Surface microstructure of powder layers influenced by the forces of deposition and adhesion in electrostatic coating process

In the electrostatic powder coating process, several Factors affect the dep osition of charged polymer paint particles and the adhesion of the deposite d particles on the grounded substrate being coated. In this paper, the role s and relative magnitudes of these forces are discussed. A model on the dep osition of a charged particle approaching the surface of the substrate is p resented, The electrostatic Fields that are considered here to be responsib le for particle deposition are the following: 1) corona field between gun t ip and grounded plane; 2) image field between a particle and its image char ge; 3) field due to the space charge of charged particles; and 4) net repul sive held between a charged particle and the powder layer. Once the particl e deposits on the surface and the high voltage is turned off, the particle experiences the following forces: 1) the force due to the image charge of t he underlying powder layer; 2) the force due to the image charge of the par ticle; and 3) the repulsive force between the charged particle and the char ged powder layer The model shows criteria on whether the particles will dep osit on the substrate and, if deposited, whether they will remain on the su rface of the powder layer once the corona field is turned off, These relati ve forces influence the microstructure of the powder layer and may affect t he ultimate appearance or the texture of paint film after curing.