Tech Talk Q&A About Powder Coating

"It is not unusual for powder coating formulations to have different charging characteristics. These charging characteristics can be affected by particle size, filler materials, pigments, resins, etc. The proper balance between charging and formulation is normally empirically developed. I would look to the triboelectric series to determine if your filler more readily accepts a positive charge when frictionally charged by teflon. This is a necessary step even when using corona guns. All guns have teflon internal parts that can impose a positive charge on some powder formulations. If this is the case, then this tribo charge will reduce the effect of the negative corona charge by the same amount and therefore affect the total charge on the powder particle. In these cases it would be best to use a positive charging corona gun for the application."

"Laser cut parts have an inorganic soil (oxide) that is produced along the cut edge. This oxide can be removed by mechanical means (i.e. wire brush, sanding, blasting, etc.) or chemically (pickling). A "time saver" automatic sanding machine can remove the oxide very effectively, without manual intervention. Chemically etching with phosphoric or citrus acid (i.e. pickling) can remove this oxide from the part. This process can also be done automatically."

"There is no individual quality standard for powder coating Cold Rolled Steel. Most people set the QC standards to match their customer expectations and the end use of the product being coated. For instance, if your product sees outdoor exposure, then you may want to use an ASTM a standard for salt spray and UV resistance.

The fuzzy balls you see are probable lint or dust particles that have contaminated the powder. First check to see if these disappear during the curing of the powder. If not, then sieve all your powder (including the virgin material) using a 100 mesh screen to remove any contamination. If the fuzzy balls persist, then the contaminants are airborne and an isolated and E. V. controlled spray area is recommended."

"You are on the right track to use a hybrid coating. But your application may allow you to use an pure epoxy which will loose gloss and chalk when exposed for prolonged periods to UV light. If this loss of gloss and increased chalking is unimportant when compared to the greater chemical resistance of epoxies, then you should stick with your first choice."

"All the equipment used in the powder coating industry is not made to spray powdered metals. Powdered metals will short the gun's charging system and wear the feed system in a short time. Sorry, but you will have to go to another industry to find equipment to be used with these materials."

"You have mentioned both corrective actions for tapped holes. Masking with plugs or post machining after coating. There are no other alternatives that can be employed on a production basis."

"Powder coatings cannot be easily applied to tractor trailers since the curing process requires the part (in this case a trailer) to be oven baked at 325 degree F for 30 minutes. That may cause irreparable harm to rubber tires, oil seals, brake linings, etc. Further, powder coatings would not be any better in exposing cracks or stress related defects. Spot repair using liquid paints is not uncommon with powder coated products.

Although powder coating can be applied using flame spray equipment, this will not bring you closer to your goal of having a coating that can be easier to inspect."

" There is a full color informational brochure available from the Powder Coating Institute, Alexandria, VA. Call them and they will be happy to fulfill your request."

"There is a technical publication called Powder Coating; The Complete Finisher's Handbook that is available through this web site. Click here for more info."

"The only wood products that have been successfully powder coated have been low moisture content wood products (i.e. MDO, pegboard, etc.) New technologies like UV curable coatings are being developed as we speak. Even these applications are best used on low moisture content wood products. Any wood products that must move or are moisture sensitive, should be tested prior to commitment of capital funds for equipment."

"Powder coating will adhere to paintable grades of galvanized steel. These grades are known by their proprietary names such as "galvannealed steel", or "paint grip steel". Hot dipped galvanized steel will not provide a surface that is able to be powder coated. The powder will adhere to the galvanized steel but often the galvanized coating will fail from the steel substrate. Zinc phosphate is the normal pretreatment used in conjunction with powder coating galvannealed steels."

"The cure temperature of 400 F has only one effect on ductile iron...the release of entrapped gasses. The cast ductile iron does not become brittle since the part is at temperature for a relatively short time (15 to 30 minutes). Furthermore, higher temperatures are required to cause problems with Ductile or any other cast iron."

"You are looking for a thermoplastic powder coating. These coatings will re-melt under heat conditions and are very soft to the touch. They are available in various formulations (PVC, polyethylene, etc.) and should be selected based upon the properties you need."

"There are 78 producers of powder coating materials in North America. But not all of them have UV curable materials. The Powder Coating Institute (703) 684-1771 has a current listing of their members who formulate powder coatings."

"You have listed all the materials that apply (except for acrylics which are very UV stable but have lower chemical resistance than pure epoxy). Most people select a powder coating that best meets all their requirements with the least tradeoffs. However, some tradeoffs are unavoidable. In your case UV exposure vs. chemical resistance. Select the coating that has the most important feature you need. Often we can't get all that we want in one coating. It is then that a two coat process can be helpful. In this case a chemical resistant base coat with a UV resistant top coat. That may be your best solution."

"In our industry a good pretreament system will provide a surface that is "water break free". This means water will sheet from the surface and not bead or form in droplets. If that is your desired effect, then I suggest that you investigate any pretreatment chemical supplier and ask for a cleaner chemistry that is compatible to your substrate and soil load."

"Surface texture consistency is a direct result of consistent film thickness. I see no reason that a consistent texture can't be applied to the part you describe. Be sure to control your film thickness to ensure a consistent texture."

"Applying an uncured powder coating should work for this job. The spray apparatus costs approximately $4000.00 and must be used in a ventilated spray booth ($10,000 depending upon size) for safety reasons. The uncured powder can be wiped or blown-off with compressed air after you have done your imaging. The spray booth would be helpful in supporting the blow-off operation. Airborne powder can be combustible in the right concentration, necessitating an approved spray booth for safety."

"There are many low cure temp. (250 degrees F) powders currently on the market. Determining which one will meet your specific requirements is a little more difficult. To determine which one will work for you we need your actual performance and appearance requirements. Then we can write a formal specification to solicit quotations from the various powder material formulators."

"No there isn't. Since most powder coatings are considered non-hazardous materials they are normally disposed of as "landfill" materials in accordance with local ordinances. This may mean that your carting company may require you to melt the powder first to create a solid block. Check with your disposal company for pertinent information."

"Contact the Powder Coating Institute (703) 684-1771 and ask for their Custom Coaters Directory. It provides member companies by state who provide powder coating services."

"Plastics are prepared for electrostatic coating in two ways. One is to apply a conductive primer to the surface (Rans-Prep) and then spray it with the electrostatic gun as normal. The second method is to preheat the nonconductive part to 100 degrees F, of higher if the plastic can take the heat, and then spray the part using the electrostatic gun as normal. The preheating of the part works in two ways; one is thermal attraction, the other is the substrate takes on some conductive properties when it is preheated."

"The best source for site-applied thermoplastic materials is Plastic Flame Coat (PFS). They are located in Texas and sell both the equipment and the materials."

"The particle size of powder coatings can be controlled using sieves. The screen size used in the sieve will allow you to separate powder particles as you require."

"Powder Coating is an organic coating that will never achieve the salt spray resistance of zinc plating, an inorganic material. It’s like comparing paint (powder) to metal (plating). Application costs all favor powder coating, which is much cheaper to purchase and apply. Further, powder coatings do not have any environmental problems, normally associated with plating. This further reduces the overall cost of applying powder coatings. It comes down to price vs. performance…plating costs more but provides better corrosion resistance than powder coating. Powder coating can achieve salt spray resistance of up to 1000 hours over galvanized substrates and 500 hours over mild steel."

"There are both hot and cold immersion stripping systems available for this process. Hot strippers can use chemicals, sand, or salts. The hot strippers will not anneal the aluminum like burn-off ovens. Cold strippers use only chemicals. If chemicals are used, be sure to follow all the instructions, take the appropriate safety precautions, and dispose of them properly."

"The galvanneal process releases the entrapped gasses. Most likely the zinc layer is the origin of the gasses since steel substrates do not exhibit similar problems. The bubble density is proportional to the amount of gas entrapped in the zinc surface; more importantly the distribution of surface defects is also related to the physical characteristics of the paint; i.e., viscosity."

"We recommend you use this vacuum method only as a last resort. It would be difficult to implement and would most likely disturb some of the powder and drop it onto the parts below. Look to correct the problem using the following methodology:

1.Locate your load bars outside of the booth (i.e. above the conveyor slot) Use a "Top of rail to top of part distance" of at least 36 inches.
2.Improve the ground on the part to ensure that it is the most appealing target for the powder being sprayed.
3.Remove sources of air currents that may be allowing the powder to migrate onto the load bars, if they are already located outside the booth."

"There are many "flat" or "matte" powder coatings that have low gloss and good mechanical characteristics. In fact, the two are not related. Locate any of the 75 formulators of powder coatings in the North American market who have overseas manufacturing and sales outlets. A list of companies can be provided by the Powder Coating Institute, located in Alexandria, VA."

"Pinholes are sometimes caused by outgassing in unusually thick powder coatings. Since you are fluid bed dipping these parts, I would venture to say that this is your problem. Corrective action can be as follows:

1. Tighter control of film thickness during the coating process.
2. Modification in powder formulation to increase the flow time. This will allow the outgassing to occur while the powder is still soft enough to flow over the pinholes prior to full cure."

"It sounds as though the applied film thickness is varying widely. Employ a more controllable spraying technique for better results."

"The cost to make powder coatings is price prohibited for most end users. Powders are not "mixed" like paint in a hardware store. Powder coatings are formulated by polymer chemists. The formula components are weighed and placed into dry blenders, then extruded (melt mixed), then chill-rolled, then flaked, then ground, then classified for size, and then packaged. This process is not easily performed and can have problems with consistency from batch to batch. We suggest that you purchase your powder from any of the 75 formulators in the USA."

"Powder is normally disposed as non-hazardous landfill waste. The industry has not yet addressed recycling this material, since it is so easy to dispose. I know that the recycle subject is on a the agenda, but it is not going to be addressed by our industry until disposal problems become more acute."

"Powder coated products are readily touched-up in the field. The specific paint to use should be recommended by your powder formulator who will select one that is compatible to the powder coating used."

"Adhesion problems exist for two primary reasons; one is cleanliness of the surface prior to powder coating. Two is proper cure. If the part is not clean after the zinc plating or the powder is under cured after powder coating, then the film will not adhere properly to the substrate. People powder coat over zinc plated parts all the time, therefore, the problem is not related to the zinc, chrome, or the powder.

The solution is to properly handle the parts after zinc plating to reduce soils (hand prints, etc.) and/or fully clean the parts prior to powder coating them. Secondarily, all parts must be fully cured to adhere the substrate. I can’t tell you if these "recent" efforts make sense without seeing the parts. There is an ASTM test method that will check adhesion after the coating has been cured. Prior to powder coating the only thing you can check is the surface cleanliness (water break free & white towel testing)."

