Evaporative Coolers for Fluoropolymer Coatings

Question:

My company is building new powder coating facilities for fluoropolymer coatings. We’re in a dry area of the country, and it has been proposed to use evaporative coolers rather than refrigerated air conditioners for the plant mechanical system (environmental, not compressed air). My coating supplier can’t give me any definite specs for what humidity is unacceptable. They just say that more humidity causes more coating problems. Do you have any experience that can help us decide whether evaporative coolers are acceptable for fluoropolymer coatings? P. R.

Answer:

Personally, I don’t care if people use ice cubes and a fan to control their powder coating room environment, as long as they control it within recommended limits. However, the particular details you requested are as follows: temperature control between 65-85°F and humidity control between 40–60% RH. However, what can create real havoc in a powder coating system are drastic changes in temperature and humidity over a 24-hour period. For instance, if the temperature and humidity start out the day at the lower limits and reach the higher limits at the end of the day, your powder gun settings and powder storage will both be adversely affected. Therefore, temperature and humidity stability throughout the day (and within the stated limits) is very important. The temperature and relative humidity limits are specified for min/max levels over an entire year, not within one day.

Lastly, if you are in a “dry climate” re-humidification (adding humidity into the room) may be required to keep the relative humidity above 40%. Too dry of an environment can cause major problems with Faraday areas, recoats, back-ionization, and thicker coats, especially using fluoropolymer powder coatings.