Quality control of coating powders
Powder coating of metal products, for example, on aluminum extruded profiles, is a complex technological process. To ensure the high quality of powder coatings, it is necessary to keep a large number of technological parameters in optimal intervals at all stages of production: from preparation of the surface of the product for painting to the exit of the finished painted product from the polymerization oven..
Powder Coating Defects
Sources of Powder Coating Defects
A nightmare of a powder coating technologist - massive defects on an already finished powder coating. Many defects can have several reasons for their origin.. Quickly identify and eliminate the cause of such a defect, or even more than one - not an easy task.
The most common cause of these defects is a violation of the technological parameters of coating:
- dust and other contaminants from the ambient air or oven atmosphere
- poor compressed air quality
- insufficient surface preparation
- violations of electrostatic powder spraying technology
- violation of heating parameters in the polymerization oven.
When compressed air and all process parameters are in order, there is not a single speck of dust in the powder coating area, but defects still "don't go away", it's time to check:
- powder paint quality, which is applied to the product.
craters
for instance, powder coating defects such as "craters" can appear for many reasons, such as insufficient surface degreasing or excessive oil in the compressed air. However, another cause of craters may be the mutual reaction of two incompatible paints, who inadvertently ended up nearby in the spraying equipment.
Shagreen
Another example might be the "pseudo-crap" defect. It occurs due to a too thick powder layer, violation of the heating parameters of the product in the polymerization oven or, the so-called, reverse ionization by electrostatic powder spraying. At the same time, another reason for this defect, more rare, may be a violation of the recipe composition of the paint, which led to insufficient flow of the paint before curing (polymerization) or its premature curing (polymerization).
Inclusions
However, without a doubt, the scourge of powder coating technologists is such a defect in powder coating, as "inclusions". In English it is called "bits" or "seeds". These are small foreign objects visible to the naked eye., particles not melted in the furnace, which are usually completely or partially covered with paint. Often they really, similar, on the smallest seeds scattered They appear as if from nowhere and often leave by themselves. They appear after, how the coating is "baked" and comes out of the oven. By this time, it is already too late to do something to eliminate them and there is nothing left but to completely repaint the finished painted products or send them to scrap.
"Habitual" causes of powder coating defect "inclusion" are insufficiently cleaned, "dirty", compressed air or foreign particles and airborne contaminants in the powder coating area, as well as at the entrance to the polymerization furnace.
A more hidden cause of the "inclusion" defect may be the problems of the powder paint itself., such as contaminated starting materials, prematurely polymerized particles, large agglomerates of particles of additives and others.
What is "powder paint quality"
When solving problems with the quality of powder paint, many questions arise., including:
- What are the indicators of the quality of powder paint?
- How do these quality indicators of powder paint affect electrostatic spraying technology?
- How does the composition of powder paint affect the quality of the finished coating?
- What test methods are used to control the quality of powder paint?
Quality control of coating powders
All, who in one way or another works with powder paint and faces problems with:
- powder paint production
- supplying it to consumers
- ordering paint for our own paint production
- powder coating of their products "on the side"
- transportation of paint from the manufacturer to the place of its application
- input and periodic quality control of powder paint in the paint production
- storage of paint in the conditions of paint production
- industrial powder coating
- identifying the causes of defects in powder coatings in the paint production
- development of measures to prevent powder coating defects.
To be continued
