Powder paint quality check: what to focus on

In order to get a quality cover, it is not enough just to buy paint and equipment. Even the most experienced specialist cannot make a good coating with low-quality paint. Defects will appear and that is supposed to be corrected. Poor quality paint is also one of the reasons powder paint peels off.

Therefore, before paint proceeding check the quality of the powder.

Testing the quality of a powder paint primarily consists of controlling the flowability, curing time, particle size and powder density.

We strongly recommend buying paint only from trusted manufacturers with appropriate certificates. This will protect you from low-quality products and, as a result, disappointment in powder coating.

It is also impossible to store the powder for a long time. Their composition may change over time.

How to check the quality of powder paint

1. Start testing with flowability. Good paint can be easily poured and transported by air. You can check how long it takes for the powder to flow out of the funnel with different nozzles. This should happen pretty quickly. Flow problems are especially noticeable if you have already used quality paint and you know how long it takes it to pass this way.

This characteristic can be checked by the repose angle of poured powder on a horizontal surface.

2. Check for volatile substances in the paint: moisture or other additives. Weigh the paint, then dry it in the oven and weigh again. The loss of weight in paint means that it has managed to gain moisture or other volatile substances in its composition.
3. Then proceed to control the polymerization time. It allows you to determine the reactivity of the powder. Count seconds during different temperature regimes for the paint to melt and begin to cure. By performing this test regularly, you can monitor the stability of the powder during storage. The polymerization time can be measured in a polymerization oven. Install the glass plate, tilting it slightly, warm it up and place the powder tablet. Then measure how strong the tablet melted. If during regular checks you notice a decrease in the trace, this means that the powder has expired.

The spreading of the paint is checked visually. It should always be relatively the same. Significant changes indicate deterioration of the paint.

The better the paint spreads, the smoother the cover will be. And vice versa, poor flow results in a structured cover – an “orange peel” effect.

Spreading improves as the coating thickness increases or the temperature rises.

4. After examining these parameters, proceed to the study of the particle size of the powder. It is very easy to measure them. It is necessary to pass the paint through a series of sieves with different holes and measure how much material is retained in them. You can measure their characteristics with more sophisticated devices. They determine particle size by methods based on light scattering or electrical measurements.

Types of defects in powder coating

Bad paint will definitely affect the quality of the paint.

You may encounter:

• “Dirt” and mechanical inclusions on the surface of the part
• Ripple
• Absent or too small coating thickness, “unpainted” in some places
• Small round, through, or very deep holes in the coating
• “Craters”
• Bubbling
• Changes in the color of the powder coating
• Smudges
• Fine mesh of cracks
• “Waviness” (different coating thickness)
• Poorly visible pattern
• Peeling coating

For excluding these problems, be sure to use only high-quality paint from well-known manufacturers, which has all the confirming quality certificates.