If the gas is not vented from the metal before powder coating, problems such as bumps, bubbles, and pinholes may occur. Image source: TIGER Drylac
In the world of powder coatings, cast metal surfaces such as iron, steel, and aluminum are not always tolerable. These metals trap gas pockets of gases, air and other contaminants in the metal during the casting process. Before powder coating, the workshop must remove these gases and impurities from the metal.
The process of releasing entrained gas or pollutants is called degassing. If the store is not properly degassed, problems such as bumps, bubbles, and pinholes will result in loss of adhesion between coatings and rework. Degassing occurs when the substrate is heated, which causes the metal to expand and expel trapped gases and other impurities. It must be noted that during the curing process of powder coatings, residual gases or contaminants in the substrate will also be released. In addition, gas is released during the process of casting the substrate (sand casting or die casting).
In addition, some products (such as OGF additives) can be dry blended with powder coatings to help solve this phenomenon. For cast metal powder spraying, these steps can be tricky and take some extra time. However, this extra time is only a small part of the time required to rework and restart the entire process. Although this is not a foolproof solution, using it with specially formulated primers and topcoats can help alleviate outgassing problems.
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