Ask the Expert Question-and-Answer Archive

by Ron Joseph

November, 2005

Electrostatic Spray Guns and Spray Painting

Q. If the painted object can be insulated, is there any difference between having a high positive charge on the paint gun (an electrostatic spray gun) and instead put a high positive charge on the object to be painted? I realize there would be a shock hazard using the latter.

A. Many years ago Caterpillar tried to reverse the polarity of the painting process by doing something similar to what you have suggested. I seem to remember that the transfer efficiency improved significantly and that from a painting perspective it was very successful. They found that the new setup was extremely hazardous, because the entire machine had to be isolated. If I remember correctly, the charged part now became a huge capacitor. I don't know if they continued to pursue this concept, but I do know that I haven't read or seen this being done in practice since that time.

Best wishes,

Ron Joseph