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Powder Coating Outdoor Equipment Can Improve Your Business

Powder Coating Outdoor Equipment Can Improve Your Business #reliantfinishingsystems

Powder coat playground equipment to make it durable

Outdoor equipment is one of the largest and fastest growing markets for powder coating.  This is no surprise, since powder coating outdoor equipment makes good sense for both equipment builders and their customers.  From playground equipment to sporting goods, powder coated outdoor products last longer and perform better. In this article, we’re going to look at how powder coating systems reduce costs and produce a better outdoor product.

Powder Coating Versus Wet Paint

Almost all metal products that are going outside need to be finished in one way or another. Preventing rust is one of the main reasons that metal coatings were invented. Properly prepared, a finished metal object will outlast an unpainted one. So, why is a powder coating system better than wet paint methods for outdoor equipment? The simple answer is that powder coating is cheaper to apply and typically lasts longer.

Powder Coating Is Cheaper To Apply

Just one powder coating application is as strong as many coats of wet paint #reliantfinishingsystems

Just one powder coating application is as strong as many coats of wet paint

A single coat of powder is just as scratch-resistant and durable as a multi-stage wet paint application. Yes, automotive paints can last as long, but those types of wet polyurethane are coatings are expensive and require more steps.  First, you have to properly prepare the metal, then prime it, then apply a two-component color coat, and finally apply a clear topcoat. The material cost alone is usually four times that of powder – to get a similar result.

 

Graph showing 75% relative savings on material costs in powder coating system versus wet paint

Powder coating raw materials for metal parts costs 25% of wet paint methods

Not only are raw materials cheaper using a powder coating system, but there’s less handling and preparation of the parts! Powder coating is much easier to apply than wet paint. Since powder is simpler to apply, painters will produce fewer flaws, such as sags and runs.  They will also need less practice. The average cure time for a metal part is about 20 minutes to bake and 10-15 minutes to cool, so you can typically handle, assemble and pack your parts much faster than when using a wet paint method.

Outdoor Powder Coating Lasts Longer

Furniture with Powder Coating Outdoors

Powder coated outdoor furniture will last much longer and continue to look nice

What about durability benefits in powder coating outdoor equipment? Since rust is usually our primary concern, what kind of resistance to corrosion does powder coating provide and for how long?

 

Checking For Durability With Salt Spray Testing

Examples of Salt Spray Testing

Examples of salt spray testing

Perhaps we want to determine how resistant a coating is to corrosion.  We can use a common industry test called Salt Spray Testing.  This simulates extreme outdoor conditions by spraying a coated part with pressurized air and saltwater.  The salt spray test is used to determine how long a finish might last before rust and corrosion compromise its integrity.

Salt Spray Testing Method

  1. Start with a coated sample part.
  2. Scratch the coating all the way through to the metal in an X pattern.
  3. Blast the part in a testing chamber with 5% or higher salt spray solution.
  4. Time how long you’re spraying.
  5. When rust has reached 1/4″ or more from the scribed point, stop spraying. How much time has elapsed?
  6. Compare this time to other coatings’ times.
Salt Spray Testing results on three coating methods
Process Avg Salt Spray Hours
1) Grinder, solvent wipe, liquid enamel 50
2) Grinder, solvent wipe, powder coat 250
3) Blast, pressure wash, phosphate, powder coat 1000

Here’s some results from different coating processes. The powder coated sample –
with no other preparation or special treatment – lasts on average five times longer than the same object finished with a common wet paint.

Salt spray testing is a controllable lab test that simulates tough conditions to determine overall finish performance when powder coating outdoor equipment. However, many variables will affect true performance.  This test gives only a rough estimate of how resilient any finish is. If you use powder coated equipment on the Florida coast, 100 hours could equal one month.  But if you are in Arizona 100 hours could equal 15 years. Climate, local weather patterns and equipment usage all play a part in how long your finish will last, but the more salt spray hours your part takes to rust, the better.

Customer Example: Swapping To Powder Coating Can Help Your Outdoor Product Business

Joe’s Trailers is a sample business that wants to provide its customers with durable products. Joe’s Trailers can show how a typical small manufacturing business can easily change its methods to get better results from powder coating outdoor equipment.

 

 

Joe’s Trailers started with this wet paint process (Process 1 from the Test Results above)

  1. Grind the welds down and the mill scale off the metal
  2. Wipe the trailer down with acetone
  3. Spray an industrial enamel wet paint

When Joe tested a panel that was coated using this wet paint process, it got these results:

The panel took 50 hours to get 1/4″ creep of rust on the scribed mark

But, Joe sometimes needs to store the trailers outside for a long time.  He also sells them in areas where road salts are used.  The wet paint finish on the trailers isn’t lasting, and customers complain.

Joe responds to customers’ concerns

Outdoor Powder Coating On Trailers

Powder coating can help heavy wear products – like trailers – withstand day-to-day use and extreme conditions

Joe decided to purchase a powder coating system to increase quality and reduce material costs. He kept the same preparation. But with his new powder coating oven, he got 250 hours of salt spray before there was a ¼ inch of rust creep with the powder coated finish (Process 2 from Test Results above).  This was five times longer than with his wet paint technique. That’s a level of protection so thorough that no trailers rusted in his storage lot while they were stored outside during the off-season.

Joe expands his business to a new kind of customer, increasing profits

Joe got a call from an upscale landscaping company located near Chicago. This customer wanted his trailers to last longer than the current trailers he bought from a local home improvement store. The customer couldn’t use ugly, rusted trailers in his service area because of his demanding clients, and the winter road salt quickly corroded his trailer fleet.

Joe decided to make some improvements to his powder coating system.  He already had a powder coating spray booth and powder coating oven.  He decided he could improve his pretreatment.  Joe invested in a blast booth, and a special pressure washer that generates steam.

Now his process is

  1. Blast the welds and scale, which is quicker than grinding
  2. Apply cleaner, rinse with water, steam with phosphate, and rinse
  3. Coat with powder in a powder coating spray booth
  4. Bake powdered parts in a powder coating oven

This new piece lasted 1000 hours in the salt spray testing chamber before the rust creep reached 1/4 inch (Process 3 from Test Results above).  Because the finish was so durable, Joe was able to offer a four-year rust warranty.  He increased his prices to cover labor and equipment.  He even got more profit from these upgraded trailers than his basic trailers.

Consider powder coating systems for outdoors products

Switching to a powder coating system can greatly increase coating performance and durability.
Consider it especially for products that must suffer the wear and tear of outdoor use. Products will last longer in outdoor conditions. Business costs like product storage damage, customer returns, and premature warranty issues will be reduced. Finally, higher prices can be charged for better products.

Agriculture Equipment with Powder Coating Outdoors

Powder coating can provide performance and cost benefits across a number of markets

This example has focused on trailers. Remember that these benefits apply to any outdoor product, here’s some ideas to get your creative ideas flowing:

  • Handrails, fences, and playground equipment.
  • Automotive parts like truck accessories, and farming machinery
  • Seasonal items like fishing and marine equipment, deer stands, and much, much more.

When taking on a new powder coating project, remember to ask your customer what they need. Get the correct coating procedure in place to meet their expectations. Use your vendors as resources to help you tailor your powder coating equipment, powder, and pretreatment methods to exceed your customers’ needs.

Reliant Finishing Systems provides fully integrated powder coating equipment. Whether you want to supplement your existing system, or install a complete finishing line, feel free to call us today about any of the following:

What Coaters Need To Know About Powder Coating Particle Size

Powder Coating Particle Size

When troubleshooting your powder coating, you may find specific issues caused by the powder coating particle size.  Unfortunately, while a lot of information is available on this subject, most of it is very technical in nature and doesn’t explain the real-world production issues that are caused by improper powder coating particle dispersion. If you’re looking for practical knowledge to improve your results, these basic guidelines will help you identify finish problems related to particle size.

How Powder Manufacturing Creates Different Particle Sizes

When powder is manufactured, it is combined in a giant mixer, melted, cooled into a big sheet, and then broken up into pieces. It is then ground and sifted through a screen to the specific particle size the powder manufacturer has designated.

During the manufacturing process, there are three types of particles produced: standard, fine and large.

Standard Particle: This particle size is what the manufacturer wants to put in the box. The size range of the particle is very tightly controlled, Standard particles will produce the best possible finish and generate proven, heavily tested results.

