De-painting

Depainting is the removal of the paint film from various surfaces, primarily metals. Accomplishing this task typically requires the use of harsh chemicals, high-pressure spray, or media blasting. Other techniques, such as ultrasonically activated de-painting (UADP), are performed in a specialized bath. An environmentally friendly and flexible alternative is to use an atmospheric-pressure plasma jet (APPJ). To remove a thick layer of paint from the metal surface, a high-power plasma tool is required [1]. It can be achieved using a pulsed atmospheric plasma (PAA) jet, such as the PlasmaBrush PB3. Removing a macroscopic-thick film using the chemical action of the diffused plasma would take an unacceptably long time. This task can be accomplished physically. When applying the pulsed transferred arc to the paint layer, a large portion of the power can be deposited within the paint, causing micro-explosions. They occur as a series of hot spots, as described in the study by Beilis [2].

The prerequisite for such a physical mechanism is a high dielectric loss coefficient, which allows the deposition of high-density power within the paint film. Such a mechanism explains why this technique is unsuccessful at removing high-purity oxides, which typically exhibit low dielectric losses. Also, the film’s high thermal conductivity can hinder reaching the high temperature required for the micro-explosion. It was shown that, despite high power densities, micro-discharges have no detrimental impact on the substrate material [3].

Figure 1. Aluminum sheet painted with yellow primer and white topcoat, depainted by PlasmaBrush PB3.

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