High-Temperature Powders

Question:

I saw your answer regarding high-temp powders and your offer to help, so I was hoping you might be able to offer some assistance to me as well.

We are making a barbecue grill that we will sell as an incentive/promotional item. As such, we need lots of colors. The max temp the metal (currently aluminum) can reach is about 600°F without any insulating coating. If we use a ceramic-based insulating coating, then that reduces the temp to about 350°F.

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A couple of questions if I may:

1. If we stay with the ceramic coating, do we need to stay with silicone-based coatings to withstand the heat?
2. How flexible are the color choices in a high-temp powder? We know we can get all the colors we want with porcelain, but that would require us to change our design to steel—which means an appreciable increase in weight.

Thanks for any information that you can provide. P. B.

Answer:

Most standard powder coatings will degrade under regular use where heat conditions are above 250°F. Therefore, you will have to use a high-temperature-resistant powder coating for long life. The mechanism of failure for powder coatings used in high- temperature applications will be color and gloss shift, followed by embrittlement and finally complete failure by cracking and loss of adhesion. When this failure occurs depends upon how much temperature the part sees and for how long it sees it. As for your question on color selection in high-temperature powder formulations, you should check with a supplier of these materials. They are available in many colors, but are not available in white or very light colors. This is mainly due to the stability of the pigments used in making these powders. Obviously, black is most commonly used in high-temperature applications.