Monthly Archives: June 2015

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

Powder coating can help you get the results you want in a fraction of the time.

Powder coating can help you get the results you want in a fraction of the time.

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.

If you are looking for more educational information, please check out our Resources page.

 

Switching From Liquid Paint To Powder Coating: What You Need To Know

Powder coating is a more economical and longer lasting alternative to traditional wet paint application with far less environmental impact. If you’re comparing these two finishes from a production standpoint, here’s what you need to know.

Powder Coating Is More Durable Than Liquid Paint

Powder Coated Pipes

Powder coated items are more durable and last much longer compared to liquid paint.

Switching from liquid coating to powder coating has many advantages. From a performance perspective, powder coating is more durable physically and chemically. Most liquid coatings are typically softer than an average powder coating. When coating parts like semi-truck wheel rims, this improved durability and corrosion resistance make trucks safer and longer-lasting. In the oil fields, replacing corroded pipes or junctures is expensive and leads to oil flow downtime. These parts and fixtures are perfectly suited to powder coating and benefit from its performance advantages.

Powder Coating Is More Efficient & Easier To Use

If you’ve worked with liquid paint, you know that mistakes can be time-consuming and costly. In comparison, powder coating is generally much easier to apply. Operators require less training to apply a quality finish and mistakes can be easily fixed with powder (as long as you catch them prior to curing). Since rework issues are fewer and coating is usually faster, you can coat more items on a given day. You can expect increased throughput with fewer errors by switching to powder coating.

Most Importantly, Powder Coating Is Cheaper  

Cost savings are another great benefit to powder coating and often provide a very fast return on investment.

Since everyone has different size and shaped parts they need coated, we can determine ROI by calculating a 1 square foot panel cost. For this example, we’ll eliminate the labor and fixed costs and focus on just material costs. This will show the cost savings of powder coating versus liquid coating.

For our examples, I’m going to compare the amount of powder versus the amount of liquid paint to cover a 1’ square at a standard 2.5 mils. The mil, or thousandth of an inch .001, is most commonly used in engineering or manufacturing. It is used to specify the thickness of items such as paper, film, foil, wires, paint coatings, latex gloves, plastic sheeting, and fiber. (For example, most plastic ID Cards are about 30 mils in thickness.)

I’ll be calculating material costs using the coverage formula:

192.3 / Specific Gravity / Film Thickness = Coverage (Square feet per pound)

Let’s use a 1.4 specific gravity powder at 2.5 mils. The powder costs $4 a pound and we calculate our transfer efficiency at 70%. 192.3/1.4/2.5 = 55.2 coverage at 100% TE. 55.2 * 0.7 = 38.64. $4/38.64 = $0.10.

It costs $0.10 for a powder coated 1 square foot panel at 2.5 mils.  (For more info, Akzo Nobel has a great online calculator to do this at: http://www.interpon.us/our-coatings/powder-coverage-calculator/)

To get the same 2.5 mils DFT in a traditional liquid polyurethane, it will take a different calculation. Coverage is:

 ft2/U.S. Gallon = (%Solids/100 *1604)/ DFT (For a more comprehensive description of the liquid paint coverage formula: http://www.wellservicingmagazine.com/featured-articles/2007/11/applied-cost-a-useful-tool-in-paint-purchases/)

So to get 2.5 mils DFT with 45% solids polyurethane, 1 gallon can cover 289 square feet at 100% transfer efficiency. The average price for catalyzed polyurethane is $55, so at 50% transfer efficiency we get:289/2= 144 ft2 coverage and $55/144 = $0.38 paint cost per square foot. 

It costs $0.38 for a liquid coated 1 square foot panel at 2.5 mils.

Note these are only material costs. Liquid coating usually takes multiple passes and has much longer dry time. Flammability and waste disposal are also a concern for liquid coating operations.

In this example, the powder costs 3 times less. If a liquid coating operation uses $100,000 a year on paint costs, they can cut their paint expenditure by $50-60,000 being conservative. That difference is the price of a nice medium sized powder coating batch system.

Can I Use Liquid Paint Booths For Powder Application?

Powder coating equipment reliant finishing systemsWhile it is certainly possible it is definitely not recommended. Liquid booths are geared for a larger airflow pull than their powder equivalents. Too much airflow and you start pulling powder away from the part. This wastes money. Also, if you plan on continuing your liquid operation, you do not want to use powder and liquid in the same booth. It plugs up your filters fast and is a safety hazard if you are using solvent based liquid paint.

In future articles, I’ll be explaining more of the differences between liquid paint and powder coating, including specifics on transfer efficiency, waste, and energy savings. If you have any questions at all, or any topics you’d like me to cover, please e-mail me at bruce@reliantfinishingsystems.com

Looking for more information on powder, powder coating and application techniques? Please visit our growing list of articles on our Resources page.