Fine Particle: This particle is very small and could cause some finishing issues like picture-framing if there was too much allowed to be packaged. The fine powder particles build up at a different rate from the standard particles, especially in areas of “wrap”, and cause unacceptable variations in the finish.

An excessive amount of fine particles can also contribute to application guns spitting or sputtering because fine particles can be fluidized more easily than standard particles. During the grinding process, powder manufacturers have suction hoses above the grinders to catch a lot of these fine particles that would not otherwise be sifted out. Fine particles, by nature, float in the air more than standard particles. That’s why the suction hoses can catch most them.

For more information, visit this powder troubleshooting guide from Tiger Drylac. Specifically, on page 16 of the document, they show a good example of “picture framing” due to excessive build-up of fine powder. http://www.tiger-coatings.com/fileadmin/user_upload/downloads_us_new/technical-information-sheet/tiger-drylac/TIGER_Drylac_Troubleshooting_Guide.pdf

Large Particles: This particle is too big to pass through the final filter screen. Sometimes manufacturers will re-grind these large particles to get good powder out of them, but sometimes they just throw them away. If large particles wind up in a box of powder because of a manufacturing error or flaws in the screening equipment, they do not hold a charge as well as a standard particle and will most likely wind up on the floor of a spray booth. In addition to decreasing your transfer efficiency, an excessive number of large particles can cause the part surface to be more susceptible to powder loss during pre-cure handling, resulting in thin spots that can’t otherwise be explained. (to learn about Transfer Efficiency, read more here.)

Some fine particles and some large particles will wind up in the powder box regardless of the process being used. The powder coating manufacturer has a particle size distribution analysis machine to measure samples of powder and see how much variation the powder particles have. In a normal box of powder, there shouldn’t be enough large or fine particles to cause problems. 

Typical distribution of powder coating particle size in different powders.

What Is The Powder Coating Particle Size Supposed To Be?

There is no standard answer, because each different type of powder has specific particle size requirements due to the special effects components or pigment used in its formulation. Regardless of size, the key to good powder is generally to have as tight a particle size spread as possible.

Typically, smaller particles carry better charge and fill voids in the coated surface better, but they do not penetrate Faraday Cage areas well. To get a powder that both holds a charge well and creates an even distribution, the manufacturer will usually decide on a happy medium for the average particle size based on laboratory and sample production testing.

Here is an example of a graph of a sample of powder:

Powder Coating Particle Graph

As you can see, there is a curve to the distribution. That means that some particles are a little bigger and some are a little smaller. The more peaked the curve is, the more reliable your finish should be. If the curve is flattened and you have a lot of fine particles or large particles, you could have more finishing problems and/or worse transfer efficiency.

Powder Coating Issues Related To Powder Particle Size

Powder coating particle size discrepancies can create issues with the quality of your finish and can increase your applied cost. These problems can be especially troublesome in a production environment, especially if you use a reclaim system as opposed to spray-to-waste. If you don’t reclaim and reuse spent powder, the particle size in the box is all you have to worry about. If you reclaim your powder, then you need to consider powder particle size even more closely. It’s likely you will have some adjustments to make to achieve your best finish.

“Virgin” powder, straight out of the box, will typically be more conductive than reclaimed powder. The reason for this is that there are some large particles, as well as some inert particles that were part of the original powder formulation. These particles are most likely to fall off the part and get recycled back into the powder supply. As you use more reclaimed powder, this percentage grows and your powder does not adhere as well to the parts. Most powder experts recommend a ratio of at least 60% virgin powder to 40% or less reclaimed powder to get acceptable finish results.

Remember, the fine particles will usually adhere to the part or get stuck in the exhaust filters of the booth, so it’s mostly the heavy particles (that are the least attractive to the parts) that get recycled. Some particles, even those of ideal size, will stick together due to contamination or partial gelling in hot environments. These clumps of small and standard particles act like large particles and don’t stick to the parts during spraying. It is important to hand filter all of your reclaimed powder or use an automatic sieve to filter reclaimed powder being pumped back into your powder hopper.

What If I Think I Have A Powder Problem?

Powder Coating And Color Chart

If you think you may be having a finish issue that’s linked to a problem with your powder, always start by contacting your powder supplier. Powder coating vendors have access to tools that the average powder coating shop or finish line manager does not. Listen to your powder supplier and follow their suggestions. Don’t be shy about asking them to look into potential powder problems, but remember that most coating defects are due to process issues, not defective powder coating media.

In a spray-to-waste environment, your supplier may elect to replace questionable powder or have it analyzed to confirm that it isn’t defective. It’s likely that they will want to review the way your using their product, and they may find a production issue that you’ve overlooked.

If you do a lot of reclaim, your powder supplier can test your virgin and reclaim samples to let you know what you can expect from your powder as far as average powder particle size. By keeping good ratios of virgin and reclaim, you can adjust your guns to the appropriate settings to get repeatable, high-quality finishes.

Need Expert Help?

Reliant Finishing Systems is a U.S. manufacturer of high-performance powder coating equipment. In addition to building powder spray booths and powder curing ovens, we manufacture blast rooms and wash stations. We also have experienced powder coating specialists on-staff and offer line audits and on-site troubleshooting. If you need powder coating equipment or expert advice, give us a call today.

An Introduction To Powder Coating Quality Control Testing

Once you’ve completed a powder coating job, your next step is quality control testing. Whether the coating has to withstand harsh environments or resist normal wear and tear, you – and your customers – need to know what to expect from your coating work.

Profitable job shops make sure they meet their customers’ coating specifications. Successful manufacturers also perform rigorous testing to ensure that their powder coated products meet pre-set standards. If you want to retain customers and expand your powder coating business, you need to focus on the quality of your work. The same attention to quality is critical if you want to keep an in-house coating department on the right track.

Flexibility, color, gloss, adhesion, corrosion resistance, chemical resistance, durability, film thickness, proper curing and overall appearance are all things you can test for as part of a quality assurance program.

Practical Quality Control Testing Methods

No matter what you are coating, there are a few tests you need to add to your daily process. The most common areas to test for basic powder coating functionality are:

  • Film Thickness
  • Uniformity/Proper Curing
  • Adhesion
  • Appearance

Because proper quality control testing is so important to your success and reputation, we recommend these tests be performed daily, or at least once with every batch of products–and any time you change your coating products or processes.

 Powder Coating Film Thickness Testing

powder-coating-gauge-for-quality-control-testingA film thickness test determines the thickness of the powder on the part once it’s been cured. This is generally confirmed with a Dry Film Thickness gauge. These gauges are fairly affordable and easy to use.

A common range to look for is 2-3 dry mils (thousandths of an inch). A coating of 2-3 mils usually provides complete coverage of the powder over the metal.

Remember: Make sure that if you powder coat both steel and aluminum, you purchase a gauge that will measure both ferrous and non-ferrous metals.

If you are getting less than 2 mils, you are at risk of not providing full coverage on the product. If you are over 5-7 mils in a single coat, you could be wasting powder or causing surface appearance defects like “orange peel” or runs. In either case, adjustment of the powder coating application is needed.

Powder Coating Uniformity/Cure Testing

mek-solution-for-powder-coating-testingWhen we talk about “cure” in quality control, we’re talking about the correct temperature and dwell time that allows the powder to achieve it’s formulated hardness and chemical resistance properties. When testing for cure, you want to make sure that there aren’t any areas of overbake (where the powder has cured in a dry and brittle fashion) or underbake (where the powder has not completely cured).

A cure test is easy to perform. Proper curing is confirmed by rubbing a methyl ethyl ketone-soaked cotton swab lightly over a cured panel or part (in an inconspicuous area if the part is to be used if acceptable). Application of 20 double rubs (back and forth over the same spot) is a common standard for checking cure, but you will usually see failure after about only three or four passes. If the finish deteriorates to the point that you expose bare metal, your cure is lacking or the powder is defective. If the coating softens but then recovers, you are fine. Some color may transfer to the cotton swab, but that is normal, especially with hybrid powder coatings.

If your parts are failing their cure tests, temperature in the oven or dwell time in the oven may need to be increased. Be careful when adjusting your process not to overcure, as that can cause issues like adhesion failure; dulling of gloss; or yellowing and browning of the color, especially if you are coating white.