"You are looking for a themoplastic powder coating. These coatings will remelt under heat conditions and are very soft to the touch. They are available in various formulations (PVC, polyethylene, etc.) and should be selected based upon the properties you need."

"Most powder coatings can be applied using standard electrostatic spray techniques up to 10 mils. At that point the powder coating will be "self limiting" because the part ground is no longer sensed by the charged powder particles. Preheating the part has been an effective way to overcome this problem in high film build applications.

The sheets can be recoated without stripping the previous coats if some precautions are taken. First the surface must be clean. Second the part must be adequately grounded (less than one megohm resistance). Finally the total number of coats cannot exceed two if the part is fully cured between coats without risking coating degradation from overbaking.

The problems you are having with the holes is called edge coverage. This coating characteristic is formulated into the powder coating and controls the flow and build of the powder on all edges. This combined with the Faraday problem in 5/16" diameter holes will prevent full coverage in this critical area. I suggest that you check the coating spec sheet to ensure that the coating has the edge coverage characteristics you need and preheat the part prior to coating to overcome the Faraday problems."

"There are no published profit margins for the powder coating industry. The adage of "charge what the market can bear" does apply to our industry as with any other industry. Good luck in selecting a price that your customer is willing to pay for the services that you provide. Most job shops are including other value-added services, such as assembly and packaging, to provide a one stop service approach to their customers. This ensures they are not readily shopped by other custom coaters competing for the same business. A rolled-up cost including other value added services can offer you some protection from a commodity marketplace."

"Some of our clients apply a powder coating to stainless steel products. They do not expect the powder coating to provide any mechanical or corrosion properties since the stainless steel performs well enough for their application. The sole purpose of the powder coating is to camouflage the part to better blend into the surrounding environment. For instance green for suburban locations and gray for city locations. You should decide what the powder coating is going to achieve on your product. A barrier coat doesn’t make sense since the stainless steel will perform well uncoated. If you want to camouflage your part, choose a coating that will meet that objective, either powder or liquid. Pretreatment of the substrate is very important for stainless steel. Choose Silane, or other adhesion promoter, to be applied prior to powder coating or you powder will not adhere to the stainless steel. Sometimes, grit basting can perform the same function."

"We have first hand experience with trailer hitch coating since we have a high profile client who is in that business. The failure you are experiencing is very common on that product. The reasons for it are poor pretreatment of the part prior to powder coating. The manufacturer uses hot rolled steels and does not treat these substrates or the weld areas properly prior to coating the part. That means there are inorganic soils on the surface that cause loss of adhesion and corrosion problems with the powder coating. Anyhow, the best fix for your situation is to have the dealer sandblast the hitch down to bear "white metal" and powder coat the part again. This will remove all inorganic soils and defective coatings. Using an iron phoshate pretreatment would also help provide for a better job. The powder coating (a TGIC Polyester is best for this application) will provide a superior finish to any liquid coating, giving you a hitch that will outlast the vehicle."

"There are no major distinctions for suppliers in low temperature applications over normal powder coating application equipment and materials."

"There are no markers that will survive the coating and curing process. Tags work best. But if you don’t want to use them, you can try stamping the numbers into the part itself. Maybe if you tell me why you need to identify these parts, I can be more helpful."

"It is not unusual for TDS to rise in washer tanks. This value represents the "Total Dissolved Solids" within a tank solution. These solids are in your water when you first charge your tank and they are added when they are removed from the parts that are cleaned by the system. This is expected and normal. When you achieve your limit on TDS just dump your tank. If dumping becomes to frequent, then consider inline filtration to remove the particulate. By the way, TDS should be checked in your rinse stages. Adjust your overflow rate to compensate for TDS levels in the rinse stages."

"Powder Coatings can be formulated to achieve different surface appearances. There are "Smoothness Standards" available from the Powder Coating Institute (703) 684-1770 that depict smoothness in a range of 1 to 10. Select the smoothness you want and notify your powder supplier. He will formulate an epoxy to meet your finishing requirements. Be prepared to pay more for the coating and have more sag rejects. Smoothness is a function of flow during cure and can cause sagging on heavily coated parts. Consider using a "Coating Specification" to accurately describe all your powder coating properties. We write these specs as a service to our clients. Consider the problems that you can incur without a clearly written specification: Part rejects, high coating costs, unsatisfied customers, equipment downtime, etc. Contact Powder Coating Consultants at (800) 97-POWDER for assistance in this matter."

"Liquid coatings can be applied over powder coatings to provide a two-toned finish. Selection of the powder and liquid must be done with great care to ensure compatibility. Go to a custom coater for help in selecting the right process and coating materials. The Powder Coating Institute has a list of Custom Coaters by State (703) 684-1770."

"Liquid touch-up paint, compatible with the powder formulation, can be applied directly over the powder coated surface. The liquid paint is available in spray cans, pens, and in bulk."

"No there isn't. Since most powder coatings are considered nonhazardous materials they are normally disposed of as "landfill" materials in accordance with local ordinaces. This may mean that your carting company may require you to melt the powder first to create a solid block. Check with your disposal company for pertinent information."

"Powder coatings are mostly organic coatings that provide superior properties to liquid paints. The application of powder coating is common-place. If you need a painted surface, then powder coatings may work for you."

"There are many system houses that can accommodate your request (over 50 companies). Call the Powder Coating Institute or Products Finishing Magazine. Both of these sources have booklets listing companies that sell these systems."

"Since both the paint and plastic are dielectrics, electrostatic charging can be used. However, the results will be dubious since the charges may cancel each other out. This would result in no powder being deposited on the surface. Normally powder coating is applied to grounded conductive products (metal) using electrostatically charged powder particles. Powder coating plastic has been performed in the past using thermal attraction; the plastic part is preheated and powder is sprayed using typical electrostatic techniques. The heat enhances the adhesion of the coating particles on the plastic surface."

"Nylon 11 coatings are available from Dupont, Thermoclad, Rilsan, and Alf Autochem."

"All hangers must conduct earth ground for the electrostatic attraction of the powder spray activity to work correctly and safely. Therefore, at least the hanger contact points at the conveyor and at the parts must be conductive to ground. These are areas where the build-up of powder must be cleaned. Non conductive hangers will not work in this process and pose a serious safety risk."

"Powder coatings have been successfully applied to glass bottles and decorative pieces (vases, containers, etc.). No one to my knowledge has tried to powder coat toilets. In may be because the powder finish would not be as good as the original porcelain coating. Many toilet manufactures provide their products in lots of different color finishes that are more durable than powder coating. If you want to try coating toilets, preheat the item to gain thermal attraction of the powder. Then cure them as normal. Good luck."

"H. B. Fuller has a complete line of organic powder coatings that can withstand 1000 degree F temperatures. The silver coating you are describing doesn’t ring a bell. This coating may have a metalic base and/or may not be a powder."

"Sounds like you have a surface contamination problem that wasn’t addressed by the window manufacturer. As long as this contaminant remains on the window surface, no paint (powder or liquid) will stick. Clean this area using a solvent and scuff the surface with sandpaper to expose bright new metal. Topcoat with a urethane liquid paint and hope for the best. The window manufacturer should provide some insight as to which paint they recommend for field repairs."

"Many powder coating recovery booths are designed without containment devices and, therefore, eliminate the potential for explosion. These powder booth designs are called Cartridge Booths. On those systems where containment devices are used in the recovery system design, explosion vents will release the energy quickly without damage to the surrounding area. All powder coating systems that employ the use of automatic guns must be protected by fire detection systems that must interrupt the booth exhaust and spray operation within 0.5 seconds of ignition. Those systems with contained recovery systems must also have a segregation damper in the ductwork that is activated by the fire detection system preventing the fire from entering the containment device. Since organic powder coatings do not support flame unless they are airborne within specific limits, their safety record is unsurpassed in the finishing field.

Suppression systems are used if the normal design precautions are not used. This is rarely the case since the cost of suppression systems is quite expensive. If a suppression system is used, it can be activated by sensing thermal, optical, or pressure conditions."

"Without a doubt, yes! The "bring-up" time; that is, the time required to raise the metal's temperature to the cure temperature, is dependent upon the specific heat capacity of the metal and the part's mass. For example, the heavier the part, the longer the "bring-up" time. All powder coatings specify their cure times at metal temperature. Note: these specified cure times do not include the bring-up time."

"Your problem is two-fold; one mechanical, one chemical. First, there is the difference in mass between the two coatings and the effect on thermal attraction. For instance, the liquid epoxy/polyurethane is 1/8 inch thick in an area where the polyester powder coating is probably 0.002 inches thick. Beyond the two different rates of expansion because of the two different materials, the mass difference will allow one material to expand faster/slower than the other. This is a design problem. You have to choose two materials that will expand or contract at the same rate.

The second problem is the chemical intercoat adhesion between the two materials. Your powder formulator can help by adjusting the formulation of the polyester powder coating to more readily accept the epoxy/polyurethane.

"Binders" or primers will not solve your problem and will most likely cause problems with the color of the base coat and the clarity of the clear coat. The process you describe has been successfully implemented by many manufacturers using a base coat powder with clear top coat powder on aluminum."

"No, we haven't. It would seem that the finish would be damaged since the applied powder coating requires some time (approx. 15 minutes) to cure at approximately 400 degrees F. If the product is tumbled during this time the finish would be damaged."

"Standard daily tests for pretreatment are called titrations. Titration procedures are dependent upon the actual chemistry used in the cleaning system. Since each pretreatment chemistry is proprietary, all titration procedures are unique and are developed by the pretreatment chemical supplier.

Frequency of the titration checks depends upon product throughput, product quality, and soil load. When checking to ensure that solutions are within controls, the rule of thumb is that no intervention (adjustment of chemicals) should be required for two out of three checks.

The other powder coating system checks depend upon many things. For instance the type of equipment, the quality requirements, customer specifications, etc. Things, like oven temperatures, powder output, booth performance, powder usage, etc. can be helpful in ensuring that the system is operating properly and doesn't require maintenance.

The Powder Coating Handbook describes test procedures used to verify product quality. Furthermore, we have written many articles dedicated to this topic. We have also assisted many clients in determining what testing should be performed on their products. For further info, contact us for help or buy the Powder Coating Handbook as described in our reference section."

" We recommend using a thermoplastic coating like Nylon or polyethylene. These are functional materials that are normally used to coat the insides of tanks. If you must use a thermoset coating material then look closely at epoxy. It has the best chemical resistance and its low UV tolerance is of no consequence inside a tank."

