Electrostatic deposition, commonly known as powder coating, is a dry, electrostatic process that uses pre-coated metal particles or powder.
It’s applied in a chamber with a series of electrodes and an electric current melting the powder as it comes in contact with the electrodes, fusing into the coated object. Once cooled, the final product has a thin layer of durable metal.
Here’s what you need to know about this protective coating and its benefits.
What is Powder Coating?
A powder coating comprises a polymer resin, combining pigments, curatives, flow modifiers, and other additives. All materials are initially melted-mixed, then cooled and ground into a fine powder-like flour.
Companies use powder coating for small parts, such as the handles of tools and equipment, and other items. It is available in various colors and finishes, and it’s often used as a substitute for painting and applied to many materials.
A Little History of Powder Coating
The method has been around for over 70 years. Writing at our sister site, here’s a brief history of where powder coating came from..
Introduced in the 1950s, powder coating is the youngest commonly used finishing process used and the fastest growing. Early applications required fluidized-bed applications with a typical thickness between 150 and 500 μm. The first uses of powder were functional rather than aesthetic.
Introducing electrostatic spraying opened the door for powder coating to become a commercially economical solution. Not only did this unfamiliar application process continue the practical use, but it also added decorative features. Spraying powder allows for thinner amounts of powder. It also increases the variety of components for coating, especially parts not previously coated through the wet application process.
Powder manufacturers developed epoxy, epoxy-polyester hybrids, polyurethane, and polyester resins in the 1960s and 1970s. This new technology became popular over traditional coating applications because of pollution and health concerns from organic solvents.
Commercial powder coating hit its sweet spot in the 1980s from improving color range, application efficiency, and textures. Powder coating, today, represents about 9% of all industrial coatings in the finishing industry.
How It’s Applied
After loading the components on a conveyor, they’re grounded with a negative charge while nozzles expel positively charged powder, resulting in complete coverage.
The next step is a trip through a curing oven system. Finishing companies use ovens with multiple stages, each operating at different temperatures.
Here’s a quick video illustrating the powder coating process.
Powder Advantages
There are several advantages to using powder coating versus other paint applications; the most common include:
Economical and Efficient
- It is less expensive to purchase powdered paint than wet paint because you can purchase the exact amount needed for a project.
- An electromagnetic charge ensures the powder sticks to the part, reducing waste.
- The powder is uncontaminated, undamaged, and recycled, then reclaimed for future applications.
- Powder coating saves time and money by eliminating unnecessary steps and lengthy drying times.
- Compared to wet coatings, powder coatings require less curing, processing, and drying. Liquid paint needs to dry at room temperature before curing; only then is the assembly possible.
Durability
Powder coating provides a long-lasting, economical, and durable finish by protecting surfaces against chipping, fading, scratching, and wear, all of which are common issues with other materials.
The finish is long-lasting, decorative, and protective—resistant to moisture, chemicals, mild impacts, and harsh weather.
Safety
There are also some safety concerns to keep in mind. Wet paint projects require more airflow and filtering to eliminate VOCs, while powder coating jobs require less airflow and air exchanges.
Both methods require exterior venting, but because powder coating doesn’t contain VOCs or solvents, facilities recycle the heated air, filter it, and return it to the shop.
This last statement may not sound too important, but winters in central Wisconsin get rather chilly, and we accept heat wherever possible!
Long-Term Maintenance
Powder coating makes long-term maintenance simpler. There’s no need to use any special solvents or cleaners; rinse with soapy water! Because of its corrosion resistance, dealing with damage or rust becomes simple.
Environmentally Impact
The powder is safe for disposal because it contains no solvents or harmful chemicals. During spraying, they limit waste because they emit no VOCs.
Powder coating also provides the following environmental advantages:
- Reduced carbon dioxide emissions
- No hazardous waste disposal
Quality
Wet paint issues, such as drips, runs, or unevenness, are present in a powder coating finish.
Disadvantages of Powder Coating
Everything has two sides. Here are some drawbacks to powder coating.
Limited Number of Substrates
Curing temperatures restrict the number of substrates available for powder coating: powder coating requires curing. The substrate must withstand curing temperatures without deformation to succeed.
Electrical current works only on specific materials, meaning nonmetal substrates for electrostatic spraying; therefore, metal finishers must use a fluidized bed powder coating process. Besides incurring additional operating costs, coating with a fluidized bed produces an inconsistent and uneven finish.
Thickness of Coating
It’s easier to apply thicker coatings than thin ones and produces better results. Thinner applications can’t hide imperfections found on the substrate. In these situations, wet coatings may be better options than powder coating.
Changing Lines
Changing color in a powder coating system takes time. Techs must perform a thorough cleaning job, ensuring the reclamation of unused powder. Missing powder increases the chance of cross-contamination, resulting in poor quality and finish.
Lengthy Curing Times
For most applications, powder coating requires less heating, processing, and drying time. The curing and drying times are longer for larger, heavier, thicker parts, which increase energy costs because it must sufficiently heat the material to ensure proper curing. A sufficient amount of heated air and exhaust is required to reach the correct temperatures, which also takes longer.
Spendy Start-Up
A proper powder coating application process requires:
- A spray booth
- Spray guns
- A curing oven
- The size and quality of the finished product limit the choice of curing oven
If a company can overcome these expenditures, powder coating quickly becomes a cost-effect process.
Conclusion
Powder coating is an excellent option for an item that requires a durable finish. The process uses a powder that is pre-coated and applied through an electrostatic deposition process that melts the powder onto the item being coated in a very thin layer composed of a thin layer of metal fused to the item. The process can take longer than paint but results in a durable finish with high corrosion resistance.
The upfront cost can be higher than paint, but it is worth it if you’re looking for a durable finish.