Metal powder coating is a common practice. The powder coating enhances the metal surface’s resistance to chipping, fading, scratching, and wearing. Additionally, it protects the surface from environmental and weather factors.
So, it’s natural to wonder whether you can powder coat wood too. If so, does a powder coating offer the same benefits to wood surfaces? Let’s find out.
Can You Powder Coat Wood?
Yes, you can powder-coat wood. Indeed, powder coating is now used on various wood products, from solid wood to Medium Density Fiberboard (MDF) and HDF. It gives wood surfaces a new shine and enhances the item’s durability. However, beware that there are a few limitations to powder coating wood.
Advantages of Powder Coating Wood
Powder coating wood provides many of the benefits associated with powder-coated metal surfaces. Some of the advantages include;
- Cost-effective finishing
- It gives a stylish painted look
- Available in many colors
- It’s environmentally friendly
How Does Powder Coating Stick to Wood?
Unfortunately, coating wood is a complex process completely different from powder coating metal. Perhaps this explains why not all types of wood and wood products are ideal for powder coating.
Let’s begin with a few facts.
- Powder coating is electrically charged before application.
- You can only apply powder coating to a grounded electrical conductor.
- Dried wood doesn’t conduct electricity.
These three facts complicate the wood powder coating process. Specifically, how can you ground furniture for powder coating when dry wood doesn’t conduct electricity?
Perhaps one may argue that you can powder coat green wood boards and then dry them for furniture making. But is this practical? Anyone in the industry knows green wood shrinks and warps as it dries. The problem is exacerbated if you make furniture with green boards.
Worse still, a powder coating is a finish that seals the wood surface from the outside world. This makes it even more difficult to dry green boards.
So, what’s the solution?
First, you need to find sufficiently dry wood. But more importantly, you must test the boards or furniture to determine whether they can be grounded to facilitate the powder coating process. Fortunately, some solid woods and manufactured boards meet both criteria.
Factors to Consider Before Powder Coating Wood
The two main factors when powder coating wood are the properties of the wood and the coating powder type.
The wood you wish to powder coat must meet certain requirements for the highest powder coating results.
i. Surface uniformity
First, the item must have a certain level of porosity to accept the powder and surface uniformity. Uniformity here refers to surface characteristics like smoothness and temperature.
For instance, varying surface temperatures can cause inconsistent powder distribution. The same applies if the surface is not level. Therefore, you may need to sand down the boards before powder coating.
ii. Moisture content
Additionally, you want wood with consistent moisture content, as too much or too little moisture is bad. For instance, too little moisture creates conductivity issues, meaning the powder wouldn’t stick to the surface.
Meanwhile, too much moisture may cause poor curing, leading to low-quality results.
Many wood powder coating manufacturers recommend boards and furniture pieces with 5% to 7% moisture content.
Powder coatings are available in two main varieties – thermal cure products and UV-curable options.
i. Thermal-Cure Products
Thermal cure products are traditional coatings that rely on infrared ovens and convection heat transfer. First, the heat energy melts the powder, allowing it to flow into a level film. Then the film cures or cross-links into a finished layer.
ii. UV-cure Coatings
Meanwhile, UV-cure powder coating products allow you to separate the melt and flow processes from the curing process. Moreover, the curing process requires less heating.
First, the parts enter an infrared convection oven where the powder coating melts and flows. This process takes 2-10 minutes.
After that, the board is exposed to UV light for a few seconds, where the powder coating cures into a hard finish. Then it enters a cooling tunnel for a few minutes.
As you may guess, most people prefer the innovative UV-curing process. It’s a fast, 20-minute single-step process that happens at 220-240 degrees Fahrenheit.
Contrastingly, thermal curing takes 30-60 minutes and requires high curing temperatures up to 400 degrees Fahrenheit. Moreover, the cooling process for UV curing is much shorter.
How to Powder Coat Wood: A Step by Step Guide
Suppose you’ve decided to powder coat the kitchen cabinet doors for your next woodworking project. The following is a step-by-step guide for the powder coating process.
i. Wood selection
As we mentioned earlier, powder coating is not practical for all wood types. Indeed, only a few types of wood can be powder coated.
Oak, ash, walnut, and Sapele are the best candidates if you wish to powder coat solid wood. Meanwhile, MDF and HDF are your best options if working with manufactured wood products. Of all the candidates, though, medium density fiberboard (MDF) is the easiest to powder coat.
But more importantly, not all MDF projects are suitable for powder coating. For instance, a closer look at the most commonly powder-coated MDF projects reveals that wood powder coaters aren’t interested in “painting” flat boards.
Instead, they’re often looking for the best way to finish delicately detailed cabinet doors and routed table tops.
Additionally, you need higher MDF grades. We recommend boards weighing at least 48 lbs/ft-3, with an internal bond strength of at least 130 psi and moisture content of 5% to 8%.
If you’re on a tight budget or trying to save on input costs, it would be best to consider other finishing solutions.
In case you’re interested in learning more, here’s a guide explaining the differences between MDF and melamine boards.
ii. Surface preparation
Next, you need to prepare the wood surface for powder coating. Proper surface conditioning prevents poor grounding during powder application or outgassing during curing.
First, if the moisture content is out of range, you must store the substrate in a temperature and humidity-controlled environment until it meets the required moisture content.
Fortunately, you should be able to dry MDF boards to 5.5% moisture content within 12-24 hours by racking the boards in a way that exposes all the surfaces to the surrounding air.