"The EPA establishes national limits for discharge. These may differ dramatically from your local PTOW authority. You must check with them for your actual limits of wastewater discharge. Contact your local DEP for local air and water discharge limits.

OSHA requirements are usually covered by the MSDS information for precautions on handling the chemicals. We recommend contacting your local OSHA agent for particulars."

"Standard fillers (i.e. Bondo, etc.) will not work under powder coating, since they will outgas during cure of the powder. I do not know of any metal based fillers available on the market that will give you what you want. There are some fillers that have metal in them, but they still have resins and hardeners that can outgas."

"The powder coating material you seek is referred to as an anti-outgassing formulation. This material will stay in a liquid state for a longer period of time when compared to standard powder coatings. During this liquid state, the part is allowed to outgas through the powder coating and then harden as the coating approaches final cure strength.

This material is more prone to sags (runs) since it stays softer for longer periods of time. Whether or not all your moisture escapes through the coating while the powder is in its liquid state can be proven by test."

"Electrostatic fluidized beds are available from Nordson Corporation, Amherst Ohio. They are the only company who currently sells this technology.

Building your own won't necessarily save you much money and if not done correctly, they can be very dangerous. Just think of it, you'll have to build an electrostatic generator, electrode, fluidizing hopper, product transport system, and containment exhaust system.

We strongly recommend that you purchase a system that meets all the codes and is inherently safe against fire and explosion."

"An epoxy powder coating would be the ideal paint for your application. A zinc-rich epoxy primer coating would be even better. Two coats would be better but the top coat should be polyester for its UV stability (of which epoxy has none). UV stability would resist chalking on sunlight exposed surfaces.

You will have to completely disassemble the entire lower unit of the outboard motor before powder coating. Cure temperatures of 350 to 400 degrees F will cook all bearings, seals, o-rings, etc. For this reason, powder coating your outboard motor would not be my first choice.

Some manufacturers looked at powder coating for their in-plant paint systems, but decided to go another way. Using a recommended liquid paint from the manufacturer may be the easiest. Let's face it you are in a fresh water environment which is not as bad as saltwater. Powder coating may just be too much hassle for the slightly improved benefits.

By the way, after you disassemble the outboard, every part needs to be scrupulously cleaned and neutralized using distilled water. Aluminum substrates require a chromic conversion coating (alodine) if you want the best corrosion performance. This type of finish is used by the outdoor furniture market where 20 year warrantees are the norm."

"Powder coating is not better than anodizing. They are completely different. Powder coating is an organic finish while anodizing is inorganic. Anodizing would be harder, more corrosion resistant, more durable, and would last longer than powder coating. It's like comparing plastic to metal; no contest.

Your argument to the city should revolve around: "Better color selection, less cost, opaque vs. translucent coating, and more environmentally friendly". Leave "better" out of the discussion."

"To our knowledge powder coating has absolutely no effect on heat treated aluminum. The cure temperatures are usually under 400 degrees F (typically 325 to 375 degrees F) and should not anneal the 6061 T-6 material.

Furthermore, exposure time at these temperatures is 10 to 25 minutes. The higher the temperature the lower the exposure time to cure the power coating."

"All powder coatings should be purchased using performance specifications to ensure consistency of the coatings from batch to batch. Furthermore, powder coatings are formulated to achieve stated appearance, mechanical, corrosion, and environmental properties. If you don't state your expectations and your system's operational parameters, how would the powder coating formulator know what to deliver to you?

This is why you need a specification to reliably order your powder coating. You can contact us for help in writing such a specification that will ensure proper and consistent performance of the powder coating on your product."

"A clear powder coating can achieve a 2-3H pencil hardness and have great abrasion resistance. These features are important to your specific application. However, this doesn't mean that powder coatings will be impervious to scratching caused by dirt and sand trapped on footwear.

The best way to look at this application is to compare powder coatings to other acceptable finishes. Powder will be superior to liquid paints but not as good as anodizing or plating. You can get clear anodizing on aluminum but you can't get clear plating for steel. If your alternatives for powder are liquid paints, then powder coatings will give you better performance.

However, if your alternative is clear anodizing on aluminum, then powder coatings won't give you the same performance."

"It sounds like the painter screwed up. Powder coatings are formulated to provide a variety of properties, in most cases much superior to liquid finishes. However, if the part was not cleaned properly before coating or the part was not fully cured after coating, then these properties will be compromised. Your vendor should evaluate the part and the resultant damage to assess if the properties that are inherent in the formulation he used are realized. If not, he should strip the part and re-coat it.

If he feels that the properties have been realized, then he chose the wrong formulation (nothing to do with color)."

"There are two ways to powder coat SMC (Sheet Molded Compounds). One is in-mold coating when the part is made. The other is coating the part on a traditional system after it is made.

We have participated in projects that used both methods. If you are not the actual manufacturer of the parts then you would be interested in the second method. SMC products are cleaned and dried prior to being heated to approx. 250 degrees F. They are then sprayed with the choice of powder coating and cured using high intensity IR. It helps if the powder coating is low-cure."

"Yes, powder coatings of all varieties have been successfully used in jewelry applications."

"It is certainly possible that the zinc primer is leaching through the powder coated surface, especially if there were pinholes in the powder coating caused by outgassing. This "white rust" is unsightly and may reduce the life of the product, although it is difficult to determine how much the life will be reduced. If you must eliminate this problem entirely, then you must strip all the coating and zinc from the surface and try again, using an alternate zinc preparation."

"First, you must understand that the powder coating process has to provide a finish that is commensurate with your customers' expectations since the process can be tailored to meet a wide variety of finishing requirements. For this reason there are no "standard" pretreatments used in processing aluminum.

For instance, aluminum pretreatment systems can provide between 1000 - 5000 hours of salt spray and humidity protection. If you make fasteners that are used in the outdoor furniture industry, then the 5000 hour salt/humidity protection pretreatment system would apply. However, if you are making fasteners used in electronic cabinets, then 1000 hours of salt spray and humidity protection may be more applicable.

The costs for procuring, operating, and maintaining these two different pretreatment processes vary greatly between them. It would not be prudent or cost effective to implement a pretreatment process that does not satisfy your customers' expectations or would be excessive for the application. For us to provide a more specific answer, we would have to review your objectives firsthand."

"Since the parts need to bake out at 305+ degrees, there is no way of performing powder coating in the field . There is a "flame coater" that sprays molten powder towards a surface, but this is used with thermoplastic coatings (i.e. PVC, Nylon, Polyethylene, etc.). An appropriate liquid touch-up paint can be used, but this material must be compatible with the powder coating basecoat. Check with your powder material supplier or the painter for an appropriate liquid touch-up material. You may want to scuff the surface before applying the liquid touch-up paint."

"You must remove all the rust prior to powder coating. Approved methods are: grit blasting, wire brushing, grinding, or sanding. Use the method that will provide you the surface texture you can live with. After removing the rust, pretreat and powder coat the parts as you normally would."

"Your assessment of laser scale as the problem is correct. The use of oxygen gas during the laser cutting process will produce a scale (inorganic soil) along the edge of the cut. This soil will be an impediment to proper adhesion of the powder coating. To remove this soil you have three choices:

1. Change the cutting gas to nitrogen to eliminate the soil, but this will slow the cutting speed by two thirds.

2. Mechanically remove the soil using wire brushing, sanding, grinding, or grit blasting. Sanding can be performed in a "Time-Saver" machine with little effort.

3. Chemically remove the soil using an acid-etch chemical process called "pickling"."

"Currently (10/00), the EPA does not consider e-cap a VOC."

"Yes powder coating would dramatically improve your corrosion resistance and is well suited for your application. The automotive industry currently powdercoats a variety of products used in vehicle undercarriages.

Your part size and weight can easily be accommodated in a well designed powder coating process. We suggest you contact us for insight on how best to proceed with your investigation."

"Most powder coaters fuse their waste powder before disposing it. This process should be performed with caution. Always use a metal container (cardboard can catch fire) and do not try to fuse too much at any one time (one drum at a time).

By filling a drum with powder and placing it in a convection cure oven, the powder will fuse and melt down to approximately 15% to 25% of the original volume. You can then refill the drum with more powder and continue the process of melting until the drum is filled.

Since the weight of the powder isn't reduced (just the volume), the weight of the filled drum of fused powder will be quite heavy (approximately 4 times heavier). This method will allow your powder coater to reduce the volume of waste to less than 25% of the volume they currently dispose (i.e. less drums). Furthermore, the landfill will appreciate not having to deal with unfused waste powder, which can be quite messy."

"Loss of adhesion can happen as a result of several process issues. First, is the part clean? A five stage washer should clean most organic soils from the part if it is properly maintained. However, if you have inorganic soils on the part or the process is out of control, then the washer (no matter how many stages) is not doing the job.

Second, is the powder out of date or too old? As powder coatings reach their maximum shelf life (approximately 6 months) then the powder's properties can start to fail and result in loss of adhesion.

Thirdly, is the part fully cured? Performing a solvent cure test in accordance with PCI Test Procedure #8 should tell you if the part is fully cured. Uncured powder coatings can easily fail adhesion tests. The vendor's cure oven may not be operating properly, so just slowing the line speed down will not correct the problem. An oven profile should be performed on your part in a fully loaded oven to ensure that the part's metal temperature reaches the temperature specified by the powder supplier for the prescribed amount of time (dwell time or cure time)."

"No. Changing the gas to compressed air will not prevent the inorganic soil from forming on the metal surface since the compressed air will still have oxygen. If you want to stay with your existing process, then you must remove this soil before powder coating or painting. The recommended methods of removal are grit blast, sanding, wire brushing, or chemical etch (acid pickling)."

"Cyclone efficiency is most effected by the powder particles' velocity and size. If your filters let more air pass through them because they are coarser, then the fan will pull more air volume through the system and the particulate velocity will go up. As the powder particle enters the cyclone at a higher velocity, the cyclonic action will have less influence allowing the powder to go directly into the scrap module. As you use more reclaim materials the particle sizes change (usually coarser). This would normally help the cyclone efficiency."

"For the record, my name is Nick Liberto and I'm president of Powder Coating Consultants."

"When I wrote that article, I was referring to custom designed water quenching equipment. Most system houses in our industry will be happy to quote you one. This method is certainly faster than forced air cool-down, but has some associated risks. For instance, water spots are a problem. However, these can be dealt with by treating the cooling water prior to spraying. There are sheeting agents, softeners, etc. that can be employed to correct this problem.

