There are two types of paint used in manufacturing a product. They are wet paint which is solvent-borne or water-borne and powder coat which is fluidized solid.
Liquid paint can be applied using manual or automatic spray guns. In either case the spraying is done in a ventilated enclosure equipped to remove and filter out overspray paint. The amount of paint particles that may be discharged into the atmosphere is regulated by the EPA.
Both types of dip paintâ€”solvent and waterborneâ€”use the same type of dip tank. This tank has a paint-recirculation system to prevent settling of the paint material, and (if required) a paint-cooling system. The dip tank should be in a ventilated enclosure that prevents solvents from entering the surrounding area.
Flash-Off and Curing
After paint application and prior to curing, the solvents need to â€śflash-offâ€ť to prevent bubbling of solvent evaporating from the paint as higher temperatures are applied in the curing oven. Flash-off normally happens at ambient temperatures in an enclosed, ventilated area. The exhaust of this enclosure is discharged into the atmosphere (or to an air-pollution-control system).
All liquid paint application systems require these process steps:
- Paint application (spray or dip)
- Solvent/water flash-offÂ (evaporation)
- Paint curing
Electrostatic powder coating application requires two process steps:
- Powder application
- Powder melt/curing
Powder coatings can be applied manually or with an automatic system, using electrostatic spray guns.
Powder coatings are applied by electrostatically spraying charged powder so that it is attracted to the parts or by dipping heated parts into a fluidized powder bed so that powder melts onto the hot surface. Most coating systems use electrostatic spray. Powder coating is a very efficient way of applying a durable coating as long as large quantities of the same colors are being applied. If many colors and frequent color changes are required, this is time-consuming and therefore expensive. The decision to introduce powder coating to a facility involves many details concerning investment, labor costs and the variety of colors and parts.