Ask the Expert Question-and-Answer Archive

by Ron Joseph

May, 2003

Wet Spray Booth for Powder Coating

Q. Can you use a wet spray booth to powdercoat?

A. I presume that you are using a dry filter spray booth but are spray-applying liquid coatings in that booth. Is this correct?

In principle you can use a dry filter spray booth in which you paint with liquid coatings, to also apply powder coatings. However, there are several points you should consider:

1. You should use filters that are intended for applying powders. If you use the same filters as for the liquid paints, you might find lots of powder escaping through the filters and going up the exhaust stack. This can cause excessive powder to deposit on the fan blades and eventually the motor can burn out. Moreover, if you mix liquid and powder coatings in the same booth, the powder can settle inside the exhaust stack and on the fan to form a thick heavy deposit .. not a good idea.
2. If possible, you should not use both liquid and powder coatings in the same spray booth. I have seen situations in which the filters have been thoroughly caked over by the mixture of liquid paint and powder particles. I also mentioned another disadvantage in the previous paragraph.
3. The overspray from the liquid paints that settle on the walls and floor of the spray booth can easily contaminate the powder coating application. In other words, when you bake out the powder you will find dust particles from the overspray in the baked coating.
4. You will not be able to collect the waste powder, (in other words, the powder that does not deposit on the workpiece) and recycle it, because there will be too much dust and dirt in the coating.
5. Insure that you have a proper working sprinkler system in the booth so that in the case of a fire, the sprinkler will immediately operate.