As far as the proper part temperature for powder coating, your powder supplier is correct in stating that the temperature should be between 125-130 degrees F. Hotter parts will tend to have higher film builds and may begin melting (or sintering) the powder as it is applied. Both of these issues can affect appearance and fit of the coated part. But if they don't, then have at it. Good luck!"

"We can help you determine your equipment needs and floor space requirements. We do NOT sell equipment, but can provide objective help. Otherwise you are on your own. We charge $750.00 per day for this service and it probably wouldn't take more than 2 to 5 days of our help. Call us at (800) 97-POWDER."

"Rinse water quality directly affects corrosion resistance in several ways. First, polluted rinse water will not sufficiently remove the soils or active chemistry from the previous working stage. If the product isn't full cleaned and neutralized, then the next working stage (i.e. iron phosphate, zinc phosphate, alodine, etc.) will not deposit evenly or in the correct amounts to prevent corrosion in the field.

For instance alkaline wash solutions normally precede acidic iron phosphate stages. If the rinse doesn't remove all the soils or neutralizes the surface, the pH of the iron phosphate will be difficult to control leading to poorly formed phosphate coverage. Secondly, rinse water in the final stage must passivate the surface to provide maximum corrosion resistance. This is performed with a slightly acidulated rinse solution (sometime called a sealer rinse). Lastly, all rinse water must be free of chlorides and other contaminants (i.e. CaCo, and salts). If your city or well water isn't up to par, then you will have contaminates (salts) under the coating that will eventually mix with moisture and lift the coating (blisters). This is the normal failure mechanism seen in corrosion failure and is the reason to buy a DI or RO water system for the final rinse."

"Some powder suppliers use RAL numbers to describe their powder coating colors. Check with your suppliers to see if they support this technical standard for color identification."

"Some powders have more by-products of cure than others, often resulting in smoke in the cure oven. You should check with your coating supplier to see if there are any by-products that you should be concerned with. If not, just proceed as normal.

There is a great book on powder coating: "Powder Coating - The Complete Finisher's Handbook". Click here for more info."

"Isocyanurates are not normally transmitted by way of skin contact. Inhalation is the only concern. However, if your painters have sensitive skin they can protect themselves by using conductive gloves supplied by the electrostatic gun supplier or grounded wrist/ankle straps."

"The shape is not as important as the size distribution of the powder particles. Think of applying powder coating like building a stone wall. Smaller stones fill the gaps between the larger stones, leaving a smooth top surface to the wall."

"Fire suppression systems are normally required by your Fire Marshall authority and your insurance company. However, OSHA can suggest safety equipment also. A liquid paint system can have two sets of sprinklers (in booth and after the filters). However, powder coating systems normally have sprinklers in the booth only. The guidelines listed in NFPA #33 (National Fire Protection Association) are the recommendations employed by most governing agencies. However, local authorities can stipulate anything they want.

NFPA #33 states that the "spray area" must have an approved fire suppression system consisting of dry chemical, water sprinkler, etc. The "spray area" has often been interpreted to mean the spray booth, although the room containing the spray booth has also been considered the "spray area". You must comply with your local authority. Finally, sprinklers will not hurt the operator or the equipment. If they go off, you may have to buy new filters for the booth. "

"We know of no powder coating that meets your chemical resistance requirements. There are powder coatings that meet mil specs. The mil spec that comes to mind is MIL-C-24712A and Mil-C-24712A AMENDMENT 1. "

"Electrostatic spray grade Nylon is normally ground to a particle size distribution of 20 to 40 microns. Larger particles are OK, but smaller particles are more difficult to pump and charge. Your customer may have to use a positive polarity corona charging powder gun. This is important since 99% of all powder coating guns are negative polarity. Past experience has proven that Nylon accepts a positive charge more readily. "

"If these crack are truly "hairline" cracks and the powder coating has some excellent flexibility properties, then the coating should hide them. However, coating thickness and surface smoothness will play a role in how well these cracks are hidden. "

"E-cap has recently been removed form the HAPS list and therefore is no longer a concern for powder coaters."

"We know of no such correlation between impact and torque testing requirements. Although the forces of torque are similar to impact, there are several other powder coating functional properties that can be similar to torque. For instance, surface hardness (rated in pencil hardness), adhesion, abrasion resistance, mar resistance, and others can all have an effect on the coated surface when a fastener is torqued to a known standard."

"Any industrial use of property can be subject to pollution. There is nothing specific to powder coating that can cause pollution, but some of the cleaning chemistries may have been disposed of improperly. You should have the site tested by an approved agency. "

"Changing the shielding gas will eliminate the oxide problem, but will slow your cutting speed by almost 50%. All the mechanical methods you mentioned will remove this oxide from your laser cuts. There are chemical methods available to remove this inorganic soil. Pickling is the term used to describe this chemical methodology that uses phosphoric acid or citric acid chemistries. The pickling process can be performed by either immersion (dip tank) or spray wash methods."

"The problem you are experiencing is caused by a scale left by the laser cutting system. Changing the shield gas can eliminate this problem, but will cause the laser to cut at 50% normal speed. You can remove this oxide using abrasion techniques (sanding, wire brushing, grinding, etc.) or using chemicals (pickling). You must remove this oxide to prevent the adhesion problems on laser cut edges.

A normal iron phosphate pretreatment system will not remove this laser scale! Pickling is the only chemical process that will remove this laser scale."

"Yes, several companies are applying clear powder coatings over color powder coatings. The result is a high definition deep coating (high DOI). In fact, many outdoor furniture manufacturers do this on their specialty colors. The process is straight forward (base coat applied and partially cured then the clear coat is applied and fully cured). The base coat will accept the overbake of the clear coat without problem. "

"Powder coatings on MDF is purported to be as durable as laminates. These materials have been used on a variety of products including office furniture. This technology has been around since the late 1990's and does not yet have the track record of laminates. Therefore, actual life testing of these powder materials on MDF products has been limited to the laboratory. These laboratory tests have been successful. The suppliers of these powder coating materials have high hopes that manufacturers of MDF products (store fixtures, office furniture, etc.) will switch from laminates to powder for all their solid colors. We have not heard of any premature failures of these materials on MDF products to date. Actual product wearability properties are dependent upon the specific powder formulation and are available from the formulator of these materials."

"You can try Lab-Metal� from Alvin Products, Inc. This has been developed for use in powder coating operations and can withstand the heat for curing while providing the ground necessary for the electrostatic deposition of the coating powders."

"We are aware of no company looking for "waste powder". However, there is a company (Surplus Powders) who will buy unused virgin overstocked materials.

As for your second question, adhesives do not stick well to textured powders because the labels normally just hit the points of the texture. Additionally, textured powders often have additives that form the texture and gloss that can prevent a good bond with adhesives. Look into changing the gloss level of the textured materials you use. Lower gloss powders can work better with your adhesives."

"You should try a thermoplastic powder such as PVC. The slip characteristic of this material is poor. If you must use a thermoset powder, I suggest you try a textured material.

It may be unreasonable to stack 25 round tube scaffold frames on top of one another without it falling down. Your customer should be more interested in the mechanical and corrosion properties of the powder formula you provide.

"It sounds as though there could be some process problems at your supplier's manufacturing facility. Powder coated steel products are used in extreme outdoor environments without corrosion problems. For this to occur you need to first select corrosion resistant steels. Next you must clean and pretreat them properly before coating. And finally, you must select and apply a powder coating that has the inherent properties to meet the fielded conditions.

It sounds as though your shelving supplier did not meet at least one of these criteria. Along with writing the answers to the Powder Coating Net's Tech Talk section, we are consultants to the powder coating industry. We are an objective technical resource to many clients who are using or specifying powder coatings. To get more information on our company and services, please go to our web site."

"You should check this problem with PPG to obtain an MSDS sheet. The only component that is "hazardous" which comes to mind is ecaperlactum. This additive to many powder formulations is currently on the EPA HAPS list, although I hear that is about to change. If this is the material that your local inspector is talking about, then be aware it is released in the oven during cure. Therefore, operator exposure shouldn't be a problem, unless your oven isn't properly exhausted. I repeat: CHECK WITH PPG TO ADDRESS THIS PROBLEM. They know their formulation and have the resources to address this situation."

"To my recollection, Ford is only using powder coatings for under hood and under carriage parts. Be that as it may, There are over 65 manufacturers of quality powder coatings in North America. Which specific one visited your company would be impossible to guess. Sorry we can't help you on this one."

"The material is generically called "porous polyethylene". It is sometimes sold under the name of "Glass Rock". I encourage you to purchase this material from the company you bought your equipment from. They know what size and shape is required to fit your hopper. If you are trying to design your own hopper or fluidized bed, there is more to it than buying the membrane."

"Yes. Powder coating has been used on plastics that can withstand at least 250 degrees F. These plastic parts are preheated to at least 225 degrees F to attract the powder coating from electrostatic spray guns. The powder is then cured in an oven at 250 degrees F to provide the desired finish. A "low temperature cure" powder coating is used in this process. Sometimes IR ovens are used to preheat and cure the parts without fully heating the plastic substrate. The newer UV powder technologies are also used on plastic parts. In this case the parts are preheated and coated as previously described. The powder is then melted on the surface to flow the material using either convection or IR ovens (approximately 250 degrees F). Finally the powder is fully cured using UV technologies. Either of these methods can work on plastics or some wood products if they can withstand at least 250 degrees F. "

"Yes. The powder material you are looking for using a dual resin system (epoxy and silicone). As the part is subjected to heat above 450 degrees F for a prolonged period of time the epoxy part of the formulation breaks down and is replaced by the silicone portion of the formulation. This material is used on exhaust systems and outdoor grills and is available in dark colors. This material can be cured using IR energy."

"Coating life is affected by many more things than just coating thickness, especially powder coating life. Coating thickness is recommended by the formulator of the coating and is normally specified in a range (i.e. 2 to 4 mils). This coating thickness range will determine the best situation for all the coating properties to be fully achieved. Thicker and thinner coatings will not perform as well as the ideal range specified for the particular coating you have selected. Coating life is directly affected by the selected coating properties, substrate selection, pretreatment of the substrate, and application process control. You can have the best coating, but if you do not select an appropriate substrate, clean and pretreat that substrate properly, or apply the coating with a process that is out of control, the coating will still fail prematurely. Careful selection of the powder coating, correct cleaning and pretreatment of the substrate, and properly controlling the powder coating process is the only way for you to achieve your desired results."

