be what it should be. And that’s when problems can start.
Depending on the material and the condition of the component, preparation might involve cleaning, degreasing, blasting, stripping existing coatings or chemical pre-treatment.
Skipping or rushing this stage in an attempt to save time can be a false economy. A coating that fails prematurely means more time and money spent removing it, preparing the surface again and recoating it.
The lesson? Don’t underestimate the preparation.
Powder coating isn’t a magic eraser.
If you’re dealing with a component that’s already rusty, heavily corroded or covered in an old, incompatible coating, simply putting a new layer of powder over the top isn’t necessarily going to solve the problem. In fact, you could simply be hiding the problem temporarily.
Rust and corrosion can continue to develop underneath the coating, eventually causing bubbling, lifting and peeling. Similarly, an existing coating that isn’t properly bonded to the substrate can become the weakest link in the whole system.
This is why assessing the condition of the item before deciding on the coating process is so important.
Sometimes the best approach is to remove everything back to the original substrate and start again.
That’s where processes such as paint stripping or abrasive blasting can make a real difference. Starting with a clean, properly prepared surface gives the new powder coating the best possible chance of achieving strong adhesion.
For many applications, cleaning the surface isn’t enough.
Metal substrates may require a pre-treatment process to improve adhesion and provide additional protection against corrosion.
There are different pre-treatment systems available and the right choice depends on factors such as the substrate, the environment the finished product will be exposed to and the performance requirements of the project.
Get this stage wrong – or miss it altogether where it’s required – and you can compromise the performance of the entire coating system.
This is particularly important for components that are going to face challenging environments such as moisture, chemicals, coastal conditions or outdoor exposure.
A powder coating might look fantastic when it leaves the coating line, but its real test comes later. A great-looking finish isn’t necessarily a great-performing finish.
Powder coating isn’t simply a case of spraying powder onto metal and then giving it a quick blast of heat. The powder needs to reach the correct curing conditions for the required amount of time.
If the part doesn’t reach the correct temperature, the powder may not cure properly. If the coating is exposed to excessive heat or the process isn’t controlled correctly, the coating’s properties can also be affected.
And there’s another important point. Oven temperature isn’t necessarily the same as the temperature of the component itself.
A large, heavy steel component will take longer to reach the required temperature than a small, lightweight part. That’s why experienced coaters pay attention to the actual curing requirements rather than simply relying on the oven’s temperature display.
An incorrectly cured coating can suffer from poor adhesion, reduced durability and other performance problems. In other words, putting the oven on the right temperature is only part of the story.
Not all powder coatings are created equal and choosing a powder isn’t simply about picking a colour from a chart.
Different powder formulations are designed for different applications and environments. For example, a coating intended for an indoor application may not be the right choice for a component that will spend its life outside in the British weather. A finish exposed to coastal conditions may have very different requirements from one used inside a factory.
Then there’s the question of appearance. Gloss, matt, satin, textured and metallic finishes can all be available, but the visual appearance is only one part of the specification. The powder needs to be appropriate for the substrate, environment, expected performance and end use.
Choosing the cheapest or most readily available powder isn’t necessarily the most cost-effective option if the coating needs replacing sooner than expected.
The good news is that most coating failures aren’t inevitable.
A properly specified powder coating system, combined with thorough preparation and careful application, can provide a highly durable finish that lasts for many years.
The key things to consider are:
And perhaps most importantly, don’t cut corners at the preparation stage.
If your powder coating is peeling, bubbling, flaking or simply not performing as expected, don’t assume the answer is another coat.
Talk to Tomburn about the problem. We can help identify what may have gone wrong and advise on the best approach to getting your components back to a durable, high-quality finish.
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