In this guide we will cover how to effectively apply powder coating to your product. Prior to applying powder, be sure that you have properly cleaned and pretreated your product, which you can review in our previous guide here. After you ensure that your product has been properly prepared by profiling or etching, cleaning, and outgassing (if required), you can proceed to apply your powder coating. To achieve the best results, follow the advice below.
Tip 1: For Best Results Applying Powder Coating – Understand Your Powder Coating Gun Settings
Powder guns offer different levels of settings to control how your powder coating applies. Budget guns like the Red Line EZ 50 and EZ 100 are in the $400 – $600 range and allow for adjustment of KV only. Industrial guns like Wagner Sprint systems allow adjustment of KV, microamps, powder to air mix, and even how fast electrical changes occur as you get close to a part’s surface. We will cover each of these settings briefly so you can better understand how each one will help control your powder coating application.
Kilovolts (KV) – 1,000 volts
Kilovolts is how much voltage (or electrical charge) a powder unit can produce. Industrial units offer 100 KV while budget guns will range between 25 and 100 KV. Higher KV provide the maximum potential wrapping effect of powder coating and are best for flat parts and first-pass coats. If your product has a lot of corners, you will typically want to reduce KV. For flat parts, KV in the 75 – 100 range is often common. In cornered areas, you may only use 25 – 50 KV. For multi-pass powder coating projects you usually start with KV on a high setting (75 – 100) and drop down to a lower KV (40-50) on the second coat. You will also want to limit microamps so that excessive voltage is not applied to the powder. Otherwise, it can create issues like back ionization (explained below). If you find that you have consistent trouble getting good results with your powder gun and it is a budget or entry level gun, it may be because the gun does not change KV and microamps together. Industrial equipment like the Wagner Sprint systems adjust both voltage and current (measured in microamperes) to ensure that the desired energy is consistently provided to your powder. Budget guns do not automatically adjust KV and microamps, which may result in difficulty getting sufficient powder in corners or on second coat work (unless you use a trick like “hot flocking” your second coat).
Microamperage (µA) – commonly referred to as microamps
Microamps is the current that your powder coating gun is producing. Not all powder coating equipment will allow you to control microamps. Microamps and KV work through an inverse relationship. KV is the potential energy available, while current is how much energy is actually being used – as current increases, less energy is left to do work. This is important for Faraday cage areas and projects with second coats since you generally want to ensure that KV do not become excessive. If they do, your powder will have trouble covering on a second coat or reaching the corners. That is why industrial equipment will allow you to set the microamps. This feature sets a limit to how much current can be used prior to KV beginning to reduce. By limiting how much energy is at work, you will be able to prevent issues where too much voltage builds on a surface – which is what causes back ionization. You should also ensure that excessive voltage is not applied to your powder coating when you are close to parts or trying to powder coat corners. For Faraday and second coat work, you generally want the microamps to have a limit of 20 – 40. If your gun does not allow adjustment of microamps, you can help overcome some of these problems by (1) using a lower KV setting, (2) increasing your distance from the part, and/or (3) heating the first coat to help the second coat stick with greater ease.
Powder to Air Mix
If your powder coating gun allows you to control powder to air mix, it can be tremendously helpful in getting the results you want. A common mistake is using an excessively rich powder to air mix setting. You do not typically want to go above 60 – 70 for your powder to air mix. For Faraday, intricate parts, and second coats you will often find a setting of 40 – 60 may be best.
Tip 2: Shooting Powder
Prior to Beginning
As we mentioned at the beginning of this article, proper preparation of your product surface is critical to ensure a good result. By following our guide on prepping surfaces for powder coating you can be better sure your surface will be properly profiled and clean.
Shooting the powder coating
By understanding the settings discussed above, you can ensure that you have set your powder gun to provide the best results. You may want to review the type of nozzle you are using with your powder gun – most will have tips for round spray patterns and flat fan patterns. For most applications, a flat pattern will work, however, if you have small parts, a round pattern may help reserve powder. Before shooting powder at the part, briefly shoot the powder gun away from your product to ensure your powder is flowing consistently. To apply the powder coating, keep your powder coating gun about 7 to 8 inches away from the part (unless you are dealing with Faraday or second coats with a lower cost gun, then consider increasing your distance a bit more). Move the gun back and forth across the part and aim to cover the part in a single pass. Keep the gun a uniform distance from the part’s surface. After you have applied your powder, review the work with a flashlight. Be sure to check that all areas have a good coat of powder on the surface to make sure that you have even coats of powder and won’t end up with certain areas rusting due to poor coverage.
Tip 3: Common Powder Coating Application Problems
Not Enough Powder in Areas
If you notice that you were unable to get enough powder in certain areas of your part, then you may need to do one of three things:
- Verify that your parts and equipment are well grounded (you can learn more on grounding your parts for powder coating here). If you have a good ground, then most likely you need to consider adjusting your powder coating gun settings.
- Common setting changes include increasing KV for flat parts without corners, decreasing KV for parts with corners or for second coats, and increasing powder to air mix.
- If you routinely find that these suggestions don’t work with a budget powder coating gun, you may want to consider upgrading to an industrial powder coating gun for optimal results.
Orange peel is when your powder coating appears chunky and not uniform in areas. Orange peel will happen when too much powder is applied in a given area or when your powder is not cured long enough. If you are coating parts with many corners and find that orange peel is occurring, consider reducing KV and reducing powder to air mix. Similarly, if you have the issue on flat parts, consider reducing the powder to air mix.
Back ionization typically happens on second coats and appears like small “star bursts” in your powder as you apply it. Once cured, it will have a larger burst appearance. This issue is due to an excessive KV charge on your products surface. To fix issues with back ionization, you need to improve your ground then consider limiting microamps and/or reducing your KV. This will help reduce the amount of charge you are applying.
Ultimately, understanding how to set your powder coating gun and how to use it will allow you to achieve smooth, fine appearing finishes in your powder coating. You can call us anytime for additional help with powder coating.