"Nothing good can happen to a part that has already been cleaned and has not been coated and cured. It is always a good idea to store in-process products before they are cleaned and after the coated parts are cured. Not much can go bad with parts in these two conditions. Once a product has been cleaned but not coated and cured it can become contaminated by airborne dirt, inadvertent hand prints, or even flash-rust or oxidization. There is nothing that will happen to the chemicals on the product after pretreatment if left on the conveyor overnight. Using a staggered shift is the best way to eliminate wait times between the process steps and to ensure that cleaned parts are not left on the conveyor line overnight. This would be preferable to leaving the parts on the conveyor overnight."

"Corrosion under the powder coating will cause the film to peel off the substrate. This corrosion is the direct result of improper cleaning and pretreatment of the raw parts before powder coating. If these casting are made from aluminum, then you will have aluminum oxide and salts on the surface that must be removed prior to coating. The approved method for pretreating powder coated aluminum parts that will be used in high corrosive outdoor environments (i.e. salt air) is as follows:

1. Clean the surface (organic soils) using and alkaline cleaner.

2. Rinse the surface.

3. Remove the inorganic (aluminum oxide) soils using a deoxidizer cleaner.

4. Rinse.

5. Apply a chromate conversion coating (Alodine).

6. Rinse.

In lieu of this aqueous method of pretreatment you can grit blast the surface to a white metal profile to remove all organic and inorganic soils before applying the powder coating. However, this methodology will not provide enhanced corrosion resistance as the Alodine system described above. "

"No it is not normal. Gassing can be caused by numerous things, but I suspect that improper cleaning caused it here. The specks can be dirt or other powders that may have been left in the gun or feed system causing cross-contamination. Go get your money back!"

"Zinc die castings are notorious for out-gassing when subjected to the temperatures required to cure powder coatings. The amount of out-gassing depends upon the metallurgical composition, casting vents, chill locations, speed of "pour", etc.

Sometimes preheating the part can reduce the problem, but not always. Out-gassing primers are becoming popular to reduce this problem. You have tried both of these approaches with some success.

Next you should ask your powder supplier for an out-gassing topcoat powder formula. During cure, these materials stay in the liquid state for a prolonged period of time. This allows any gas to escape. The escaping gas breaches the coating and forms holes. However because the coating has been formulated to stay in a liquid phase longer, the coating flows back over these holes to provide a smooth surface.

If the casting has a large amount of entrapped gasses, then this approach will provide limited benefits if all the gas has not fully escaped because eventually the coating will have to gel. It may be that you will not ever entirely eliminate this problem, however using all the recommended methods may reduce your defect rates to acceptable levels"

"Material Safety Data Sheets (MSDS) are available for all powder coatings sold in North America. These sheets describe the hazards associated with a particular coating powder. They will also describe any necessary safety precautions that should be taken while working with the pertinent coating powder. For each coating powder that you may come in contact with, read its MSDS and follow the precautions contained therein to protect yourself from any health risks."

"Most powder coatings do not run (or sag) easily. This doesn't mean they can't run. If they run the coating thickness is above 25 mils (0.025 inches). That's a pretty thick coating. However, liquid paint can run fairly easily even at a thickness that is under 2 mils (0.002 inches). Therefore, you should check the paint thickness and surface appearance (since most powder coatings applied in thick layers will have more orange peel than liquid coatings). If the coating is relatively smooth and thin, then your paint booth was coated in liquid. If the coating has a lot of orange peel and is thick, then it is probably a poor powder coating.

As for wiping the coating with solvent, this doesn't prove much since some powder coatings can't take that abuse, even if the coating was properly applied. Even the best powder coatings will soften with solvent if they are not fully cured. This is in fact the test used to determine cure (using either MEK or a MEK/Xylene mixture). Bottom line, you need to do more investigation before you accuse your supplier of wrongdoing."

"Most all powder coatings are organic finishes and none "penetrate" the surface of the part being coated. However, they all have great adhesion characteristics if applied to a properly pretreated surface. Contact your material supplier for more information on the recommended pretreatment."

"You should check the back of the paint chips that have fallen from the posts. I'll bet that the paint chips have zinc galvanizing on the back side, proving that the galvanizing failed and took the powder coating with it. Hot dipped galvanizing is a great corrosion resistant material and hot dipping is the easiest way to apply this material. The only problem is the galvanizing delaminates from the steel surface over time. Often the steel is still covered with some galvanizing that is still intact.

If this is the case, just use a liquid paint to cover the exposed galvanizing. To prevent this from occurring in the future you should use a paintable grade of galvanizing (i.e. electroplating). This way the galvanizing will stay intact on the steel surface. The powder coating will then adhere to a solid surface that will not flake off over time. Remember, powder coating, like all paints, is only as good as the surface it is applied to. If that surface is unstable, the coating will not perform."

"Each powder coating formulation offers a different resistance to corrosion. The coating formulator (manufacturer) may be able to tell you what the corrosion resistance is for your particular powder. However, since you are testing this performance using specific chemical agents, the coating formulator may have to perform the same tests with these agents in order to determine the actual performance. It is not unusual to empirically test powders for determining their performance."

"No. A typical automotive body shop booth doesn't have filters that can capture powder particles (overspray). The result will be powder escaping into the surrounding atmosphere and landing on cars in the parking lot. Powder on cars has been known to cure in the hot sun. If this happens, you should expect to be repairing the paint job on all the cars parked in the area around your shop. Pay a few bucks and get an actual powder coating booth. It will be cheaper in the long run when you consider all the car paint jobs you would have to repair."

"Normally 16-gauge steel would be unaffected by the powder coating process. Cure temperatures are under 500 degrees F (usually 300 to 450 degrees F).
Steel deformation would not occur until temperatures reach 1000+ degrees F. Most likely your parts were hung improperly or mishandled by your custom coater.�Ask them to be more careful in the future."

"Powder coatings are one of the best performing organic coatings in saltwater environments. Their high dense cross linking provides a coating that is almost impervious to the elements.�This is why powder coatings have been the coatings of choice for use on oil drilling platforms, boating gear, and underwater products.�Of course, to obtain the maximum corrosion performance, you should choose a corrosion resistant substrate, prepare it using a corrosion resistant pretreatment, and apply a powder coating with excellent salt spray resistance."

"Don't bother with the clear powder. They are only used to enhance the gloss of the underlying surface and will not improve weatherability. Since gloss is one of the first qualities of finish to degrade as the coating ages, use a good TGIC or acrylic matte black finish."

"We really do not have enough information to make a definitive conclusion. However, if the surface is as clean as you say and has good surface roughness for the coating to bite onto, then the adhesion problem is either caused by too much zinc phosphate or improper powder cure."

"The powder coating formulator that makes this powder coating is Rohm & Haas in Reading PA. They call it the Lamineer product. They may know who they sell to that applies this material in your area. Furthermore, you can check the Powder Coating Institute for a list of member companies that apply powder coatings. These custom coaters are listed by capabilities and geographical location.
Product Finishing Magazinehas a shop finder for more information on job shops that apply powder coatings."

"Water softeners are not the preferred method of improving raw water quality. They use salts that may affect salt spray performance on your parts. The best way for improving raw water is to use either Deionized (DI) water or Reverse Osmosis (RO) filtration. DI is more economical for smaller usage requirements and RO is better for higher usage requirements. Contact us with any other questions."

"You better have a detailed specification written for the person coating this fence product otherwise it may not perform as well as you would like. This specification would detail pretreatment, primers, topcoats, etc. to ensure a 20 year life on steel. A single coat of powder over mild steel without proper pretreatment, primers, etc. may only last one to 5 years.

However, an outdoor durable powder topcoat over the right primer and pretreatment can give you 10 to 20 years, or more life, depending upon the part of the country it is installed. A good pretreatment and a single coat of powder over aluminum can provide 20 years life, easily. I hope that this helps. Oh, by the way, we write these types of specs all the time for our clients."

"I suggest that you contact the Powder Coating Institute in Alexandria, VA. Telephone number is (703) 684-1770. They may have an answer for you on mil-spec and aerospace-spec type powders. Ask them for their membership information brochure, which includes the names of powder coating formulators, each of whom may have approved materials for your use."

"You should expect the powder coating finish to perform much like the coating on your refrigerator, kitchen range, washer & dryer, lawnmower, lawn furniture, etc. All these products are powder coated. Powder coating is a very durable organic (paint) finish. It is not impervious to scratches and nicks, but is damn close. A laminate will wear like your kitchen countertops (as long as you don't have granite countertops). They can be cut and chipped under very arduous conditions, but for all practical purposes are bullet proof."

"If you are comfortable with the look and function of this mixed reclaim powder coating material, then by all means use it. Mixing different powder coating chemistries can have disastrous effects. Often the coating will have "fish eyes", voids, speckled colors, cracks, wrinkles, etc. It will be particularly hard to determine the physical properties of such a mixed coating, especially if the powder chemistries are very different and incompatible. But if it works for you, go for it. As far as cleaning up the reclaim, removing oversized particles, etc., you need to use a sieve. If you are processing this reclaim in batches a batch vibratory sieve from Vorti-Sieve should work fine. If you want to process this reclaim "on the fly" and continuously, then a rotary sieve from Azo or Prater will do the trick. "

"The answer to your question is not related to powder coating. Dark opaque colors absorb heat and light where transparent colors reflect heat. Anodizing will reflect heat energy while a black powder coating will absorb heat. The heat that is absorbed by the coating will be conducted to the base metal, called heat transfer."

"Powder coating is a factory applied finish that employs several steps (wash & pretreat, dry, spray, and bake cure). Electrostatic-field applied finishes use liquid coatings that are either air-dried or two component cured. Functionally, factory-applied powder coatings will outperform most field applied liquid finishes because of the excellent surface preparations and better properties of powder coatings. Powder coatings cannot be applied reliably in the field, especially to a rolling steel door. "

"Depending upon what salts and soils are left on the surface and the rate of temperature rise on the part during curing, the simple answer is yes. Polished brass surfaces have successfully been powder coated after great care has been taken to ensure that the surface is completely clean and neutralized and the curing temperature is gradually induced into the part using convection heating techniques."

"You raise an interesting question, How clean is clean enough for powder coating? Liquid coatings that contain petrochemical solvents can "bite through" light oils left on the part`s surface to provide adequate adhesion. Since powder coatings do not contain any solvent, residual oils left on the part surface can be an impediment to proper adhesion. Furthermore, organic soils (such as oil) can bleed through light colored powder coatings under the high heat conditions experienced during the cure cycle. For these reasons it has always been good practice to scrupulously clean the surface prior to applying any powder coating."

