Hot Flocking & Powder Coating – A Complete Guide
Hot flocking is a topic among powder coaters that is filled with a lot of different thoughts and sometimes confusion. Our goal here is to provide an overview of what hot flocking is, how it is done, and when it may make sense.
What Hot Flocking in Powder Coating Is
Hot flocking is the practice of heating up your parts surface so that you can shoot your powder coating onto a warm/ slightly hot surface which causes the powder coating to instantly begin to flow into its finished state.
How Hot Flocking Powder Coating is Done
As we mentioned hot flocking is done by heating the product surface up enough to cause the powder to instantly begin to flow as it is sprayed onto the parts surface. To hot flock you heat the product surface to a temperature that is above the curing temperature of the powder your spraying, the product surface must be hotter than the curing temperature of your powder coating so that the powder will flow as soon as it hits the surface. Prior to hot flocking the part you want to be sure that the surface of your part is clean, then you can set your oven and heat the part past your powders curing temperature. To know when your product has reached a temperature past your powder’s curing temperature you can use a infrared thermometer to measure the surface temperature from outside your oven. Once the surface temperature is high enough you will remove the part from the oven and can shoot the powder onto the surface. You will have to move quickly because the product surface must remain above the powders curing temperature in order for your hot flocking to work, if the product cools to much the powder will not stick to the surface and can create visual defects in your powder coating.
When Hot Flocking Powder Coating Can Be Helpful
Knowing what hot flocking is and how to do it, next it is important to understand when you may want to consider hot flocking powder coating. In general hot flocking helps overcome issues with powder applying well to a product. Often hot flocking is used for multiple coats of powder where there are issues getting the second coat on because of issues like back ionization or a general inability in getting the powder coating to wrap to the part because the part has reduced conductivity after a first coat of powder is applied or is a relatively non conductive surface like glass. Additionally, hot flocking can become more important when your applying a second coat of powder but do not have a professional level powder coating gun, meaning that your powder coating gun doesn’t allow 100 KV power or independent control of kilovolts and microamps. Having independent control of KV’s and microamps allows for easy application of multiple coats of powder coating.
Drawbacks to Hot Flocking When Powder Coating
While hot flocking can help overcome challenges with second coats of powder or lower quality equipment being used it does have potential drawbacks as well. First, hot flocking is hard to know how much powder your applying to the product. Since the powder is flowing as it is applied it can be easy to apply to much powder to your product which creates runs and a horrible finish, this will usually require you to redo your work. Second, it can be hard to ensure consistent even coverage of the part as you hot flock because powder that flows is hard to see visually, making it difficult to confirm if you have applied powder all over the part and if you have achieved an even coat.
How to Reduce the Need to Hot Flock Powder Coating
If hot flocking helps you achieve the results you need and has not created problems in your powder coating finishes then there probably is no reason to stop using hot flocking as a tool in your powder coating work. However if you have experienced some of the issues with excessive or uneven coats and want to try to reduce how often you hot flock in your powder coating, there are a few practical steps you can take. First, ensure you have the best possible grounding for your parts while powder coating. Often times if your having trouble with second coats of powder and similar issues it is because the part your powder coating is not strongly grounded (more on grounding and powder coating here). Ensuring a good ground will help with second coats because it can reduce back ionization issues (which is a common problem that hot flocking is used to fix). Second, you may consider upgrading your powder coating equipment. If your powder coating gun doesn’t allow independent control of kilovolts and microamps and is not rated for 100 KV’s of energy, it can limit your ability to apply second coats of powder. Between the two control of KV’s is most important, but best results with second coats can be achieved when both microamps and kv’s can be adjusted. In generally KV’s and microamps work in opposition of each other and when applying multiple coats of powder you will apply the first coat of powder at a higher kv with a low microamp and then slowly reduce kv’s while slightly increasing microamps after completing your first coat of powder coating, for more on spraying multiple powder coats check out our guide here. Upgrading your powder coating gun to a unit like a Wagner Sprint or something similar will allow you to independently control KV’s and microamps. If you have a fixed voltage powder coating gun you typically will have to hot flock your powder coating on second coats or faraday cage areas.
Final thoughts
Hot flocking powder coating can be a tool to help overcome issues applying second coats of powder and dealing with faraday cage areas. While it can be helpful it also does have potential drawbacks. If hot flocking ends up creating issues getting the finish you want in your powder coating, you can reduce the potential need to hot flock by improving your grounding source and/or considering improving your powder coating equipment if you have a fixed voltage powder coating gun.