When Powder Coating Is Needed

June 2013

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Save costs by doing it in-house

For fabricators that send out parts for powder coating, they might be better off offering this service in-house, as they would have better control over quality, work-in-process and lead times.

Systems to do powder coating are simple and the results can be a quality product with more profit for the business.

What is powder coating?

Powder is a dry coating that’s not dissolved or suspended in a liquid medium, such as solvent or water. It’s applied in a granular form directly to a surface. The powder is finer than ground pepper but coarser than powdered sugar.

Compared to paint, it provides a thicker and more durable finish. It’s a greener coating method that emits nearly zero compounds into the air and produces less hazardous waste, which makes the process more environmentally friendly than alternate liquid forms. It also offers a smoother part finish than paint.

It’s created by blending various components, such as binders, resins, pigments, fillers and additives, and processing them through an extruder into a continuous mass. This mass is cooled and broken into small chips, which are then ground into the powder. Each powder particle contains the components for reforming into the finished coating. Once the powder is sprayed on a part, mainly by using an electrostatic spray process, the part is sent through an oven where the powder melts on the surface and is then cured.

Powder formulation

Powder is offered in two types: a thermoset and a thermoplastic. When thermoset powders cure, there is the chemical crosslink, so that the coating will not re-melt. Examples of thermoset powders include epoxies, acrylics and most hybrids.

Thermoplastic powders do not crosslink when cured, but simply melt and flow over the surface of the part. The film hardens on cooling, but if reheated, it will re-melt. Examples of thermoplastic powders are vinyls, nylons and fluorocarbons.

How is the powder applied?

An electrical negative charge is applied to the dry powder particles, and then they are sprayed onto a neutrally grounded part. A part is typically grounded through the conveyor or hanger holding it. Through the electrostatic charge, the powder is attracted to the part and held onto the surface. A booth is used for the spray process to contain the over-sprayed powder and to collect the overspray and reclaim it for reuse.

To get more information on powder coating, Fab Shop Magazine Direct interviewed Joey Golliver, president of Powder X Coating Systems to see what it takes for a metal fabricator to offer this service.

FSMD: Often a fab shop will need to paint fabricated parts. They’ll send them out, because they don’t offer these services on premise. Does it make sense for a fab shop to be doing powder coating? And what would it take for them to offer it?

Golliver: Powder coating is a value-added process that they can bring in-house. The best thing is that it allows them to control quality and lead times and allows them to reduce or eliminate work in process.

Powder-coating businesses tend to be very profitable, and they usually have large back orders. We teach classes every month to people who want to offer this process, as they are outsourcing it. The reason they want to offer it is because of the three biggest complaints that we hear about: lead times, quality and the service cost.

In most cases, you would think that the price that they pay for the service is going to be the biggest driving factor, but normally it’s not, it’s the lead times. Then it’s quality and then being able to capture those dollars for the service and keep them in-house.

FSMD: With fab shops often processing parts that might fit in the palm of your hand to ones that are 6 ft. by 2 ft. long or even larger, what type of powder coating system would you recommend for a shop to get into?

Golliver: There really isn’t an off-the-shelf, typical solution for a powder-coating system. We have packages that try to cover most different part scenarios, but there is no way to cover them all. Therefore, we ask a lot of questions of the business before we specify a system for them.

My people are trained to listen first and then speak later. For us, it’s about being problem solvers. We have to ask the business personnel what they want to do with this system now, what they want to be doing with the system later and what they think their future needs will be.

We have to look at the quantities and different parts that they want to powder coat, because this can totally change the equipment that’s needed to do the process. It comes down to volume in conjunction with the largest part that the company is trying to do along with the specifications they are trying to meet.

FSMD: Describe a typical system that would handle small parts.

Golliver: There are two distinct levels of powder-coating businesses as defined by those of us in the industry who build equipment. It’s something that you’ll do as a hobbyist, or you’re doing it as a business to make money.

From a business standpoint, probably the smallest system that you’ll find is about a 4-ft.-wide-by-4-ft.-deep and 6-ft.-tall booth. This entire package with the gun, booth and oven would probably cost close to $20,000. If you look at it from a lease purchase, where you’ll find a leasing company to buy it and the business will make payments on it, the payments would be in the range of $500 to $700 a month. It wouldn’t take too many parts per month to pay for the system.

To be more specific though, a fabricating shop owner would have to determine the largest part that he would need to powder coat and the largest quantity of parts. Then he would need to determine the number of hours or how many shifts they would need to operate the system. He would need to look at cycle times for coating and baking the parts, along with racking the parts after the process. As you can see, there are a lot of different decisions that feed into purchasing a powder-coating system. But this is how we would help a fabricating shop make a decision on buying one.

