When it comes to powder coating, more coats does not necessarily mean better performance. Here are a few things to consider when deciding how many coats to spray.
When to Spray a Single Coat of Powder Coating
At Kaser, we spray a single coat of powder 90% of the time. Why? Because that’s all most parts need. Our stock powders are hand-selected to perform well outdoors without primers or clear coats, saving our customers money. We’re also diligent about checking film thickness, ensuring that the single coat is thick enough to protect the part long term.
When to Spray Two Coats of Powder Coating
Blasted parts require thicker film. This could require us to spray a second coat of powder. Blasting leaves behind a surface profile – tiny valleys that must be filled with powder, and peaks that must be adequately covered. In these instances, we may spray a second coat of the same powder, taking the overall coating thickness from roughly 3 mils to 5mils.
As a side note, whether you’re spraying one coat or two, I recommend aiming for 3 mils of powder per coat. An operator could conceivably build 5 mils in one coat, but that’s a recipe for orange peel. Aesthetically, you’ll be happier with two thinner coats of the same powder than you would from a single, thick coat.
When to Spray a Primer and a Top Coat
Occasionally, I will spray two coats of different powder on a part. Parts destined to encounter chemicals, for instance, could benefit from an epoxy primer under a polyester top coat. These scenarios are rare. Most of the time, one or two layers of the top coat provides adequate protection without requiring us to change colors and clean the booth between coats. I always have to balance the customer’s needs against the shop’s overall efficiency.
When to Spray a Clear Coat
Customers ask me all the time whether their part needs a clear coat, and the answer is usually no. Clear coats are useful for metallic coatings, or powder formulations that aren’t UV-resistant to begin with. Kaser only stocks powders that are already UV-resistant. Additionally, clear coats are often finicky to apply – any bubbles or imperfections will require that the part be taken back down to bare metal and fully reworked.
If you can achieve corrosion protection and UV-resistance in a single coat, do so. It will save the customer money. If you need more film thickness than a single coat can provide, however, I suggest to spray two coats of a high-quality, UV-resistant powder.
For more on how to spray two coats of powder, check us out on YouTube.