Powder Coating Adhesion Testing

Adhesion testing measures how well the powder sticks to the part once it is fully cured. As with the cure test, your adhesion test results can be affected by overbake or underbake.Generally, adhesion testing kits are available for specific testing requirements.

You can perform a simple adhesion test on your powder coated products using some common tools you likely already have at your shop – but remember, the adhesion test is a destructive test. Do not do this on parts you want to use because this test will ruin the finish.

Adhesion Testing Supplies For Powder Coating Quality Control TestingTo perform the adhesion test, you will need some sticky clear tape and a utility knife. You will also want at least one test panel that you have already coated and cured.Make sure the part or test panel is clean and dry.

Again, this is a destructive test, so make sure you test adhesion on a part you won’t mind throwing away or completely reworking.

 

Next, using the utility knife, scribe a section of the part five times one way and then again 5 times perpendicular to the first scratches.This will give your part’s coating a grid-like appearance. Make sure you cut through the coating to the metal.

powder coating grid for adhesion testing

After making the cuts, put a piece of tape over the grid and smooth out any air bubbles. The tape should completely cover the grid. Pull the tape off aggressively and look at the tape and the part. An acceptable result will show only a little of the powder coming off from the grid cuts. If a square or two of coating is removed, adhesion can be suspect. If your coating comes off in a sheet, then you have adhesion failure.

Adhesion failures can be caused by several factors. One of the first places to look is metal preparation. If the metal is too slick or oily, powder will not be able to stick to the surface. Make sure the substrate is clean and etched/abraded. Overcure can also cause the powder to become so brittle that it will easily pull away from the metal. Old powder may have issues that can cause lack of adhesion as well. Proper process evaluation will lead you to the cause of the failure.

Powder Coating Appearance Evaluation

Powder Coated Parts On RackOne of the advantages of powder coating is how good the finished product looks. All your products should be inspected before shipment to make sure that there aren’t gaps in coverage, bubbles, warping or poor coating application. If your quality assurance manager is actively looking for defects, problems with the powder or the product can be fixed before delivery.

 

The second part of your appearance testing routine involves taking time to communicate with your customers. Every customer should have an idea of what he or she considers to be an acceptable finish, but it may take some discussion to determine what’s realistic and measurable. A finish standard can be as simple as no more than two visible surface imperfections per square foot. Or it can be no blisters or pinholes visible on the primary surfaces. Gloss and color standards may also be included. If a customer has very precise requirements, we recommend investing in a gloss meter/color eye (spectrophotometer or similar) to make certain the customer receives exactly what they expect.

Appearance issues can be caused by many factors. Contamination is usually the biggest problem. Shop dirt, welding debris, sanding dust or other airborne contaminants can get on the parts. These substances can cause the powder to react negatively or simply fail to cover the contamination. Proper cleaning and pretreatment can address these issues.

Unfortunately, improper cleaning contributes to many appearance issues. Ignoring rust or residue can prove costly in the long run. The use of poorly mixed or overly-diluted chemicals, the application of inappropriate detergents, and other pretreatment shortcomings related to carelessness can also cause significant finish problems.

Sometimes water in compressed air lines or high humidity in the shop environment can cause powder to clump and generate unwanted appearance issues. Evaluating your process by eliminating one variable at a time is crucial for discovering what’s causing the issue.

Adding Quality Control To Your Powder Coating OperationInspecting Powder Coating For Quality Control

Generally speaking, the four basic tests discussed in this article should be included in any powder finishing process. Other periodic laboratory tests may be needed. These include salt-spray, UV exposure, QUV, taber abrasion testing, etc. Most of the lab testing can be done by your powder supplier. Be sure to communicate fully with your customer, as well as your powder media and pretreatment chemistry suppliers, to clarify what testing is required and what standards the finished parts must meet.

Need Help Getting Your Line Back Into Shape?

Reliant Finishing Systems manufactures all types of powder coating equipment and offers a wide variety of repair and troubleshooting services for the powder coating industry.

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Need equipment? Reliant builds blasting enclosures, gas and electric ovens for parts drying and powder curing, environmental rooms, powder application booths, spray walls, multi-stage parts washers, and manual wash stations. Our systems specialists have years of experience with the design and installation of powder coating lines of all sizes.pic-4-1

If you already have equipment in place, Reliant can help. Whether you need a line audit to help you increase throughput or simply need to run a Datapaq to diagnose possible hot spots in your oven, our team of experienced technicians can help. Give us a call today.

Using Masking and Plugs for Powder Coating

espos powder coating masking example

Thanks to Espo’s Powder Coating for providing a great example of proper masking with this turbocharger housing.

Regardless of what you’re powder coating, there will likely be an area on your part where you DO NOT want any powder coating to be applied. Screw holes, pipe fittings, precisely machined surfaces and sleeves or cylinder interiors are some of the places where powder will interfere with the fitment needed during assembly. If powder gets in the wrong place, it can definitely cause problems down the line.

Thankfully, there are a couple easy techniques you can use to prevent powder from going where you don’t want. By using “masking” and “plugs,” you can get the results you need. This article explains when to use masking and plugs for powder coating and also describes the supplies you’ll need in order to use either method. Follow these simple tips and you’ll soon be producing incredible-looking finishes that fit together perfectly during assembly.

Masking For Powder Coating

Powder Coating Masking TapesMasking is the term we use when we want to shield fairly large areas of a part during the powder coating process. For powder coating masking, a high-temperature masking tape is required. Some companies use the term “high-temperature masking film,” especially for larger tape sizes or material that can be cut into sheets.

Remember: Powder curing typically takes place between 380° F and 450° F, so be sure that your masking material is rated for those temperatures before using.

Masking is usually done after the chemical pretreatment stage of your coating process. Follow your pretreatment steps as normal and allow the part to dry fully before applying the high-temp tape to any areas that require masking. The pretreatment process will provide the uncoated metal with some amount of corrosion protection prior to assembly.

If the metal requires blasting prior to coating and needs to be masked before blasting, you will need a different, more durable tape. Resilient high-temp tapes can be left in place, but they are usually fairly expensive. Alternatively, you can also use a thicker version of normal masking tape. You would apply it for the blasting process, remove it after the part has been blasted, and then apply high-temp tape over the areas you want to shield. If you use chemical pretreatment after blasting a part, be sure all tape is removed before the part is treated. Mask the part with high-temperature tape only after it has dried fully and you’re ready to coat.

When working with high-temp masking tape, the tape stays in place while the part is being sprayed and cured. You should be able to coat and cure the part as usual after the tape has been applied. Once the part is fully cured, you remove the tape.

TIP: When removing the tape, try to take it off while the part is still fairly hot. Around 200° F is the optimal temperature to remove the tape. If you take it off too early, while the part is too hot, it can cause strings of powder to pull off at the edge of the tape and result in a defective finish. If you wait until the part is too cool, there can be chipping or a rough line along the edge of the coating when the tape is removed.

Advanced Masking Technique: Two-Tone Powder Coating Finishes

advanced powder coating masking techniquesTwo-tone and multi-color finishes are achieved when two or more different colors of powder are applied to the same part. High-temperature tape and/or masking film is used to achieve this type of finish. A two-tone finish is applied like any other powder coating that requires masking, but special care should be taken to ensure that the results are acceptable.

When applying two-tone or multi-color finishes, you may need to use slightly different masking, coating and curing techniques than you normally would. You’re still dealing with a situation where you’ll be spraying a part and some portion of the part shouldn’t have any powder applied to it, but you will need to spray and cure the part more than just once.

Recommended Rules For Two Tone Application

When masking the part, always try to limit skin contact on the bare metal. Your skin has oils that can cause issues later when you apply the remaining color(s).

As with normal masking, take the tape off of the part when it is around 200° F. A handheld laser-pointer IR temperature gauge is good enough for checking the metal temperature after curing, once the part is outside of the oven.

Make sure the first coat is fully cured and cooled before re-taping for the second color. The adhesive on the tape can cause finish problems if the powder has not fully cured. Also, you may want to wipe the remaining bare metal surface with alcohol before coating just to make sure no contaminants are still on the surface from the previous masking. For multi-color finishes, you’ll re-mask the part after each coat has been applied and cured.

Check with your powder provider in advance to be sure that the powder you’ll be working with is appropriate for two-tone or multi-color applications. You’ll also want to consider just how long to cure the part each time you spray a new section. You may need to adjust the curing temperature to assure that each coat is adequately cured without becoming discolored. It is easy to under-cure the last coat if you become concerned about over-curing previously applied powder. Remember that most powders are hard to over-bake if you are careful.

