To achieve fantastic looking powder coated parts, the powder coating application must be done according to the prescribed application guidelines. One of the essential parameters that needs be followed is the applied film thickness. It can be measured with proper equipment (film thickness gauge). To achieve an optimum effect and reduce voids exposing bare metal, a general recommendation is that powder coating is applied at a minimum film thickness of 2.5 – 3.0 mils. However, film thickness variables may also include chemistry and formulation of powder coating, the opacity of the color and the substrate type, just to mention few. Keep in mind that shortcuts in the powder coating process can lead to complications regarding film thickness. Always check powder coating Product Data Sheets to ensure the best practices for coating thickness and cure oven conditions.
There can be many issues if the film thickness is either too low/thin or too high/thick:
None of these issues result in a flawless finish and a happy customer, therefore it is critical to ensure quality control of film thickness during the application process. Thickness is typically measured after-curing. There is a variety of handheld instruments available, depending on the substrate.
Dry film thickness (DFT) instruments are the most popular amongst powder coaters as they are simple to operate and do not damage the surface finish. Depending on the substrate, different operations are preferred:
- A magnetic principle is used on steel parts
- An ultrasonic principle is used on non-ferrous parts
Customers commonly use coating thickness gages to verify the specifications on products received from Job Shops, so it is important that powder coaters consistently record quality control data in case it is requested. While collecting data may seem like an additional expense in measurement equipment and an extra step in the process, it invariably leads to fewer customer complaints and increases the quality reputation of the powder coater. You do quality work – back it up with data!