What is Powdercoating
Powder coating paint systems, also referred to as "dry painting", eliminate volatile organic compounds (VOCs),
hazardous air pollutants (HAPs), and solvents, and produce superior surface finish.
There are four basic powder coating processes: electrostatic spraying, fluidized bed, electrostatic fluidized bed,
and flame spray.
Electrostatic spraying is the most commonly used powder application method. For all application
methods, surface preparation (i.e., cleaning and conversion coating) is required to develop a good coating adhesion
substrate.
In electrostatic spraying, an electrical charge is applied to the dry powder particles while the component to be
painted is electrically grounded. The charged powder and grounded workpiece create an electrostatic field that pulls
the paint particles to the workpiece. The coating deposited on the workpiece retains its charge, which holds the
powder to the workpiece. The coated workpiece is placed in a curing oven, where the paint particles are melted onto
the surface and the charge is dissipated.
The choice of powders is dependent on the end-use application and desired properties. Typically, powders are
individually formulated to meet specific finishing needs. Nevertheless, powder coatings fall into two basic
categories: thermoplastic and thermosetting. The choice is application dependent. Generally, thermoplastic powders
are more suitable for thicker coatings, providing increased durability, while thermosetting powders are often used
when comparatively thin coatings are desired, such as decorative coatings. The principal resins used in
thermoplastic powders are polyethylene, polyvinyl, nylon, and fluoropolymer. Thermosetting powders use primarily
epoxy, polyester, and acrylic resins.
Powder coating virtually eliminates waste streams associated with conventional painting techniques. These waste
streams include air emissions, waste streams generated from air emission control equipment, and spent cleaning
solvents. Powder coating also greatly reduces employee exposure, and liabilities associated with liquid coating
(wet solvent) use. Because the powder is dry when sprayed, any overspray can be readily retrieved and recycled
regardless of the complexity of the system This results in shorter cleanup times. In all cases, the dry powder is
separated from the air stream by various vacuum and filtering methods and returned to a feed hopper for reuse.
Powder efficiency (powder particles reaching the intended surface) approaches 100 percent. Other advantages over
conventional spray painting include greater durability; improved corrosion resistance; and elimination of drips,
runs, and bubbles
