Advantages of Powder Coating Over Liquid Coating
In the previous article, I talked about pure cost per square foot savings and general material cost savings of powder coating over liquid coating. Today I’ll discuss some of the other advantage of powder coating that can save you significant time and money.
Curing Times Are Significantly Faster With Powder
The average catalyzed automotive or industrial liquid polyurethane is 2-4 hours cure to touch. The drying time can be accelerated by baking at around 235 F for 45 minutes, but that will only get the parts dry enough for limited handling. In most case, an extended cure time of about 1 hour is required before the parts can be assembled. Most liquid coated parts cannot be packed for shipment unless they have had an overnight dry time.
After the metal reaches a part temperature close to 400 F, powder coating cures on average in 10 minutes. Sometimes thick metal requires 30-45 minutes in the oven (and sometimes longer for especially dense objects). But after the part has cooled to handling temperature, it can be assembled and packed right away. Powder coating results in hours of saved process time and fewer parts in inventory waiting to be assembled or shipped.
Environmental Impact And Flammability Concerns Are Significantly Decreased With Powder
The average VOC (volatile organic content) of liquid coatings is between 3.5 to 5.5 pounds per gallon. This usually means about 1/3 to ½ of a gallon of paint goes into the atmosphere as emitted solvents. Many manufacturers have limits on how many tons (yes tons) of solvent they can put into the atmosphere. They have to pay for permits and will pay fines if they exceed their limit on these emissions. Powder has zero emitted solvents and no solvent flammability concerns. Using powder simplifies the permit process, reduces insurance risk, and generally provides a much more environmentally friendly process.
Processing Time And Number of Coats Are Greatly Reduced With Powder Coating
A regular polyester powder coating is comparable to a two component liquid polyurethane over an epoxy primer. Both systems need good clean metal that has had some kind of pretreatment to achieve maximum salt spray resistance. The liquid system then needs an additional primer to aid the topcoat in further durability and adhesion. Powder can eliminate the primer and be directly applied to the clean pretreated metal.
Powder also is 100% solids while liquid coatings average 50% solids. So if you have a paint thickness specification of 4 mils DFT(dry film thickness), then you can achieve this with one pass of powder. It will take 2-3 passes of the liquid coating, with some dry time in-between, to achieve the same thickness.
Powder Coating Is More Energy Efficient Than Liquid Coating
Powder coating equipment is generally much more energy efficient than equipment used for liquid paint. Because of safety concerns, liquid paint equipment uses more air and requires more air changes to filter out VOCs.
A liquid paint booth sized at 8’H x 10’W x 10’L uses approximately 16,000 cfm. A similarly sized powder spray booth uses approximately 8000 cfm, half what the liquid booth does. This means smaller fans and less shop air drawn through the booth when using powder. Liquid booths must also be exhausted to the outside to vent their emitted solvents. Since powder coating has no solvents, powder booths can be exhausted back into the shop by using HEPA filters on the final filter. The air is cleaner than the supply air that went into the booth.
If you are using a liquid coating oven to reduce your drying time, it will require more air exchanges than a powder coating oven. Since the powder oven can recycle its hot air more, it uses the burner less, thus saving energy.
Start Your Operation With Quality Equipment
Reliant Finishing Systems is a U.S. leading manufacturer of efficient and affordable powder coating equipment, from small batch systems for rims and wheels to large automated systems for constant throughput and rapid production. Whether you need to replace your existing coating equipment or are bringing a new operation in-house, our systems specialists can help. Give us a call today.
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