Two-tone finishes require extra care to get right, especially if the line between one color and the other is on a flat or oddly contoured surface. Extra care when masking can make the difference between a great finished product and a reject, so take your time.

Plugs For Powder Coating

powder coating plugsPlugs are commonly used to keep powder out of screw holes or other recesses where powder would interfere with the assembly of a part or its working operation.

Remember: Just like masking, make sure your high-temperature plugs are rated for the appropriate oven temperature. Always check the temperature rating on the plug before using.

Like tape, plugs are also used after pretreatment. Prior to inserting the plugs, blow out the holes with compressed air to ensure all moisture is out of the part. Trapped moisture in hard-to-reach areas can cause surface defects if the moisture leaks from the part during the curing cycle.

Plugs can be reused, as long as they do not get impregnated with powder. When reusing plugs, try to remove as much old powder as possible from the plug to keep from contaminating the next part.

TIP: When removing the plug, try to remove it when the part is around 200° F for the same reason as when using tape. You’ll get cleaner edges and have fewer defects.

Improve Your Powder Coating With Quality Equipment

Your finish quality is tied directly to the tools you use. If you’re going to be doing professional quality work, you need professional quality powder coating equipment. Reliant Finishing Systems only partners with premium quality, brand-name powder gun manufacturers like Wagner. We only integrate premium component for use with powder coating booths and powder curing ovens.

Looking to upgrade your powder coating results? Let Reliant help you with the equipment and support you need. Give us a call today.

Proper Grounding Techniques for Powder Coating

Powder Coated Parts After CuringOne of the keys to successful powder coating application is proper grounding. A good ground acts like glue to the powder being sprayed on the part, making it easy to get a uniform, high-quality finish with high transfer efficiency. A weak ground can cause a host of issues, such as light coverage areas, Faraday cage problems, larger hook marks, generally uneven powder application, dirtier spray booth filters, and poor transfer efficiency. In extreme cases, improper grounding can cause the operator to get shocked.

How to Get Proper Grounding for Your Powder Coating Gun

There are four main areas where your grounding technique needs to be addressed:

Grounding Rod. We have mentioned in previous articles that the best starting ground for manual spray applications is a 6’ to 10’ copper grounding rod installed just outside of the powder spray enclosure. Permanently attach a ground strap of at least a 14-gauge wire with a good clamp on the end that will be used to ground parts. When the ground rod is in rather sandy or dry soil, a small amount of water can be poured into the grounding rod hole and allowed to soak in prior to powder coating.

Clamp And Copper Grounding Rod For Powder Coating

For the best ground, make sure your clamp (left) is attached to a copper grounding rod outside the spray booth (right).

When using this grounding method, the powder will stick to the part like glue. The powder will resist being shaken off when moved or when encountering mild air movement.

IMPORTANT: Using just the grounding clamp supplied with the gun unit is inferior to using a grounding rod, but it’s better than nothing until you get your grounding rod installed.

Parts Rack or Cart. You will need good metal-to-metal contact from the grounding rod clamp to the part. If you clamp the cart in the same place each time, be sure to blow or wipe off the powder around the clamp attachment area each time BEFORE the cart enters the curing oven. This will prevent you from having to grind off this area every time you use the cart.

Custom Parts Racks For Powder Coating

When parts are attached directly to the rack or cart frame, metal-to-metal contact is usually achieved by the part shielding the rack’s contact points. It’s important to note that if you do not hang parts on every contact point, powder will accumulate on the exposed points and will have to be removed before using the rack again. Some operators use high temp tape or other masking agents to protect areas of the rack from powder that can become baked over the exposed metal.

If you use racks that have movable hooks to attach the parts using a bar or similar contact points, you need to grind the tops of the bars every 5-6 coating cycles. This will ensure a good ground and proper transfer efficiency. If you hear popping sounds while applying the powder or see small instances of electrical arcing from hook to rack, flag that rack to be cleaned via grinding or stripping before using it in the next coating cycle.

Racks can usually be manufactured by any local metal fabrication shop. Many job shops make their own. When designing racks or carts, remember to concentrate parts so they are two feet from the floor to about six feet high. This will allow the operators to spray all areas fairly easily.

HParts Being Powder Coated On Hooksooks. As with the cart, you need good metal-to-metal contact with the cart and the parts. Most shops can get 5-6 uses from a hook before it starts becoming insulated by baked-on powder. Some powder coaters just replace the hooks with new ones, but others have them cleaned. Cost analysis will tell you which is more efficient. If you are getting arcing and the rack has been cleaned, then you need to clean or replace your hooks. Mighty Hook is a great source for hooks, plugs, and tape. http://www.mightyhook.com/default.aspx

Parts. Not all parts ground well. Because of their mass, some parts can be tough to ground properly. Also, if parts have been coated before, they can be more challenging to ground. Sometimes the racks don’t ground parts adequately because the parts hang too far from the grounding point. In these cases, you can clamp directly to the part in question. After spraying the powder, just remove the clamp and spray the clamped section last to keep from getting surface defects.

If you’re worried that you might not be getting a good ground, use a megohmmeter (often called a “megger” after the company that makes these types of test instruments: http://us.megger.com/) to check the resistance from area to area. If the resistance exceeds 1 megohm from ground to part, work backwards at all the contact points to determine where the loss of ground is occurring.

Using professional quality powder coating equipment can solve many of your coating issues. All of Reliant Finishing Systems’ equipment is designed to provide the best finishes possible for today’s powder coating operations. Find out more about Reliant equipment here, or give one of our systems specialists a call today.

Tips For Touching-Up A Powder Coated Finish

Pump Casting With Powder Coated FinishOne of the many advantages powder coating has over wet paint is the variety of ways you can fine-tune and rework a powder coated finish. This article discusses some of the different touch-up techniques you can use to clean up your work and get the best overall quality for your powder coating projects.

Why Should You Touch-Up Your Powder Coated Finish

Visual Appeal. This is the obvious reason for fixing a powder coated finish. To most customers, if it doesn’t look right, it isn’t acceptable.

Performance. Some powder coatings are purely functional, so they don’t need to be aesthetically perfect. Usually there are one or more standards (such as corrosion resistance) that have to be met. A defect can compromise the finish integrity and cause a part to fail to meet a specific customer’s standards.

Warranty. If the powder coated part has any sort of warranty, then special care should be made to make sure the part passes end-of-the line QC testing. A part may look great and have no apparent defects, but if it does not pass the customer’s minimum testing standards, a repair or rework is needed.

When Is The Right Time To Do Touch-Up Work?

The best time to catch your coating mistakes is prior to curing the powder. The powder can easily be blown off with compressed air or wiped off and then reapplied with very little hassle. Get in the habit of checking your parts for application errors before you start the curing process. Every mistake you catch here will save you time, effort and money later.

Common Powder Coating Touch-up Techniques After Curing

It’s not always possible to catch coating errors, especially if there are overbaking or underbaking issues with your oven. When dealing with a defective finish, you should ask yourself: will a touched-up surface be acceptable -both visually and from a performance standpoint-or should you repaint? In either case, if you have to resolve a finish problem, here are some of the most effective techniques to use once a powder coated part has been cured using Reliant’s products:

Liquid Paint Touch-Up

Many manufacturers use color-matched liquid enamels to cover hook marks, missed areas, Faraday areas, re-welds, sanded spots, handling damage and other defects.

Pros – cheap, fast, least labor intensive, little skill required

Cons – not visually appealing on a class A part, visual “halo” around repair, repair is not as durable as the rest of finish, repair may fade or chalk faster than surrounding powder coated finish

Usable with most decorative finishes. This repair method is fine except for on the primary surface a customer can see.

Re-coating

In some instances, your powder process can allow for a repainted finish to go over a previously painted part with no prep work. Usually the part must be freshly powder coated with no contamination on the surface.

Some chemistry is not compatible with this method and the surface will need to be abraded (blasted with abrasive grit or scuffed with sandpaper) and then wiped down with alcohol. If the part has been cured for more than a week, it will almost always need to be abraded and cleaned before re-coating. 

