Electrostatic painting of nonconductive surfaces with water-base paints

Electrostatic corona painting on nonconductive surfaces normally requires a ground-connected conductive precoating of the surface in order to dissipate the continuously incoming ionic charge from the corona gun. If the surface charge does not flow to ground, the resulting surface electric field will repel a substantial amount of the incoming paint. The authors present a new painting method consisting of generating ultrasonically atomized electrically charged water particles behind the nonconductive surface to be painted. The paint spraying is carried out with a mechanical spray gun maintained at ground potential. The water base paint becomes charged by induction under the influence of the space charge behind the nonconductive surface to be painted. As the resulting charge on the water base paint particles is of opposite polarity to that of the ultrasonically atomized electrically charged water particles cloud, all propelling electric fields converge toward the surface to be painted. The results show excellent transfer efficiencies.