"However, cleaning requirements can be less critical if the powder coated product does not have high quality appearance and adhesion standards. The coating performance depends upon perceived quality requirements and will dictate the appropriate process requirements. This fact is proved in the automotive industry where under carriage parts have a 336 hour salt spray corrosion requirement and the body parts have a 1,000+ hour salt spray requirement. In this case, the automotive companies sense that their customers will accept rust in short order on the car`s suspension springs but not on the car`s fenders. Therefore under carriage parts are pretreated much differently than body parts. Using the same pretreatment for all parts will ensure that either the body parts will not perform up to expectations or the under carriage parts will be too costly to manufacture."

"How clean your motor housings need to be is dependent upon what your customer expects from the powder coated finish. Understanding this requirement is paramount for determining the appropriate finishing process. You have several options to clean your motor parts prior to applying the powder coating:

• Do not clean the motors at all. This may provide an adequate solution since the parts are cleaned and pretreated prior to arriving at your facility. Use clean lint-free gloves to handle the parts prior to powder coating. Remove any loose contaminants such as dust and dirt before coating.
• Use a vapor degreaser to remove any residual soils on the parts prior to powder coating. This method of cleaning has been under scrutiny by the EPA, so be sure you are in compliance with all federal, state, and local statutes.
• You can solvent wipe these parts prior to coating. Be aware that this method is suitable for lightly soiled substrates. Change your wiping rag often to prevent reapplying the oils. OSHA, EPA, and the local Fire Marshall closely watch this method of cleaning, so be sure that you have plenty of ventilation and are in compliance with all other safety and disposal requirements."

"Try a test batch of products to ensure that the chosen method will work consistently in your facility. Check the parts for proper adhesion after they are fully cured. Also, be sure to run any performance tests your customer may require on these motor housings. If the test results are acceptable, then you have a successful powder coating process."

"Your powder coating supplier will have the answer for you. It is important that you tell him/her that you intend to silk screen over the powder, since they must modify the formulation to accommodate this. They may tell you that the powder material that you have selected will not accept a silk screen ink. If it does, then they can tell you which inks are the most appropriate."

"Call the Powder Coating Institute and ask them for their "Custom Coaters Directory" which lists many powder coaters around the country. There is probably a reason there are a limited number of people who provide this service in your area; not enough business to support more custom coating companies. This may influence your decision to open a competing shop.

The cost of starting a powder coating operation, with new equipment, starts at $50,000.00+ for a batch system and can approach $1,000,000.00 for a conveyorized system without much effort. The only difference between these two systems is the amount and size of product it can process in a given period of time. For your reference, a powder coating gun costs approximately $4,500.00 each, spray booths start at $10,000.00 each, and that doesn't include the cure ovens and pretreatment systems that are necessary for this process."

"The problem you are experiencing is the result of poorly charged powder due to a Faraday Cage. The powder that you see in the corner before cure is not fully charged and falls from this surface when subjected to heat. This situation has happened before. This is a difficult problem to solve, since you need lower charge on the powder particles to get it to go into the Faraday Cage and then when these lower charged powder particles are put into the oven they fall from the surface.

Here are three solutions:

1.Use a tribo charging gun to coat this area.
2.Orientate the part so that the Faraday Cage is at the bottom and hope the powder flows into the corner.
3.Contact your powder supplier to obtain a powder coating formula with lower flow characteristics. (less flow) "

"You should review this situation with your powder coating material supplier. They understand the formulation intimately and can recommend the most appropriate action. Having said that, below is some general information:

Clouding in clear powder coatings can be caused by under cure, over cure, contamination in the coating, UV instability of the formulation, improper oven exhaust rates, and improper formulation. The powder supplier can help you determine which problem is causing your clarity problem."

"These stains are indicative of residual oils left on the part prior to powder coating. Posssibly they are bleeding from hidden area, such as at spot-welded joints. In either case, the stained area will probably fail before the other areas of the part. Therefore, if you are looking for consistent quality from part-to-part and within the same part, then you must sand the area and recoat. However, if potential failure of the coating in this area isn't a concern, then try cleaning it with a strong solvent and touch-up with liquid paint. Be aware that these areas will not be as good as the original powder coated surface."

"There are many companies that use powder coating for surgical instruments. They purchase powder and pretreatment chemicals (raw materials) from many companies (68 powder companies in North America alone). Similarly, there are several equipment companies that sell the application equipment employed in this process. To obtain the names of these companies you should contact The Powder Coating Institute in Alexandria, VA (703) 684-1770 and ask for their informational brochure and list of member companies. Unfortunately, it is difficult to determine which of these companies support the medical instrument industry. However, it wouldn't be to difficult for you to determine your unique process requirements and finish performance requirements so that these vendors can sell you an appropriate solution. Contact us if you need help to determine your requirements."

"The five-stage pretreatment sounds ok, depending upon what each stage is doing. Powder is used in all sorts of outdoor applications without UV problems. The only thing that needs to be considered is which powder to use (based upon your customer's performance requirements). Powder coating over chromate conversion coatings on aluminum can provide 5000 hours salt spray resistance and can translate to over 20-year life (in outdoor environments). We can be contacted through this web site or by telephone (800) 97-POWDER."

"E-coat is an appropriate primer for powder top coats. In fact, this is the method preferred by customers looking for the best corrosion protection available with organic coatings. There is only one way to apply an e-coat primer; with an e-coat system. There are a couple of ways to employ the e-coat process (autophoretic, etc.). Check with an e-coat material supplier for the best material and methods for your specific product. PPG is a premier supplier of e-coat materials. Be advised that if you do not have a source for getting this coating applied by an outside contractor, you will be looking at a substantial capital investment (can be $1.0 million). Good luck."

"There are several powder companies that make mold release for the fiberglass industry (referred to as "in-mold coating"). Also, there are many powder companies that make FDA approved powder materials. However, I do not know of any company that makes mold release compounds for the bakery industry.

I am not entirely sure what you are looking for in this application. For instance, if you need a slippery compound to be permanently bonded to these molds(like Teflon), or if you want an edible material to be sprayed onto the mold.

Please feel free to re-ask your question with this additional information."

"BGK is a premier manufacturer of such IR ovens. Their address is:

BGK Finishing Systems, Inc.
4131 Pheasant Ridge Drive NE
Minneapolis, MN 55449
Telephone: (612) 784-0466 "

"TGIC polyester powder coatings are formulated for superior outdoor weatherability and corrosion resistance. To improve salt spray, look to your pretreatment chemistry and/or your substrate materials for alternatives that will provide better salt spray characteristics. Also, look to your process control for improvements on the current materials that you are using."

"There can be many subtle differences between all these coatings, and many features can be formulated into each coating. However, the general functional differences are as follows:

Epoxies are very chemical resistant but have no UV resistance (weathering).
Urethanes have great weathering characteristics but do not have good flexibility in impact resistance.
TGIC Polyesters have good weathering but reduced chemical resistance.

Hybrids is a term that describes a mixture of resin technologies. Depending upon which resins are used, they can have all sorts of properties. One of the most common hybrids is an epoxy-polyester hybrid which has most of the properties of pure epoxy coatings with some added UV resistance (weathering) of polyester coatings.

There are many more features and properties in each of these coatings that you should discuss with the material suppliers."

"Stainless steel is very difficult to coat without adhesion problems. The iron phosphate will do little to prepare this surface for adhesion.

Pretreatment for stainless steel is focused towards adhesion, since corrosion resistance is not a problem with this substrate. You should review your requirements with your chemical supplier and ask for his recommendations.

Changing the substrate to galvannealed steel can provide for better adhesion; however, it will not perform as well with corrosion. Review your performance requirements carefully before you select a substrate material."

"Find out how profitable they are! That is the only question you should ask when purchasing a company."

"Loss of adhesion with powder coating can be caused by any of the following:

1. Poor surface cleaning.
2. Poor surface pretreatment.
3. Under cured coating.
4. Over cured coating.

To know what is causing your particular problem requires some detective work. If there is foreign matter on the under side of the chip, then your problem is in the pretreatment of the product. If the chip is clean, then check your cure. Good luck."

"Used equipment can be found from many sources. There are used equipment dealers that advertise in the trade journals. Also, there are private parties that are selling their old system as used equipment. Look for these in the classified section of the trade journals.

There are no marketing studies for the end user in the powder coating industry for under $2,000.00. The studies that are available are mostly for equipment and powder suppliers and not end users. You will have to do your own market survey for the area that you want to service with your new business."

"Contact the Powder Coating Institute in Alexandria, Virginia, (703) 684-1770. Ask them for their "Information Brochure" which will provide you the names of their member companies that sell powder coating equipment."

"Evidently the powder formulation that you are using does not have good "edge build" characteristics formulated into the coating. You should contact your powder supplier for further explanation."

"Ionized air knifes have been used in many applications where the product being coated has charged contamination adhered to the surface. If this isn't your problem, then you don't need the system. The problem with air knives is they use compressed air, which depending upon the volume, can be very expensive to make, dry, and filter. A system that has gained acceptance in our industry, when compressed air costs are too high, is an ionized blower system. This design uses the same ionized generator, but uses an electric blower to supply the air instead of compressed air. I hope this answers your question."

"You are looking for a high temperature powder coating, of which there are a few on the current market. However, I do not know of any high temperature powder coatings that come in white. You should contact H.B. Fuller, who has the most products in high temperature formulations, to ask them. Good luck."

"The temperature for a powder storage area should be held between 60-80 degrees F. The relative humidity should be less than 60%. As far as codes, you should check with your local fire marshal and building department for the fire rating of the structure and what fire protection/suppression systems are required. Your insurance company should also be asked if they have any special requirements."

"Usually rinsing the substrate can neutralize the surface, if it is grounded during this procedure. There are ionized air blowers and compressed air units that can neutralize the part's surface. Check the Thomas Register under Ionized air systems for manufacturers names."

"This would involve the details of powder coating formulations, which are often carefully guarded by the powder manufacturers. It is not generally a good idea to just mix powders on the fly. You might try contacting the Powder Coating Institute for more information."

"There are several powders that are formulated to cure in under 300 degrees F. Contact the Powder Coating Institute for their membership directory which lists some suppliers."

"Outgassing can be caused by contaminants on the substrate or from the powder itself, if it is applied too thickly. You should definitely contact the manufacturer of the material for some guidance."

"The water quality should be less than 250 ppm of CaCO3 and less than 100 ppm of combined chlorides and sulfates. If your water cannot meet this criteria, you should use demineralized water (either ion exchange or reverse osmosis)."