Pros – Less expensive and faster than stripping, better corrosion protection than liquid enamel

Cons – Adhesion risk (always do a test part and check adhesion), too much film build-up could cause issues (weight, measurement tolerances, extreme temperature checking)

Many small parts manufacturers will re-run parts after inspection if they have light powder coverage or other easily repaired surface defects. In the closet hardware and racking industries it is especially common for facilities to repaint parts once or twice if they are having an acceptable amount of rejects.

Tip: Remember to use your powder gun’s re-coat settings to properly apply a second coat

Sanding And Buffing

Sanding and buffing the powder finish can eliminate surface trash and some defects. This also helps smooth out orange peel that naturally occurs with most powder coatings on parts where the powder thickness is excessive in a particular area. Sanding companies like 3M have a series of abrasive and buffing compounds that allow shops to sand out defects and then bring the surface back to a smooth shine.

Pro’s – Mirror-like finish, faster to buff than to repaint

Con’s – Burn-throughs will need to be repainted or touched up with a liquid paint, labor-intensive, requires moderate skill

In the automotive and other transportation industries, manufacturers will sometimes sand and buff out Class A type parts such as hoods or panels that need to have a mirror-like defect free finish. This is similar to work done with wet paint. It takes some experimentation to develop a successful sanding and buffing process.

Tip: The sooner you buff after curing, the easier it is to work with the finish. Power coating gets very hard 1-3 days after curing.

IMPORTANT! Be sure to have the buffing operation isolated from the finishing operation. Many of the waxes and compounds used for buffing and polishing do not react well with painting and powder coating processes and can cause defects like “fish-eyes.”

 Fillers And Putties

There are many products like Bondo and Lab-metal that can be used to fill gaps and seal holes prior to powder coating. Before adding a filler to your process, make sure it is compatible with 400° to 450° F curing temperatures and that it is recommended for powder coating.

Pros – Eliminates re-welding for small areas, surface defects are much less noticeable if repaired prior to powder coating, parts do not need to be taken off-line for repair

Cons – Powder may have trouble being electrostatically attracted to the repair, in a large area adhesion can be suspect, may cause powder finish to “shimmer” or look different over repair

Trailer companies often use filler-putty to bridge gaps in their dump-style trailers. Tiger Drylac has a two-component filler that has some conductive elements for good results when used under a powder coated finish. Here is a link to their data sheet:

http://www.tiger-coatings.us/fileadmin/user_upload/downloads_us_new/product-data-sheets/tiger-drylac/special-products/Epo_Strong_Series_93-70080_Epoxy_Repair_Kit.pdf

Total Strip And Repaint

If there is a catastrophic finish failure, starting over after taking the finish off down to the bare metal can sometimes be the only solution. Major powder coating issues, like severe adhesion problems in high-performance parts, often require a total repaint. Pretreatment failures, parts contamination after pretreatment, underbaking, and overbaking can also cause problems that are so bad that the only answer is to totally strip the coating off and redo the process (after you have identified and corrected the fault in the process). Remember, the finish is only as strong as its weakest layer, so if you notice flaking once the finish is cured, it will need to be completely redone.

Pros – Once the process is fixed, you have high quality parts going to the customer and you don’t have to worry about field failures and the possibility of costly claims in the future

Cons – Costliest and most time-consuming solution

For demanding projects like government contracts, high-performance industrial components, engine parts, military equipment, parts that will be exposed to a highly corrosive environment or impact/abrasion in the field, the only way to insure quality compliance for parts that have badly defective finishes is to re-work the parts down to the metal.

The Nail Polish Fix

We’ve just outlined the most common touch-up and re-work methods, but there is another technique that can sometimes get positive results. An uncommon method for fixing small finish imperfections is to put a small amount of the powder in a clear lacquer and use it as touch-up paint. It’s possible to use hair spray, nail polish and other lacquers in a hobby situation, but bulk materials will be needed in a professional environment. Although the touched-up area will visually match the cured powder paint, the repaired area will not have the same durability as the cured surface. Remember, if you need the same surface integrity and durability in your touch-up areas as you do with the powder coated finish, you will probably need to use a two-component catalyzed topcoat and possibly a zinc-rich epoxy primer for appropriate corrosion resistance.

Meet Expectations With The Right Powder Coated Finish

To retain business and keep customers happy, you need to know exactly what each customer expects from the powder coated finish you are providing. Once you know that, you can develop a process that includes a repeatable touch-up system that addresses defective finishes of all types. Proper touch-up and re-work techniques help ensure great finished products.

Using professional quality equipment can solve many of your coating issues, including overbake and underbake problems associated with outdated or inferior quality ovens. All of Reliant Finishing Systems’ equipment is designed to provide the best finishes possible for today’s powder coating operations. Find out more about Reliant equipment here, or give one of our systems specialists a call today.

Understanding Powder Coating Gun Settings

When you first start powder coating, adjusting your powder coating gun settings can be confusing. We’ll cover the most important terms and settings for everyday powder coating situations and addresses some common issues you may encounter. Once you understand how electrostatic powder guns work and know what the basic gun settings do, you can improve your powder coating results quickly and confidently.

Author’s Note: All examples in this article use the Wagner EPG controller for illustrative purposes, but other brand-name professional quality guns have similar controls.

Powder Coating Gun Settings # 1: Kilovoltage (kV)

Powder Coating Gun kV Meter“kV” is the symbol for kilovolt. One kilovolt = 1000 volts. It is a unit of measure indicating how much electrical charge an electrostatic powder gun can produce.

The kV adjustment changes the amount of voltage charging the powder particles as they pass through the gun. The higher the setting, the stronger the charge. High settings are great for flat panels and the outside of box-like parts. A high kV setting can improve your transfer efficiency (more powder sticks to the part) and also allow you to increase the distance between the gun and the part. This can help you get very uniform coverage on flat surfaces. In some cases, excessively high kV settings can cause tiny pits or dimples in the finish due to “back-ionization.”

Lower kV settings are best for Faraday cage areas and when working with some specialty powders, such as metallics. As a general rule, the more detailed and complex the part, the lower the kV setting. Professional quality powder guns from companies like Gema, Nordson and Wagner typically have a maximum voltage setting of 100 kV. A good starting point is a setting of 50 to 80 kV for applying a single coat (or the first coat) to an uncoated part. When working with Faraday cage areas, turn down the voltage. When applying a second coat, a lower kV setting can give the best results.

What is the Faraday Cage effect? This describes what happens when you are trying to powder coat into a recessed area like the inside of a box. Highly charged powder particles are attracted to the closest grounded metal surface–the sides of the box–so they have a difficult time penetrating into the corner. This often happens with parts that have tight corners, angled features, prominent bends or recessed areas. Window and door trim, frames, boxes, wire racks, I-beam sections, angle iron, conical parts, u-shaped channels, uni-strut, grids, and other unusually shaped parts can be tough to coat without adjusting the gun’s output. By reducing the electrical charge (lowering the kV setting), you can help sprayed powder penetrate Faraday cage areas more effectively.

It is important to have a good ground. This is the physical connection that allows an electrical current to follow a path to earth. A ground is needed for the charged powder particles to effectively be drawn to the metal part. The stronger the ground, the more effectively the electrostatic process works. We recommend the use of a dedicated grounding rod. Get a copper grounding rod of at least 8’ length from an electrical supply company. Drive the grounding rod into a spot as close to your powder spray booth as possible (yes, you will have to penetrate your concrete floor if you have one). Using a good quality grounding strap of 14 gauge or heavier wire (heavier is better) and a well-made clamp, connect the ground rod to the rack or hook that is supporting your part. This will dramatically improve the performance of your coating gun, especially when dealing with complex parts. In some areas, you may need to pour a few ounces of water into the hole around the grounding rod to improve the quality of your ground.

Another way to improve results in Faraday cage areas is to aim the gun near the corner or detail area, but not directly at it. Wrap is the term that describes when sprayed powder is attracted to the back side of the part. Wrap means that the gun delivers powder to areas of the part that aren’t directly in front of the gun’s output. By having a good quality ground, you can get improved wrap on panel-shaped parts and improved penetration into Faraday cage areas.

Remember, voltage and amperage are not the same thing, so it may be important to also adjust the amperage at which the powder is being sprayed.

Powder Coating Gun Settings #2: Microamperage (µA)

Powder Coating Gun Microamperage Meter“µA” is the symbol for microampere. One microampere = 1/1,000,000th of an ampere. It is a measurement of electrical current. It indicates how much charge is moving from the gun’s electrode to the cloud of air and powder exiting the gun, and then onto the surface of the part being coated. This may be the hardest gun feature to understand.

