How to avoid bubbles and porosity on powder coating applied to a cast metal surface

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Powder coating is a technique that provides an extremely durable coating. However, defects such as bubbles, pinholes, craters, or porosity can occur and, in addition to spoiling the coating’s aesthetic appearance, they can compromise its functionality, quality and durability over time. There are several reasons for these defects, but they can be avoided with a few tricks.

Substrate preparation

It is essential that the substrate is clean, dry and free of any contaminants before applying powder coating. This is especially true for exhaling substrates, such as steel castings, galvanized steel, aluminum and its alloys, as these metals can release entrapped gasses during curing. To achieve a clean and smooth surface that facilitates the coating film’s adhesion, removing all traces of oil, grease, rust, or other residues from the substrate is necessary.

Environmental conditions

Environmental conditions also affect the result of powder coating. If the environment where the application is done is too hot or too moist, this can create adverse conditions for the application.

The best conditions for application are a maximum temperature of 35°C and Humidity between 20-70 %.

Powder coating selection

Once the substrate has been prepared, the selection of a suitable powder coating becomes critical.

To achieve the best results on this type of substrate, it is important to use a quality powder coating that promotes outgassing and allows the entrapped gasses in the substrate to escape.

RIPOL’s OGF Series consists of powder coatings based on polyester resins (topcoat, single coat) and epoxy or epoxy-polyester (primer), formulated with enhanced outgassing characteristics for applications on exhalant substrates. These coatings are designed to mitigate the expulsion of gas during the powder coating curing process, preventing the generation of bubbles and promoting an optimal aesthetic result.

The OGF polyester series also offers excellent weathering, UV and good chemical resistance.

Coating Application

Finally, to achieve good coating distribution and adhesion, air pressure, electrostatic tension, distance and spray angle must be carefully adjusted, remembering to apply the coating in thin, even layers.

By carefully following all these steps, the powder coating will result in a smooth, homogeneous, defect-free and durable finish capable of meeting aesthetic and functional customer needs.

We encourage you to contact us for any questions or concerns about powder coating.