Q: We are trying to develop a specification for our powder coated products. Coating thickness varies from product to product and from color to color. I am trying to determine the range of film thicknesses I should specify. Are there any guidelines for film thickness for powder coating operations?
A: Yes, there are some resources to help you determine the correct film thickness. First, check the powder supplier's Technical Data Sheet (TDS), which should include a suggested film thickness range for that particular powder. The range can be quite wide, like 1.5 to 3.0 mils, but it will give you an idea of how the thickness range works. Coating thicknesses within this suggested range will provide the listed performance characteristics and will avoid undesirable appearance characteristics such as excess orange peel.
Another key consideration is the performance you expect and the environmental conditions the part will be subjected to in end use. A final factor to consider is the nature of the substrate being coated. The shape and texture of the part will affect how much thickness is needed and how much control you have over the overall average.
Try to determine the minimum film thickness based on the hiding power of the powder and the desired properties. TDS is a good source of guidance for parts that have a clean, smooth surface that will not be subjected to harsh environments. Typically, a thickness of about 1.5 to 2.0 mils will work well. The more geometry you have on the part, the more variation you can potentially have because part shape affects the uniformity of the film.
For parts that need to handle harsh environments, you may need more film thickness. Outdoor performance requires a thicker minimum, so the average film build is thicker, say 2.5 to 3.5 mils. If the surface is rough or blasted, a higher average is required to ensure adequate coating of the peak area. For extreme environments or very high performance, you may need two coats. Keep in mind that edge coverage is moderate with only one coat, a second coat will provide better edge protection. Also, a primer will provide a better moisture barrier. With a primer and topcoat, the total thickness can be 4 to 6 mils.
There is no one-size-fits-all thickness. Check the TDS, consider the desired performance, look at the substrate and you should be able to come up with the correct spec.