Voltage and current (measured in microamperes) have an inverse relationship when you’re talking about powder coating guns. Voltage is a measurement of electrical “potential to do work,” while current is a measurement of the actual movement of electricity–“the work being done.” When some of the potential energy is used, it becomes current. As current increased, there is less potential (unused energy) left. A gun’s current feedback system can indicate to the operator what the electrostatic charge is doing. It is, in some ways, more useful than just looking at the kV setting. This is because the microamperage reading tells you how much of the charge is working, instead of just indicating the charge’s maximum potential like the kV setting does. On powder guns like the one shown from Wagner, you can see the effectiveness of the charge and limit how much current is possible. This allows you to understand and control how much energy is being used.

The kV setting is, in part, restricted by the power supply. While spraying a part, the load on the power supply limits the actual output, so the voltage may be lower than the setting. The current load increases as the gun gets closer to the part being sprayed. On a gun with an adjustable current limiter, when the current load reaches the set limit, the kV will quickly decrease. This helps prevent problems from too much voltage (like dimples in the coating from back-ionization), especially when the gun is too close to the part. Also, if the amperage is not limited to a certain range, the transfer efficiency may suffer in Faraday cage areas or the powder may not coat evenly if the gun-to-part distance is inconsistent. Setting the µA range to 20-25 can help with difficult to coat areas.

Powder Coating Gun Settings #3: Air-Flow/Powder Volume Dial

Powder Coating Gun Air-Flow DialWagner powder application guns automatically balance the powder output with the airflow via the main dial. The number selected is the actual maximum percentage of powder that can be used. Typically, 70% is the highest you would want to go. When working with intricate parts, this number can be much lower.

 

 

Powder Coating Gun Settings #4: The Factory Presets

Powder Coating Gun Factory PresetsThese are settings pre-determined by the gun manufacturer or the operator. They are intended for the most common scenarios encountered by typical gun users.

Flat Panel Setting: This setting provides maximum kVs and a high volume of powder being sprayed. This is for large flat panels and will provide a lot of powder wrap.

Repaint Setting: This setting is for a previously painted part that needs more powder for cosmetic or performance reasons. The kVs are reduced, as is the powder volume, since there is already powder on the part.

Faraday Cage Setting: This setting lowers the kVs, restricts current µAs, and reduces the powder flow percentage to allow powder to penetrate difficult-to-reach corners and angles.

Custom Settings: These are the settings that you use with a specific powder or part. The fourth preset is reserved for custom settings. (On the Wagner controller, you have up to 50 available custom settings that can be saved.)

My Powder Coating Gun Is Set, Now What?

Once you’ve got your powder gun adjusted correctly, you are ready to start spraying powder. Before you begin coating a part, look at the part and figure out how you will get the best and most efficient coverage while spraying. As your part becomes coated with powder, a charge will build up on the surface. It will make the Faraday areas even more challenging to coat. Therefore, it is best to coat the Faraday areas first, then spray the flat surfaces of the part.

After rehearsing what you are going to do, you need to get the powder flowing smoothly through your gun. Spray the powder coating gun away from the part until a uniform cloud is coming out with no sputtering or surging. This may take up to a second or two. Move the gun to the part and move it in a slow, controlled motion across the part, keeping a gun-to-part distance of around 8”. Keep the gun triggered and spraying until the part is done—don’t start and stop. If possible, try to get full coverage with a single pass across the entire part. Often you will need to move the gun in a controlled back-and-forth motion, starting with side-to-side movements and then switching to up-and-down passes if needed.

Inspect the coated part with a bright light to help detect thin spots. Touch up any spots you see before curing the part, but be careful not to add too much powder or to let the gun puff powder onto the touch-up areas. These common mistakes happen when you become impatient and blast the part with a heavy fog of powder or don’t let the gun’s powder flow stabilize before attempting touch-up work.

What Else Do I Need To Know?

Air Supply Problems are not uncommon. It is critical that you use only cool, dry, oil-free compressed air to power your powder application guns. Make sure you have an accurate in-line pressure gauge and a regulator that can restrict the amount of pressure reaching your gun. You may need to use a powered air dryer, and you will definitely need a filter system that traps moisture and oil.

Fluidization is what we call the small amount of air movement that aerates and fluffs the powder around the pick-up tube on a box-feed unit. An adjustable valve controls how much air is provided. The air helps break up clumps of powder before they are pulled into the pick-up tube and pumped through the gun. It is also the term used for the air movement that mixes the powder in a hopper container. In the hopper unit, there is a plastic membrane at the bottom with lots of tiny holes that allow the air to condition the powder. When adjusted correctly, it will look like the powder is slowly boiling.

Impact Fusion describes what happens when partially gelled powder sticks to sharp areas in the gun and inside the powder pump. This problem is more prominent in hot shop environments and when working with poorly conditioned powder. The stuck-on powder can be removed with a clean, fresh shop towel and denatured alcohol.

Mil Thickness is the term used when talking about the thickness of the powder coating material that has been cured over the surface of a part. One mil = 1/1,000th of an inch. A healthy human hair is about one mil thick. Most powder coated finishes are between 2 and 4 mils thick, with some finishes up to 6 mils or thicker. Achieving ideal powder thickness and uniform coverage takes practice. Make sure to keep good notes. Some coating instructors have their students spray test parts to learn about adequate powder coverage. A student sprays a part while the instructor illuminates the surface of the part with a bright pocket flashlight. Once the flashlight no longer reveals any bare metal spots, the student stops spraying. This method typically results in a finished coating that is about 2 mils thick.

Orange Peel describes the uneven, “wrinkled” finish that can happen after curing if the painter sprays too much powder on the part in some places. You can end up with areas of heavily concentrated powder that flow out into wavy sections that have something of an orange peel texture. The excessively thick powder in these areas will also make the finish more prone to chipping. If the applied powder is under-cured, especially as the result of the oven temperature being too low, the powder can also fail to flow out properly, even if it’s not too thick, causing the same type of textured defect in the finish.

Powder “Starved” Finish/Light Powder are terms used to describe the grainy texture that a defective finish can have after it is cured if the part does not get adequate powder coverage. If there wasn’t enough powder on the part for it to flow together and create a uniform coating, it can have an odd, textured appearance. Even worse, the part will likely start to rust or oxidize in these textured areas because the part’s surface isn’t fully covered by the coating material. Using a powerful flashlight or LED inspection tool can help prevent this by allowing the painter to see areas that need more powder.

A professional powder coating gun can make a huge positive impact on your operation, allowing you to coat with more accuracy, better efficiency and higher quality. Reliant Finishing Systems only offers professional powder guns from companies like Wagner. Need a new powder application gun or a complete powder coating system? Our powder coating specialists are ready to help – give us a call today!

The Basics Of Powder Coating Coverage

Powder Coating Gun And PartKnowing how much powder you need for a particular job is critical when determining cost. Without that information, it is easy to make pricing mistakes that can drain your profits or run off potential clients due to pricing that isn’t competitive.

However, calculating powder cost can be a little confusing. We’re going to show you how to calculate powder coating coverage and how to gather the information necessary to give an accurate prediction of cost per square foot.

 

The Data You Need To Calculate Powder Coating Coverage

Before you start calculating coverage costs, these are the values that you will need to know :

  • Powder Specific Gravity
  • Cost Per Pound of Powder
  • Transfer Efficiency
  • Dry Film Thickness
  • Square Footage of Metal To Be Coated (Per Part)

Powder Specific Gravity: This is usually supplied by the powder coating manufacturer on their technical data sheet. Remember that not all powders of the same color have the same specific gravity.

Cost Per Pound of Powder: Check your invoice or get the cost from your powder manufacturer or sales representative.

Transfer Efficiency: Transfer efficiency is the percentage of the powder that is being applied to the part instead of being wasted as overspray. Transfer efficiency is almost always an estimated figure and the most difficult one to determine when estimating coverage costs. It is hard to get an accurate percentage of how much powder is being applied to the part and how much is going in the filters, on the floor, on the rack, and getting stuck to the booth’s walls.

Powder Coating Gun Overspray

Transfer efficiency is directly impacted by how much powder the operator is using.

