How to Prevent Orange Peel in Powder Coating – A Guide
Orange peel is when the surface of a coated product doesn’t have an even smooth appearance to it after the coating is applied. Whether your powder coating or liquid coating, orange peel is usually not desirable because it creates a poor overall finish appearance when your all done coating your product. Knowing orange peel in powder coating is not ideal, it is important to know some of the reasons why it happens and how you can reduce the chance of having orange peel in your powder coating.
Why Orange Peel Happens in Powder Coating
When it comes to orange peel in powder coating, there are a few primary categories for why it occurs. First, is the way the powder coated surface is prepped prior to being powder coated. Second, is how the powder coating is applied. Third, is how the powder coating is cured after being applied. Each of these areas, when not properly completed can result in orange peel in your powder coating. Will cover how each area can result in orange peel.
Surface Preparation and How it Can Contribute to Orange Peel in Powder Coating and How to Prevent Surface Preparation Contributing to Orange Peel
Prepping a surface for powder coating can be done in two main ways, chemically through phosphate or zinc immersion or mechanically through sandblasting. Sandblasting generally produces greater durability of a powder coated part but also creates indentations in the surface, which help the powder coating adhere to the surface. The one problem with a sandblasted surface is that in some cases it can contribute to orange peel after you have finished powder coating the part. Sandblasting is most likely to be a potential source of orange peel if the surface indentation is to deep which can cause you to have to apply to thick of a layer of powder coating or if not powder coated enough can cause the indentations to stand out above the actual powder coating. Some examples where surface preparation may be causing orange peel in your powder coating include when your powder coating chrome surfaces and other surfaces that tend to appear polished or need to appear polished after powder coating. If you find orange peel occurring when powder coating these kind of surfaces, you can try a few things to address orange peel happening. First, you can try to sand the sandblasted surface with a 300 grit or finer sandpaper, this will reduce the depth of the profile the sandblasting created. Second, you can try a different sandblast media that will not create as deep of a blast profile. Third, you may want to consider applying a powder coating primer prior to your final top coat of powder. All of these tips can help ensure the surface preparation does not contribute to orange peel in your powder coated finish.
How the Powder is Applied, How it Can contribute to Orange Peel, and How to Prevent Orange Peel related to Powder Coating Application
A second common cause of orange peel in powder coating is how your powder coating is applied. Specifically, how much powder coating is applied. Powder coatings typically have a technical data sheet which will specify a minimum and suggested amount of powder coating that should be applied. In general if you apply significantly more powder than the sheet recommends, this can potentially cause orange peel because the powder will not cure smoothly when it is being baked. Orange peel can also occur if you do not apply enough powder coating. To prevent orange peel due to excessive powder coating application, you can use a tool to measure how much powder coating has been applied. The goal is to apply the powder in the recommended thickness but not to apply to much or to little. Options for measuring powder coating thickness prior to cure include a powder comb like this and the PosiTector-PC unit , the powder comb is the more cost effective option. In addition to how much powder is applied, you also want to ensure you apply the powder using proper settings on your powder coating gun with a good ground. The technical data sheets for powder coating generally provide gun setting recommendations which can help ensure best results. A good ground ensures your powder is applied effectively, which you can read more on grounding and powder coating here.
Below is a technical data sheet for powder coating that shows recommended application settings and cure schedule.
How the Powder Coating is Cured and How it can Potentially Cause Orange Peel, Plus how to Prevent Orange peel from Curing Issues
A final potential cause of orange peel when powder coating is how the powder coating is cured. Powder coatings have recommended cure schedules where temperature and time recommendations are provided. These cure schedules are designed to enable the powder coating to flow out most effectively, which leads to a smooth finish. If you try to cure the powder coating faster than is recommended or can not heat the product to the recommended temperature, then you may get orange peel in your powder coated finish. This is because the powder may not fully flow out and link together to enable a smooth finish. Powder coatings will generally have a recommended cure schedule in there technical data sheet which you should follow. You can use an infrared thermometer prior to using your powder coating oven to verify that your ovens temperature is set to the recommended powder coating temperature. If your oven is hotter or colder it can cause poor flowing of your powder coating which can result in orange peel.
Ultimately your goal when powder coating is usually a smooth professional appearance. In order to get a smooth finish and avoid orange peel, you have to ensure the surface has been prepped well without an excessively deep or shallow profile, that the powder has been applied properly without too much or too little applied, and that the powder coating is cured properly. By following these steps you will be most likely to achieve a smooth powder coated finish.