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Powder coating

Applications

In contrast to wet painting, which also functions without electrostatics, powder coating requires electrostatics. The powder particles stick to the workpiece through image charging. Powder particles, which have no charge, do not stick to the workpiece and fall down. Basically there are two methods of charging:
By ionization (Corona powder coating)
By friction (Tribo powder coating)

Corona-Powder-Coating

Bei der Corona-Pulverbeschichtung wird meist ein Miniatur-HS-Erzeuger (Kaskade) verwendet, welcher in der Sprühpistole eingebaut ist. Die Leistungsklasse dieser "Kaskaden" liegt in der Regel im Bereich 80-90 kV und max. 100 µA. Eine Nadelelektrode am Auslass der Sprühpistole erzeugt einen mächtigen Ionenüberschuss. Dies führt zur Ladung der Pulverteilchen. Die Pulverteilchen werden vom geerdeten Werkstück angezogen und haften durch ihre Spiegelladung. Da Pulverteilchen nichtleitend sind können diese ihre Ladung nicht an das Werkstück abgeben und haften dadurch bis zum Verschmelzen im Ofen.

Corona-Powder-Coating

Tribo powder coating

Tribo powder coating functions without high-voltage generation. The powder particles are charged through friction. The powder-air mixture is guided in a swirl through a long plastic tube. A strong charge-generating plastic, such as PTFE, is used. So that this also does not become continually saturated and thus can no longer generate a charge, it is covered with a grounded metal sleeve, for example. The Tribo current can be measured in the ground conductor of this metal sleeve. The charged powder particles are pulled in by the grounded workpiece and stick due to their image charge. Since powder particles are non-conductive, they cannot give off their charge to the workpiece and stick until melting in the furnace.

Tribo powder coating