Transfer efficiency is directly related to the way the operator is applying the powder. If there is a giant cloud of powder in the booth or a heavy fog of powder blasting out of the gun, you can bet that there is more wasted powder than if the operator is spraying lightly enough to coat the face of the part and still get a gentle wrap of powder moving around the part to partially coat the other side.

Proper ground and powder coating gun quality can have a significant effect on transfer efficiency. A shop with a dedicated ground rod that is connected to the parts rack or hooks, or to an uncoated portion of the parts, can always get better transfer than one that doesn’t. Likewise, a shop using a professional quality electrostatic gun with adjustments for powder flow, voltage and current can get better results than one using a hobby gun.

For estimation purposes, if this is a new operation with untrained painters, the transfer efficiency can be as low as 25%-30%. After proper instruction, experience, gun adjustment, and proper ground, the transfer efficiency can reach 70%. If you are reclaiming the powder by collecting and reusing the powder, you could possibly reach 85%.

One way to calculate transfer efficiency percentage is to determine how much powder is applied to a part in the time necessary to fully coat that part. You will need a high quality digital scale and a timer to do this. First, weigh your part before you spray it. Get your timer ready and spray the part until it is fully coated and ready to cure. Record the time it took to coat. Now, weigh the part again to learn how much powder was deposited. Next, turn off the gun electrostatics but do not adjust the powder flow or air and spray the powder gun into a porous filter bag that will trap the powder but allow the air to flow through (you can get these online or from your powder supplier). Spray powder for the same length of time it took to spray the part. Weigh the bag before and after to measure how much powder was applied. Then apply the following formula:

Powder Deposited (the weight of the powder on the part) divided by Powder Applied (the weight of the powder in the bag) multiplied by 100 will give you the basic transfer efficiency percentage.

Powder Coating Gun Applying PowderDry Film Thickness: This is the amount of powder you would like to apply to the part, measured in terms of coating thickness. You can measure a part with a DFT gauge to get an average of the mil thickness across a section of the part’s surface. You should take as many readings as possible, then average them, to get the most accurate estimate of the overall average thickness.

Square Footage of Metal in Your Part: This might take a bit of calculation but it will give you the cost per part at the end of this exercise.

Powder Coating Coverage Formula

Now that you have all the data you need, you can apply the powder coating coverage formula.

Assumption: The Powder Coating Industry standard is 192.3 square feet of coverage per pound of powder. This pound of powder would be at 1.0 specific gravity and applied at a thickness of 1 mil with 100% transfer efficiency. In other words, this is how much surface a common powder could cover if no powder was wasted and you only needed a thickness of 1/1000th of an inch.

So the formula would be:

Actual Coverage Rate (ACR) = 192.3/Specific Gravity/Mils x Transfer Efficiency (as a decimal)

Example: Powder A has a 1.5 specific gravity and is being sprayed at 2 mils with 50% transfer efficiency. The powder cost is $5.00 per pound. The part being sprayed has 3 square feet of surface area.

ACR = 192.3/1.5 (specific gravity)/2 (mil thickness) x .50 (transfer efficiency)

ACR = 32.05 square feet per pound of Powder A

Next, take your cost per pound and divide it by your ACR.

Cost per square foot = $5.00 (cost of one pound of powder)/32.05(ACR) = cost is $0.16 per square foot of coverage by Powder A

Multiply this cost by the square footage of your part’s surface area and you’ll know the cost of the applied powder.

Cost Per Part = 3 (square feet of part) x $0.16 (cost per square foot) = $0.48 per part in powder cost

Now that you know how to do this by hand, Interpon has a nice online calculator that you can use here: http://www.interpon.us/our-coatings/powder-coverage-calculator/

Knowing what your cost is for powder coverage will prevent you from making costly budgeting mistakes and keep your prices competitive.

Powder Coating Gun For All ApplicationsIn order to maximize your profits you have to maximize your transfer efficiency, and the best transfer efficiency comes from professional powder coating guns. Professional guns provide multiple settings and factory-presets to get the right amount of powder onto your parts without excessive waste. Reliant Finishing Systems only provides professional quality powder application guns from industry-leading companies like Wagner. When you buy from Reliant, you know you’ll be getting the gun you need to get the job done right.

Looking for a new powder coating gun or new powder coating system? Give us a call today – our systems specialists are standing by to answer your questions and help improve your operation.

Manual Powder Coating Gun Comparison: Box-Fed vs Hopper-Fed

Venturi Pump - Wagner Manual Powder Coating Gun

Typical venturi pump from a Wagner manual powder coating gun system.

If you’ve been shopping for a manual powder coating gun, you’ve already seen the terms “box-fed” and “hopper-fed.” In this article, we’ll explain what those terms mean, how they affect your powder coating process and how picking the right gun configuration can dramatically improve your results.

Every professional quality manual powder coating gun has an integrated delivery system for preparing the powder and bringing a steady stream to the application gun. The powder flows through the hand-held application gun as it is sprayed onto the part being coated. Both box-fed and hopper-fed delivery systems provide powder to a venturi-type powder pump, but these two preparatory feed systems have different attributes. You’ll need to consider which system will work best for you before buying a new powder coating gun.

[Author’s note: We’re showing Wagner products for this article, but other brands look very similar.]

Box-Fed Powder Coating Guns

Wagner Box-Fed Manual Powder Coating Gun

Wagner box-fed powder gun with pick-up tube shown outside of a box of powder.

A box-fed powder coating gun draws powder coating media directly from the box provided by the powder supplier. A platform holds the powder box at an angle on a stand below the gun’s controls. A powder pick-up tube is then inserted into the powder in the box. The pick-up tube hangs vertically and usually has a small amount of compressed air delivered to the tip area to break up any compacted or clumpy powder. This helps assure uniform powder flow. The tube routes the powder up to the venturi powder pump, which sends the powder to the gun itself.

During operation, the platform which holds the box constantly vibrates. This vibration causes the powder to shift around inside the box. The powder in the box moves constantly and replaces the powder that is being pulled up the tube. This prevents “rat holes” from developing in the powder still in the box. Without constant vibration, the powder would be supplied in surges, which would create problems during application and degrade the finish.

Advantages of Box-Fed Powder Coating Guns

1) Fast Start-Up: Grab a box, open it up, put the pick-up tube in and start coating!

2) Quick Color Change: It takes as little as 3-5 minutes to change colors when using a box-fed gun with air pulse cleaning. Less expensive models may require up to about 10 minutes. You simply clean or swap the hoses, switch to a different box of powder and go back to work.

3) Lower Initial Investment: If you spray a variety of colors and textures each week, the cost of buying multiple hoppers can really add up. Since the powder you buy already comes in a box, there is no extra cost associated with dealing with lots of different powders.

4) More Mobile: There’s less weight to move around your shop when working with a box instead of a hopper on the gun cart.

Disadvantages of a Box-Fed Powder Coating Gun

1) Special Effect Powders Won’t Work: Since the vibratory box feed system tends to cause larger or denser particles to settle to the bottom of the box, any powder that has distinct particle size differences can have consistency issues, especially as you get closer to the end of the box.

2) Humidity Can Cause Problems:  To get best results and prevent powder from degrading while in storage, you should keep your powder in a cool, dry, climate-controlled area. If you are starting a new project and you bring powder into a hot and humid shop environment, you can encounter troublesome powder clumping due to condensation occurring when the cool powder is exposed to the humid air.

IMPORTANT:  When working in hot or humid environments, bring out a box of powder a couple of hours before you need it and open the top to allow the powder to acclimatize to the environment before you start spraying with it.

3) Spillage And Contamination: Although it isn’t easy to do, you can tilt the gun cart by accident and spill the powder out of the box. You can also get contaminants in the powder if you try to reuse spilled powder, or if you have a dirty shop environment and leave the opened box of powder in use for a long period of time.

Hopper-Fed Powder Coating Guns

Powder Coating Gun - Wagner Hopper Fed Gun

Wagner hopper-fed powder gun with powder pump attached to a 60-liter stainless steel hopper.

A hopper-fed powder coating gun holds the powder in a sealed (usually stainless steel) container that has a perforated plastic membrane on the bottom. This membrane has tiny holes in it that allow compressed air to enter the container and constantly fluff the powder so that it flows around inside the hopper. This process is called fluidization. When you look at the top surface of the powder in a hopper that is being fluidized by compressed air, it should look like it is boiling. If you put your hand in the powder while it is being fluidized, it should feel silky smooth.