"Get your money back. There is nothing that I can tell you to fix your problem, since you don't have the process equipment. Bubbles can be caused by contamination on the substrate and/or corrosion after the part has been used for a while. Good luck."

"There are many issues that need to be discussed as part of your conversion to powder. We cannot possibly address them all in this forum. Please contact us at (800) 97-POWDER and we will be very interested in discussing our services with you."

"Since engine blocks are not exposed to sunlight, then UV resistance shouldn’t be a coating requirement. If you agree with this, then I suggest that you investigate using an epoxy powder coating. This material has excellent chemical resistance (oil, gasoline, etc.) and is very durable (chip & mar resistant). Furthermore, epoxies are very inexpensive and can provide an excellent coating in non-sunlight exposed products. If exposed to sunlight (UV light) epoxies will tend to chalk. Chalking will not adversely affect any of the previously mentioned coating properties of this material."

"Many powder formulations have post-forming capabilities. The typical resins used are epoxy and polyester. Although both of these can be formulated for post forming, they have different UV resistance characteristics. This highlights the need for a well defined powder coating material specification that lists ALL your requirements so that your coating selection can achieve these requirements. This will insure that you purchase the powder coating that fits your requirements and not a coating that a salesman wants to sell you.

There aren't any "State of the Art" coatings for a post-forming environment. Powder coatings have been used for years in applications where a zero "T bend" is a requirement."

"There should be no adverse effect if the coating is applied properly at the recommended film thickness. Many people have already gone this way with no problems."

"PVC coatings are thermoplastic resin systems that are almost always "flexible". The powder formulators that manufacture these coatings also have liquid primers that greatly improve adhesion on most substrates (including metal). I hope this helps you in your project. You can call us at (800) 97-POWDER for more information."

"There should be no adhesion problems if the substrate is properly cleaned prior to applying the powder coating. Check with the powder supplier and pretreatment supplier before proceeding.

Life cycle of TGIC polyester over an alodine (chromate conversion coating) is 5000 hours of salt spray. An outdoor furniture supplier, who sells to beachfront resorts guarantees this finish for 20 years. You will have to determine what this means to you with TGIC over anodized aluminum."

"The book that you want is available from the Powder Coating Institute in Alexandria VA. Call them at (703) 684-1770. Ask for the "Powder Coating Handbook" ($75.00 US plus shipping and handling). It's a good book and recommend it to anyone interested in getting more information on powder coating. Nick Liberto of Powder Coating Consultants was the Editor and a contributing author."

"You can call the Powder Coating Institute (703) 684-1770 and ask them to send you their membership directory which lists all the member companies who formulate powder coatings. Contacting these vendors directly will allow you to obtain their color charts and product descriptions for their "stock" materials. You will see that there are a wide selection of colors, textures, wrinkles, gloss values, clears, tints, flamboyants, etc. I'm sure that if you have seen a specific look in paint you can get the same look in powder coating."

"KV's (voltage) will drop as microamps (current) goes up. This is determined by the laws of physics. You are probably bleeding your corona field towards the booth, and definitely to the metal strip you are coating. Therefore, a drop in KV is very likely.

The important thing is to ensure that the KV's are being directed toward the strip and not the booth. Check and adjust the position of the guns to be sure that the primary target is the strip and not the booth. Monitor the current (microamps) during spray and compare them to readings taken without powder spray. They should be higher when spraying. If all else fails, call your equipment supplier."

"The cost for a batch powder coating system of the size that you are considering is as follows:

Gun & Feed system = $5,000.00
Spray booth = $10,000.00
Cure oven = $30,000.00
Pretreatment & Cleaning system = $10,000.00

Total investment = $55,000.00, you could save some money if you can locate some used equipment."

"Most thermoset organic powder coatings will not conduct heat as well as an uncoated part. Therefore, you can assume that all these coatings can be considered thermal barriers to some extent. The most important issue is not which coatings are best for this application, but rather which color and what thickness the coating should be. For instance, black is the most appropriate color for thermal transmission. It shouldn't be applied more than 2.0 mils thick."

"It has been well documented that powder coating has been used in several key areas in the manufacturing of automobiles. For instance, under-hood (oil filters, etc.) and under-carriage (coil springs, etc.) parts have been powder coated for years. Some exterior trim components have also been powder coated. Selected areas of some vehicles have been powder coated for anti-chip protection (rocker panels, etc.). Entire vehicle bodies have been fully primed with powder coating. In the USA market the next growth area for powder coatings in the automotive industry is clear-coating the entire vehicle body. Don't expect to see the color coat of the vehicles to be powder coated in the near future, since the 8 second color change requirement has been difficult to overcome with current technology (we just can't seem to get the previous color out of the booth air stream in that 8 second time frame)."

"There is a software program we developed for the Powder Coating Institute that uses a spreadsheet to compare typical powder coating operational costs to liquid coating costs. This spreadsheet is modeled after the PCI Technical Brief #21 that has been used for years to compare the most obvious operational cost differences. The diskette is free for the asking . This will provide the data that you are asking for in a clear and concise manner."

"The Powder Coating Institute in Alexandria, VA has a government relations committee that deals with military standards and specifications. They can be reached by telephone at (703)684-1770. Good luck!"

"Contact us for information about our rates. We have the expertise you require."

"The best powder coating material to use is epoxy, for its chemical and chip resistance. Be aware that this material is not UV stabilized and will chalk over time if exposed to UV light. If UV stability is required, then I suggest that you use a polyester material, which is stable under UV light conditions and will not chalk, but has some reduced chemical resistance when compared to epoxies.

The procedure that I would use is to sandblast the entire frame and pretreat it with an iron phosphate chemical using a spray wand system. After the frame is completely dry, powder coat it completely with about 2 to 3 mils thickness. The frame must be put into an oven to cure the powder coating for 20 minutes at 375+ degrees F.

Operator techniques are the best way to overcome Faraday areas. I wouldn't worry much about them, since you can always touch-up those areas with liquid paint after the powder has been cured."

"There is no direct analysis between e-coat and powder coating that we're aware of. However, there is a comparison between liquid spray and powder coating implemented as a computerized spreadsheet. This spreadsheet software is available from the Powder Coating Institute (PCI)/ 703-684-1770.

If you use this spreadsheet for e-coat, remember to adjust the coating thickness and the efficiency rating for that technology. We developed this spreadsheet application for PCI and can assist you in your comparison for a fee. If you are interested call us at (800) 97-POWDER."

"Galvanizing can be accomplished in several ways. Depending upon which method is used will effect your outgassing problem. For instance, if the part has been hot or cold dipped galvanized, then trapped gasses are likely. When the product is heated these gases are released and cause holes in the coating. Other methods of galvanizing, such as electroplating or galvanneal products will not outgas at all. To eliminate the outgassing either change to a galvanizing process that will not entrap gasses (i.e. electroplating or galvanneal), or preheat your product to the cure temperature to release the entrapped gases prior to powder coating."

"The first step is to use a paintable grade of galvanized steel (i.e. galvanneal, paintgrip, or electroplated galvanized). Hot or cold dipped galvanized steel will cause problems with out gassing and powder adhesion.

The preferred pretreatment for galvanized steel is zinc phosphate. This will provide prolonged salt spray resistance and excellent adhesion. A chrome sealer rinse would also be nice, if you can use that material in your country. The pretreatment system typically has seven or more stages to apply these chemicals, depending upon the soil load on the raw product. You should contact a competent pretreatment chemical supplier for help in selecting the right chemistries.

The product should be perfectly dry before powder coating. A dry-off oven suits this task well. The part should be cool to touch at time of powder coating. Coat and cure the product as normal with your equipment."

"To powder coat aluminum, you must have a completely clean surface. Normally aluminum has some oxides on the surface that can cause problems with adhesion and corrosion protection after coating the substrate with powder. These soils must be removed for the powder coating to provide maximum protection and excellent clarity through the coating. Fluoride in solution is normally used for this purpose. Review your specific requirements with a knowledgeable pretreatment chemical supplier for further information."

"There is one equipment supplier that sells a laser device to measure uncured powder coating thickness. The device is quite costly, approx. $60,000 +, and can tell you the coating thickness in the exact location where the laser hits the target. No information is provided form any other locations on the coated surface. You would have to have one heck of a gun set-up to ensure that the entire surface is coated with the same thickness as the area measured by the laser. The equipment supplier is Wagner-Reclaim, and they are located in the Chicago area.

One point to remember, is that powder coating thickness shrinks as the coating melts and cures. So the reading may be on the high side when compared with the after cured thickness measurements. This situation may be corrected with the laser equipment through calibration. Check with the supplier for more details."

"Matte or textured finishes are more difficult to formulate and apply than high gloss powder coatings. However, there are over 75 powder formulators that have provided such materials on a consistent basis to many end users. If you are having trouble with your current supplier, then I suggest that you look elsewhere.

Most powder coating formulators are listed with the Powder Coating Institute. Call them at (703) 684-1770 and ask for a membership directory. As in any industry, there are different levels of expertise with the different suppliers. As late, many regional liquid formulators have entered the powder coating formulation business. These new suppliers usually do not have the experience that the more traditional powder suppliers have. Look to deal with a supplier that has at least 5 years of experience in powder formulations."

"Boy it seems that you looked at all the obvious areas of the powder feed system. I would have to assume that the transfer pumps are clean and operating properly, if you are refilling the feed hopper with reclaim powder at regular intervals. If this is not the case, then look at that.

Next, you should make sure that the feed rate is indeed changing or is the transfer efficiency (what ends up on the parts) is changing. The latter suggests that if the output for the guns is the same, then the powder isn't charging properly or the part ground has gone away.

The easiest way to check powder charging is to check the output current of each gun. This is not the voltage reading that you normally check. To read current output, check your manual for instructions. Usually, you push a button or pull the voltage adjust knob, and the current reading is displayed on the voltage meter using a different scale. The current is a measurement of work for the charging mechanism of the gun. You can have voltage present without current. This means that the field exists, but the charge is not transferred to the powder particle. Current readings should read between 20 and 50 microamperes.

If this reading is OK, then check for proper ground on the part to be coated. There should be less than 1 megohm resistance to ground in the entire circuit (part, hanger, conveyor, etc.). If this is resistance is above 1 megohm, then clean the contact points along the entire circuit. Burn-off the hangers, clean the conveyor, etc.

The other area where transfer efficiency can be effected differently each day would be environmental conditions (temperature & humidity). These will effect the rate the powder is pumped and charged. Normal limits for these can be obtained from your powder supplier (65-85 degrees F & 40-60% RH).