Keep in mind that the moisture content requirement is a moving target dependent on local temperature and relative humidity (RH). Generally, you need the lowest moisture content (5.5%) at 50 degrees and 25% RH but require an 8.1% moisture content at 90 degrees and 50% RH.
Besides ensuring the required moisture content, remember that the substrate’s typography telegraphs through the coating. Therefore, you should sand down the surface if you desire a smooth finish.
iii. Apply wood primer
Wood primer is not mandatory. However, it can be valuable in many ways, just as when painting wood with liquid paint.
First, applying wood primer hides imperfections on the wood surface. This can be beneficial for no-sanded MDF boards. A coat of primer guarantees a more uniform finish devoid of valleys and bumps. It also hides joints and seams.
Additionally, raw wood primer prevents bleed-through from knots and conceals natural blemishes and coloring in bare wood boards. It also further protects the wood surface from external elements like weather.
Above all, wood primers boost adhesion. This quality is invaluable given the difficulty in powder coating wood.
Pre-heating may not be required depending on the properties of the substrate. However, it’s critical when powder coating MDF for the following reasons.
First, it allows the board to outgas before applying the powder coating, significantly reducing the risk of outgassing after the powder coating process. Secondly, pre-heating increases the electrical conductivity of the little moisture left in the substrate.
Finally, it boosts powder adhesion through impact fusion, which partially melts the fast-moving power particles on impact, a process known as impact fusion.
Remember to pre-heat to the lowest surface temperature at which electrostatic charge properties are optimized to avoid damaging the heat-sensitive substrate. This is very important as, unlike metal, wood easily burns at high temperatures. The ideal pre-heating range is 120 degrees to 140 degrees, though it varies from one substrate to the next.
v. Applying the powder
You can begin applying the powder once the substrate is pre-heated to the required range. Begin by grounding the wood. Then verify that it’s electrically neutral using a ground conductivity detector.
If it isn’t, use a liquid conductivity enhancer to improve the board’s conductivity and grounding properties.
Next, charge the powder coating and apply it to the grounded part of the substrate. The following are additional tips to observe;
- Ensure the powder is between 18-36 degrees Fahrenheit during application.
- Set the gun output to 170 to 210 grams/minute for optimal atomization, charge potential, and film control.
- Maintain an 8-12-inch distance to control pattern development and coverage.
- Optimize the voltage and current for maximum first-pass transfer efficiency.
v. Wood curing
Curing (drying) ensures the longevity of the substrate and creates an effective moisture barrier over the surface.
The three main thermal curing methods when powder coating MDF are via an infrared, convection, or combination oven. Many wood powder coaters use hybrid convection-infrared oven systems for greater speed and uniformity.
Moreover, hybrid ovens are more cost-effective than conventional ovens. Meanwhile, UV curing only requires UV emitters.
Always follow the substrate’s technical data sheet requirements and contact the manufacturer if you feel lost.
vi. Cooling, de-racking, and final inspection
Typically, the substrate cools as it exits the oven. Verify that the temperature is comfortable enough for handling and packaging.
Further cooling at room temperature is also necessary for chemistries incorporating thermoplastic components requiring a MEK or cross-hatch. Testing these elements before the substrate dries fully may return a failure.
Misconceptions About Powder Coated Wood
Though powder-coated wood finishes have been around for a while, there are still a few misconceptions about the topic. So let’s burst some of those myths.
- Powder-coated wood is not as durable as other finishes: This is a lie. For one, powder coats provide a tough 5-7ml bonded coverage. More importantly, it bonds to the surface without adhesives that may fail or form bubbles. This makes powder-coated finishes almost as durable as laminate finishes.
- Powder coating is not cost-effective: There’s a common misconception that you need large runs of a single part for powder coating to be effective for woodworking projects. This is false as powder coating spray booths attached to CNC machines guarantee increased throughput.
- There’s a limited choice of colors and gloss levels: This claim is misleading. On the contrary, there are limited color choices. Indeed, powder coaters can form custom color formulations depending on the customer’s needs.
- Powder coating is a cheap wood finish: Unfortunately, earlier powder-coated wood products had surface imperfections and thin coverage that led to the misconception that all powder-coated wood products are low quality. Not anymore. Today’s powder-coated wood products are even more expensive than melamine and in the ballpark of high-pressure laminate (HPL) products.
How Long Does a Wood Powder Coating Finish Last?
Powder-coated wood finishes can last up to 40 years, depending on the type of coating, surface preparation, treatment, and product maintenance.
Over this period, powder-coated wood exhibits excellent weather resistance and can take high traffic without fading or showing signs of wear.
Best Woods to Powder Coat
The best woods and wood products to powder coat are oak and ash (if interested in solid wood) and medium-density fiberboard (MDF), and high-density fiberboard (HDF) if you’re interested in engineered wood products. MDF is the best among the four.
Best Powder Coaters for Wood
BTD Wood Powder Coating and Keyland Polymer UV Powder Coating Products are the best wood powder coaters. These companies will happily powder coat your wooden boards on your behalf.
Alternatively, you can purchase powder coating products from PureClad or Akzo.
Powder coating is now a practical wood finishing solution for selected wood types and manufactured wood products. It offers several benefits, including enhanced board durability, weather resistance, and corrosion resistance.
Above all, wood powder coatings are available in a wide range of colors for a unique visual outlook. Therefore, you should strongly consider it for your next project.