Electrostatic powder coating is one of two varieties of powder coating and requires the use of devices that produce the effect of charging paint particles. The powder paint has a granulation in the range of about 10 µm to about 100 µm. Paint feeding is supported by compressed air, which is additionally used to fluidize the powder. Polyester, epoxy, polyurethane, silicone and epoxy polyester paints are commonly used.
Painting with powder paints involves applying powder paint to a metal coating by electrostatic spraying. When an electrostatic field is created, the painted surface attracts its particles, so the paint particles are negatively charged during spraying, while the surface particles are positively charged. Such a process is possible due to the fact that a constant voltage and current flows through the whole system. As a result of this action, paint particles are attracted to the surface and adhere evenly to it, even for small-sized items. In this case, painting is relatively simple, since it is not required to rotate the object. For elements of larger dimensions, spraying from all sides is necessary, because one-sided is not enough to cover the entire surface accurately.
There are two methods for electrostatic charging of powder paint:
• Crown method - high voltage and spray gun with electrode are used. As current passes through the gun, an electrostatic field is created between the grounded, painted component and the electrode. This method allows paint particles to settle on the surface.
• Friction method - the paint is loaded as a result of friction of paint particles against the gun walls. Not all powder paints can be used with this method, such as metallic powder paints, which do not have the necessary dielectric properties.
Electrostatic powder coating is associated with the Faraday effect. Paint particles are attracted to the surface that is closest to each other, making it difficult to cover paint surfaces with complex shapes. Due to electrostatic painting it is difficult to cover e.g. the inner part of a given element. If you would like to learn more about powder coating at JARD Creative, write to us at email@example.com