Powder charging back-ionization

Fig. 2 is a schematic representation of the electric field lines from the gun to a part that has a protrusion at its center. In this case, the electric field lines will concentrate at the protrusion. The charged powder and free ions will build up faster here and contribute to back-ionization. Because the powder particles are strong dielectrics, their charge will be retained for many hours, depending on a number of factors such as powder resistivity, as well as the ambient relative humidity. 

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