Powder coating on alloy items and outgassing;

Although we strive to provide the best possible results, there are some essential factors you should be aware of before proceeding. Powder coating requires curing at least 180 degrees Celsius, which can cause certain metals and castings to undergo chemical reactions. For example, porous materials such as Ali alloys, magnesium, and some cast irons may release gas or air trapped inside microbubbles during oven curing. This can create tiny bubbles under the cured powder coating, often mistaken for poor prep work or contamination. These bubbles are caused by outgassing, which occurs when the trapped gas expands and pushes its way out of small holes or microcracks in the coating. This problem can be mitigated by reworking the parts or using an anti-gassing product, although this does not always work. In the case of poor-quality castings, nothing can prevent outgassing other than using wet paints and suitable fillers. 

In addition to outgassing, corrosion can be a problem with certain alloys and cast irons. Even with careful prep work and media blasting to remove corrosion, micro-holes may be left behind, leading to outgassing. Fillers are not typically used for powder coating as they can burn or expand, but high-temperature fillers may be used in some cases of corrosion. 

Outgassing is caused by entrapped gases being released during the curing process, which can create pinholes in the coating. This can lead to moisture or corrosive materials penetrating the coating and causing it to fail. Outgassing can be attributed to the substrate material, surface contaminants, or powder. Castings and zinc-coated substrates are particularly susceptible to outgassing, as are heavy coatings applied in a single layer. Some types of coating are more likely to cause outgassing than others. Unfortunately, if outgassing occurs, we are unable to offer any guarantees.

M.D.