Modeling of electric fields during electrostatic coating of metallic substrates in fluidized beds

Electrostatic powder coating in fluidized beds is a technique that has been known for more than 30 years. The present paper attempts to model the changes in the electric fields produced by the progression of the powder coating layer on the surface of a metallic wire substrate immersed in a fluidized bed of charged powder. The intersections of wire geometries often present coating difficulties due to Faraday cage effects. The current modeling shows that as powder deposits on the substrate on areas where the electric field is strongest, the electric field is enhanced in the original weaker areas thus promoting powder deposition towards the intersections. Also, the effects of varying the size of the fluidized bed are investigated and show that as the bed size increases, while the substrate size remains constant the electric fields in the bed increase significantly; however, the electric field enhancement at the intersections of the substrate decreases. Varying the charge density of the deposited paint layer on the metallic substrate shows that a minimum charge density of deposited powder is required for the electric field enhancement phenomena to occur. The current modeling employs commercially available finite element software.