How to eliminate powder paint defects
Powder paint is a paint material that better cope with the negative external influences. It has less noticeable traces of operation. And the coating turns out even and without leaks. If the technology of applying the powder to the product is adhered, the coating can last up to 20 years. But often painters face some painting problems.
Today’s article is dedicated to powder coatings, defects and the analysis of their causes. And also tell you how to fix them.
Defects in powder coatings
So, let’s see what defects are most commonly encountered:
- “Clogging” and mechanical inclusions. Alien particles, debris, fibers and more are visible on the coating.
- Surface relief (shagreen where it should not be).
- The coating thickness is too small, in some places powder doesn’t settle.
- Holes of different shapes and depths.
- Round depressions, craters.
- The “boiling” of the coating, the formation of bubbles.
- Spotting, changing the color of the paint in some areas.
- Leaking, thickening.
- A fine mesh of cracks all over the surface.
- Poorly pronounced drawing.
- Gas sinks: openings with exfoliation.
Removal of powder paint defects
Now let’s talk about how you can get rid of problems that have arisen:
- Clogging. Sift the paint or look at it through a microscope. If the paint itself has foreign particles, it must be replaced with another. If the paint is OK, clean the feeder and the recovery system. Look for impurities in the means used to prepare the products for painting.
- Shagreen. Look expiration dates on the packaging of powder. Use only good paint. Check the thickness of the coating. If it is large, adjust the powder supply, reduce the voltage or spray time. Check the paint approval guidelines and see if the spraying chamber meets the requirements. Pass the powder through sieve No01. If more than 0.5% – 1.0% of the powder is left over, change it or increase the thickness of the application. It is advisable to remove large particles.
- Insufficient thickness. Look for instructions on whether the gun works properly: voltage, spray time, powder supply. Check the grounding of the painted product. Clean the suspension if necessary.
- Puncture. Check the moisture content of the powder, storage conditions and transportation conditions. See what moisture is in the powder from the feeder. If necessary, adjust the compressed air cleaning, replace the absorbent, install the filter. Make sure the product is completely dry after cleaning. Try to make less time between preparation and application of paint. If the painting of the sheet steel is normal and the cast and thick-walled surfaces have problems, then the last products should be warmed up before painting.
- Craters. Make sure the air is clean properly. Replace the required items. Try different paints. When replacing the paint with a new one, clean the spraying chamber, sprayer and all items thoroughly.
- The boil. Reduce the thickness of the coating. It is better to degrease the part before applying the paint, especially in hard to reach areas. Try warming up the part before painting. Remove the previous coating completely.
- Stains. Measure the temperature in the polymerization furnace and check its uniform distribution. Adjust these figures as needed. See if the recommendations meet the baking time.
- Leakage. Adjust the spray pressure and voltage. Reduce powder application time. Look at the baking temperature for instructions and make sure the oven is set to the correct temperature. Try different paints.
- Cracks. Make sure the baking mode meets the guidelines. Try baking the product longer.
- Waves. Adjust the position of the pistols, select the appropriate nozzles. Change the position of the part.
- Bad picture. Increase powder application time and thickness. Adjust position of the gun and the part.
- Gas sinks. Check the temperature in the oven, its uniformity, baking time. See if the product is degreased well before painting.
- Peeling. Make sure that the surface is degreased, remove oxides. Try to etch the product if you have not done so before. Adjust the phosphate and chromate layers. Check the polymerization modes for compliance. Increase baking time.
These are the main types of powder coating defects. Sometimes there are specific problems. And they will only be eliminated by a specialist.