The compressed air supply to the hopper should be adjusted so that powder isn’t wasted due to excessive agitation/over-pressurization of the container. While some powders require a small amount of venting, you should adjust your system for minimal powder loss, especially if you are reclaiming the powder as an on-going process.

Specific Advantages of Hopper-Fed Powder Application Guns

1) Conditions The Powder: The fluidization process helps remove moisture in humid environments by introducing clean, dry air from the bottom of the hopper.

IMPORTANT: Never stir the hopper with a stick! It can damage the plastic membrane on the bottom of the hopper, reducing the effectiveness of the fluidization airflow.

2) Mixes The Powder: Fluidization also insures that the powder is thoroughly mixed. This is important if you are regularly spraying river textures or bonded metallic powders, or making a transition from one batch of the same powder to the next.

3) Less Chance of Powder Contamination: The hopper is sealed off from the surrounding environment and each hopper is typically used for only one type of powder.

4) Less Surging: Because the powder is better conditioned, the pump picks up the powder more consistently and the gun delivers it more uniformly.

Disadvantages of Hopper-Fed Coating Guns

1) Increased Cleaning Time: If you have only one or two hoppers for all of your colors and textures, it can take a significant amount of time to switch between colors or textures—up to one hour per change if done meticulously.

2) Cost/Storage Issues: If you buy multiple hoppers to accommodate all of your most commonly sprayed powders, it can be costly. It can also be challenging to store hoppers when they are not in use. You may end up using valuable floor space to store empty hoppers, particularly if you don’t normally carry some common powders in inventory and get them on demand from your powder vendor.

3) Reduced Throughput: If you commonly have to move the cart around a good bit because of the size or complexity of what you are coating, having a hopper-fed gun can slow you down. A gun cart loaded with a full 60-liter hopper (the most popular size) can be a bit unwieldy.

Which Powder Coating Gun Is Right For You?

Depending on your work environment, getting the right configuration can make a significant impact on your performance. If speed (how fast you can get started on a new project), agility (how fast you can change colors or textures) and lower cost are key concerns, a box-fed gun may be the right choice for you. If premium finish quality is the most important goal, a hopper-fed gun is probably the right tool for the job.

Box-fed powder coating guns are best suited for:

1) Job Shops: If you spray different powders for different jobs, guns that are box-fed let you change colors quickly between projects.

2) Regular Powder: If you don’t do a lot of special effects, box-fed guns work fine with most single color powders.

3) Small Powder Runs: If you only powder coat a small number of parts the same color during the week, a box-fed unit is perfect for projects where you’ll only be running a few pounds of a specific powder at a time.

Hopper-fed powder guns are recommended for:

1) Limited Color Applications: If you only use a handful of different powders, a hopper-fed gun is usually a better value.

2) Special Effects: As noted before, if a special effect powders are an important component of your process, having a hopper dedicated to each of these powders would be best. Special effect powder must remain fluidized to be applied properly, and a box-fed system simply won’t cut it if you need professional quality results.

3) Reclaim: If you reclaim your powder, you’ll need a hopper-fed gun. The hopper-fed system enables you to mix reclaimed powder with new virgin powder perfectly.

IMPORTANT – If you are new to reclaiming spent powder, a ratio of 60% virgin to 40% reclaimed powder is a good starting point.

4) Humidity Issues: If your powder’s characteristics or your shop environment causes clumping due to humidity, using fluidized hoppers will usually cure this issue if you have an air dryer attached to your shop’s compressed air supply.

With either feed system, you can be successful powder coating a wide range of substrates with multiple types of powders. If you decide on a box-fed system first, you can always add a hopper later. With most professional quality systems, a hopper can be attached right to the box feed controller and only requires a small fluidizing air tube attachment. Although it may cost a little more to have your gun configured this way, it enables a single gun to give you the benefits of both systems.

Have questions about powder coating guns? Looking to add a new gun to your existing coating operation? Feel free to give us a call. Our systems specialists will be happy to help you get the powder coating gun you need.

Using Iron Phosphate To Get A Better Powder Coated Finish

Pic for steam unit pageWe’ve talked a lot about pretreatment in previous articles: why it’s important to get your parts clean and what pretreatment options you have. But from a production standpoint, why is pretreatment important? Why add another step to your powder coating process? We’ll examine this using one of the most commonly powder coated materials: steel.

If you are powder coating, chances are that at some point you’ll be powder coating steel. Powder is easily applied to steel parts and generally provides a good finish. But what if you need the powder coating on your steel parts to last longer or to be more wear-resistant? You may be providing parts that will be subject to high-impact or are handled regularly, or parts that must last a certain amount of time. Simply applying the powder and curing the part won’t achieve the result you or your customers need. In order to get those results, you’ll need to add a pretreatment step before you apply the powder.

One of the most popular and effective forms of pretreatment for steel is iron phosphate. Iron phosphate is a conversion coating that provides a barrier against oxidation. It is most effective on bare (uncoated), clean steel.

How Can Iron Phosphate Improve My Powder Coated Finish?

Adding an iron phosphate stage to your pretreatment can dramatically improve the quality and longevity of your powder coating.

Iron phosphate provides increased adhesion. This is especially useful for slick surfaces. Iron phosphate pretreatment causes a small amount of surface material to be deposited on the parts being treated. This material is slightly textured so the powder can grip it. If the parts are occasionally bumped during their use, this improved adhesion is especially helpful because it keeps the coating intact.

Iron phosphate provides increased corrosion resistance. Most powders provide a salt-spray rating of 250 hours on clean metal, but what happens when the protective powder coating is scratched or worn? Phosphate adds a second layer of protection and can extend the salt-spray rating to 500-1500 hours, depending on the process.

How Can Iron Phosphate Be Applied?

There are a number of different ways to apply iron phosphate to your parts before you apply the powder coating.

Hand wipe: While not very efficient or consistent, there are chemicals that can be hand wiped on and then rinsed off to form an iron phosphate layer.

Hand spray: Professional quality wand systems, also known as spray wands, are very good at delivering iron phosphate chemicals to the surface of most parts. Iron phosphate works well with heat, so gas fueled or electrically heated sprayers work best. These sprayers may include pressure wash, wet steam or dry steam features. A rinse/seal step is often required as part of the process to prevent streaking or chalking that can interfere with the powder coating. Spraying is often done inside a stainless steel booth, often called a manual wash station, and/or may take place over top of a grated wash stage that allows spent chemistry to be contained and potentially recycled.

You can see a hand-operated spray wand in the video by Electro-steam below:

Dip: Heated chemical vats, also known as dip tanks, are a great way to pretreat baskets of small parts that have hard to reach areas. This often involves multiple stages performed in a series of tanks with rinse stages in between.

Automatic spray: This is generally the most effective and consistent way to apply iron phosphate chemistry, but it is also the most expensive. Multi-stage spray systems are typically part of an automated coating line where the parts travel by conveyor at a pre-set rate. A multiple stage pretreatment system can have as few as 2 stages or as many as 8 or more stages. For higher-end architectural finishes, multiple applications of phosphate create an excellent corrosion barrier and other agents in the chemistry clean the part to allow for nearly defect-free parts when powder coating is applied.

Where Can I Find An Iron Phosphate Supplier?

Search online for companies like Bulk Chemicals, Chemetall, Dubois, or Houghton. These companies and others can provide you with information about local suppliers or will have a local distributor contact you to help you select the proper chemicals.

Your local powder supplier can suggest a chemical supplier who will have products that work well with the powders you are using.

Thomas Register & related industry guides may also be able to provide you with an iron phosphate supplier. You can get a lot of information from industry guides like Thomasnet.com, but you may have to play around with your search settings to find companies that will do business on a smaller scale.

As a general rule, avoid online outlets that cater to the hobbyist and DIY markets. They may have chemical products of inferior quality or from sources that vary from batch to batch. Parts preparation is one of the most important steps in the coating process—don’t risk costly reworks by using cheap, no-name chemistry sold online by the bucket.

Have any questions on pretreatment? Need to add pretreatment to your powder coating operation? Reliant provides blast rooms and wash stations for use with your existing equipment, or we can implement your pretreatment requirements into the design of your new coating system. Whatever you need, from hand-wash spray units to fully automated wash stations, Reliant Finishing Systems can provide a quality system at an unbeatable price. Call one of our system specialists today to get started.