FSMD: What about preparing the parts for powder coating? Is there anything special you have to do to clean them?

Golliver: The largest misconception in the powder coating business or any metal finishing business is in part preparation. We hear that parts just need to be sandblasted, or some other medium for blasting can be used, and then you powder coat them.

Let’s look at this logically. All metal is porous. If you have oil on the parts, which is often, and it’s sandblasted to clean it, where is the oil going after the process is done? Some of it is dislodged with the media, but a lot of it is going down into the pores of the metal.

The difference between powder coating and painting is that powder coating requires heat and a lot of it. If you push the oil into the metal, and it’s heated to 400 degrees, it’s going to come back out. This will destroy the finish of the part, and you’ll get a poor-quality powder coating.

For powder coating, there are times that the part needs to be mechanically treated. If it has weld splatter, slag, rust or anything on its surface, it will have to be mechanically removed. Once the surface problem is removed, the part needs to be chemically washed. Often this is done using a conversion coating chemical that is typically a phosphate.

This conversion coating serves three purposes: It’s for adhesion, appearance and corrosion protection. It etches the metal to make the powder stick to it. Without it, the coating would peel like wallpaper that doesn’t have enough glue behind it.

If there is oil or anything under the powder coating, heat will make a bubble in it and will leave imperfections in the finish.

Corrosion protection actually puts a very light coating between the surface of the metal and the powder itself. Almost every powder will not fail from the outside in, but because of oxidization underneath. That’s what the conversion coating chemical stops from happening.

FSMD: Why would powder coating be better than using wet paint?

Golliver: If you want to add this service as a value-added business, powder coating is far and away much better than liquid paint for several reasons. First, it requires much less skill to apply. It’s easier to train someone to powder coat than it is to paint.

Second, powder coating from an application standpoint is typically 30 to 40 percent less expensive to apply than paint, according to the Powder Coating Institute.

Third, it’s the cycle times. When powder coating is cured and cooled, it’s done. Painted parts can sometimes take hours or even days to fully cure before they can be handled.

Fourth, which is probably the biggest reason, is the environmental concern for the out-gassing of liquid paints. Wet paints have solvents. There are a lot of bad chemicals in paint.

The government is constantly squeezing in on painters who use wet paints. Powder coatings have no volatile organic compounds or solvents. The air inside the booth doesn’t exhaust back outside. It just takes out any powder that doesn’t stick to the part in the room.

Once you get past the initial cost of the equipment, you can’t beat it from a cost standpoint. Plus, I would say it’s a much more durable coating.

FSMD: What are the downsides of powder coating?

Golliver: If you were to look for a downside to powder coating, it’s the initial cost of the equipment. It’s more expensive than just using wet paint. Another problem would be that you can’t touch-up a powder-coated part without basically redoing it entirely. You can’t go into the field and spot spray a powder-coated part, whereas you can do this with liquid paints.

But on the flip side of this, while coating something for the first time with paint, if it gets messed up with sags, drips or things floating into the paint from the air, it has to set and dry before these problems can be taken out by sanding and redoing those areas. If the problems are really bad, then the entire part would need to be redone.

With powder coating, you won’t have any sags, drips or runs in the finish. If the part has a problem before it’s baked, it can be corrected. The powder can be blown off the entire part and sprayed over again.

FSMD: If powder coating gets scratched in the field, can you use a wet paint to fix it?

Golliver: Most of the larger, more established powder-coating companies do offer a pressurized-can paint that will match their powder colors. But this wet paint will never offer the corrosion capabilities of the powder.

FSMD: Does powder coating need a primer base?

Golliver: In most cases no, but if you want to, there are powder zinc-rich epoxy primers that can be sprayed on a part. Then a super durable polyester triglycidyl isocyanurate powder can be placed over the top of it for even better corrosion-fighting capabilities. But powder coatings rarely need a primer.

FSMD: How versatile are powder coatings?

Golliver: Anything can be done with powder coatings that can be done with wet paints. Clear coats, primers, candy and translucent powders are available. Powders are even available that give a chrome look, along with flat, glossy, glow-in-the-dark colors and ones that offer antimicrobial and antibacterial capabilities. Basically anything you want you can get.

Because it uses heat, the only thing that limits powder coating is the product that it’s applied to.

For more information, visit www.insidepowdercoating.com.

Powder X

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