If you are still having problems after checking these parameters, get back to us with more information."

"Food seasoning may not react as powder coating does. However, for your information, 60 fpm is the air velocity that will control powder particles. All powder coating spray booths are designed with this value in mind. I'm not sure if the same air velocity will work for your application."

"Pretreatment for metal parts in a powder coating system provides for corrosion resistance and not attraction of the powder. The only thing you need for proper electrostatic attraction is a good ground on the part (less than one megaohm), a properly maintained gun, and some control of the environmental conditions in the spray area (50-60% RH & 60-85 degrees F)."

"The new thin film powder coatings are being developed with variations of two important characteristics. First is flow rate; the ability of a powder coating to flow smoothly at thin builds. Second is particle size; this is a function of the grinding technology. You make a valid point that as film builds get thinner, better pigmentation with better hiding power is important. I'm not sure if the technology has addressed this issue yet. Thin film builds in the North American Market are typically 1 mil. Powder coatings applied under this threshold have not yet been marketed."

"Most powder coatings have ZERO (0) VOC emissions in the cure process. The only emissions that are exhausted from your cure oven are the by-products of combustion from the fuel source. For a while e-cap was on the EPA HAPs list. But even this component has been reclassified and is no longer a HAP. You should verify this with your powder formulator. You may have some different rules for California that don't apply to the rest of the universe."

"Thickness isn't the important an issue as formulation. I suggest that you use an epoxy powder coating at 3.0 mils thickness."

"Before you start buying any equipment, you should first determine exactly what you need by using independent consultants like us. We can help you identify your requirements and then advise you as to which manufacturers can best meet your needs."

"You are doing way too much to work to obtain a 240 hour salt spray corrosion requirement. Galvanized steel, zinc rich primer, and powder top coat would be used for 2000 hours salt spray resistance. I'm afraid that in this case "more is not better". Each process step requires stringent process controls to be done correctly. The more you do to your product the more you risk creating a reject. Statistically, all the possible problems are compounded on your product. You should consider, redesigning your process (simplification) to accommodate your corrosion requirement."

"The problem is "transparent" powders will not hide any defects on the substrate. Therefore, complete removal of this yellow ink is required. Solvent wiping will just dilute the ink an spread it around the surface. An aqueous cleaner with high impingement (mechanical action) can produce the best results. A light sanding with a fine grit paper should follow the cleaning. Contact a pretreatment chemical supplier for an aqueous cleaner (alkaline or acidic)."

"Purchase the Powder Coating Handbook. See Tools & References."

"Powder coating reclaim systems are designed to accommodate a wider range of particle size. There is no single particle size that is best, although finer particles are more difficult to fluidize and pump. Powders are formulated and ground to a bell shaped curve that has a range of particle sizes form 20 to 40 microns. This range accounts for the highest percentage of the particulate. However, there are particles that fall out of this range (less than 10 and greater than 50 microns) but they are few in number. The problems exist in a reclaim system when the bell shaped curve shifts toward finer particles (i.e. 50% or more less than 10 microns). Below 5 microns and the filters have difficulty capturing these particles. Remember, smoke is 15 microns, so what we are describing here is real small stuff.

Powder coating systems need smaller particles to fill the voids between the larger particles. If smaller particles were absent, then your surface appearance will have more orange peel. Imagine building a stone wall with all the same size rocks. If you don't have small ones to fill the gaps, then the wall will have a rough surface.

Virgin powder mixed with reclaim will eliminate all reclaim problems. Most suppliers recommend a mix ratio of at least 50% virgin material. If your first pass transfer efficiency is too low, then this may pose a problem. I suggest you check your transfer efficiency and improve it to at least 50% and don't worry about the reclaim particle size. Particle size is difficult to measure and control anyway."

"Teflon is a registered product name owned by Dupont. They would be the supplier of this material or have a list of authorized Teflon applicators. PTFE (the generic name for Teflon) materials are manufactured by various other powder formulators. Contact the Powder Coating Institute (703) 684-1770 for more information."

"There is no "test rig" available to test fluidization. Fluidization is normally checked visually. The bed should have a simmering pot look to it. Boiling or no movement is unacceptable. There are devices (level probes) to measure the height of the powder within the fluidized bed (or hopper). Contact your equipment manufacturer for more details."

"Due to the lack of an earth ground in the non-conductive wood strand, it would not be appropriate to use electrostatic powder applicators for this process. Powder equipment has been used in a variety of non-finishing applications with some success. But this application probably will not work because of the eight foot drop immediately after application of the material."

"Sieberts has a material that simulates a chrome look. It looks best when applied to wire products (i.e. shelving). On larger surface areas it looks like a glossy gray coating. Sieberts also has a pretty good variety of tinted clears that can look very nice. Good luck in your search; but remember no organic coating (powder) will ever look exactly like an inorganic (plating) coating."

"There is a book that is available from us called "Powder Coating: The Complete Finisher's Handbook". It costs $75.00 US plus shipping and handling. If you buy it from us we can save you some money ($60.00 US + shipping). This book covers the entire powder coating process and will answer all your questions. I am the book's Editor and I am very proud of its contents.

Lettering over powder coating can be a problem if you don't know what powder was used. Compatibility between the powder, the lettering, and clear coat is important for adhesion. Find out what coating was used and contact the local rep from that company for suggestions."

"Powder coatings are cured using infrared technology all the time. Line of sight issues aren't a problem on such a symmetrical surface (cylinders). The cylinder will have to be rotated in front of the IR lamps to heat all surfaces. If you use this technology, the cure time is shortened to as little as thirty seconds. The heat won't penetrate the substrate (heat it through) in this short period of time."

"The material used for this purpose is normally epoxy. However, you should discuss your requirements with a powder coating formulator. There are 75 formulators in the US. I'm not sure how many there are in Germany. For a list of the US suppliers contact the Powder Coating Institute (703) 684-1770."

"All grounding rods are homemade and usually crude. They are used as a last resort to provide a good ground to the parts being sprayed. All efforts to provide the ground through the conveyor and hanger should be made first. Ground rods can cause ungodly noise and dirt (iron filings) within the powder booth.

Clean your hangers and conveyor parts on a regular basis and you won't have to deal with this issue. One megohm (1,000,000 ohms) resistance to a known ground is allowable under NFPA code."

"The Powder Coating Institute and the Chemical Coaters Association both have training materials and video tapes. Contact them directly for more information."

"I would use a high nickel content stainless steel first. A marine grade stainless steel can be very suitable for your situation. If you really want to powder coat this part, use an epoxy powder coating. This powder is the most resistant to salt water corrosion."

"Acrylic powder coatings are very hard materials and provide superior UV stability. Zinc-rich powder coatings can be a very effective primer for TGIC polyesters. However, I would investigate better substrates (Galvanneal) and pretreatment (Zinc phosphate) before using a primer. These (galvanneal & zinc phosphate) in combination can provide up to 1000 hours of salt spray protection on a scribed panel."

"Contact the Powder Coating Institute (703) 684-1770 and ask for their "Custom Coaters Directory" which lists over 50 job-shops ready to provide you their services."

"Prepainted materials offer high quality coverage at a low cost. However, they do not have the same properties of powder coating which can outlast prepainted stock. Additionally, tool life can be reduced with prepainted stock (abrasion and dulling of punches an dies).

Furthermore, the raw edges of prepainted stock after shearing can be a problem on some parts. Prepaint stock has not substantially affected the powder coating market to date and has been around for more than 20 years."

"Cryogenic grinding is sometimes used in the manufacture of low temperature powders. This technology is employed by only a few powder formulators. Who is specifically doing this at this time is hard to say. We suggest that you contact the Powder Coating Institute, Alexandria, VA for more information."

"PTFE powders can be applied by electrostatic spray to substrates at 1.5 mils or greater. PTFE powders usually need a liquid primer for adhesion to the substrate. Knowing these two facts, can it be assumed that a 1.5 mil coating of PTFE material, applied at 1.5 mils without a primer and allowed to flow into a continuous film be removed (peeled) to form a sheet? I don't think so, since the film would probably tear during removal. But it sounds like an interesting experiment to try."

"Sorry, but all custom job shops price their work as any other business. They charge according to their market, competition, cost, etc. You are going to have to determine what price you can charge for your service to remain competitive, and make a profit."

"Powder coating is a manufacturing process whereby an organic coating is applied to a substrate and cured to a durable finish. Parts to be coated are cleaned, pretreated, and dried before coating. The powder coating material, as the name suggests, is in particulate (dust) form. This material is applied by either dip or spray techniques. The parts are cured using heat, resulting in a very durable and high quality finish that resembles liquid paint without the solvent problems. There are several books on the subject. The best one is "Powder Coating; The Complete Finisher's Handbook", which is published by the Powder Coating Institute. Copies are available from them for $75.00 plus shipping and handling. We sell this book at a discount for $60.00 plus shipping and handling."

"The best method for coating these pipes and valve in place is to use a system called "flame spray". The equipment for this process is sold by Plastic Flame Coat in Big Spring, TX. This process has been very effective at applying thermoplastic powder coatings on large objects that require a corrosion barrier. For instance, rail cars, water tanks, bridges, etc. I would suggest that you drain the oxygen from the pipes before you use this process. Contact them for further information."

"Chrome plating can be stripped by an informed plater. Many powder coatings have high gloss characteristics that do not require a clear top coat. However, if you are looking for that deep depth of finish, like the old laquer jobs, a clear coat can offer that look, although with more orange peel."

"The advantages of powder (an organic finish) over plating or galvanizing (an inorganic finish) are all on the application side. Powder coating can be applied without the hazardous waste associated with the plating or galvanizing. However, organic powder coating, although superior to other organic finishes, will not perform as well as inorganic finishes. Knowing this, you should test powder coatings for the specific weathering, and any other performance characteristics, that you require for your product before considering a switch to powder coating.

As for adhesives, check with your adhesive supplier for an appropriate rubber or neoprene bond; that is an adhesive that will not degrade those materials. Most powder coatings are fairly impervious to most adhesives. Remember: you can always test the adhesive and powder coat for suitability before introducing the combination to full scale production."

"In the US, direct gas fired cure ovens are exhausted at 12 air changes per hour, or higher, to eliminate yellowing of light colored powder coatings. Exhausting of the combustion gases is important for light colored powders used on high quality parts. If the exhaust rate is 12 or more air changes per hour, look to overbaking the powder as the next most contributory cause of yellowing.

Upon occasion, although rare, indirect fired gas ovens, electric convection and IR ovens, or gas fired IR ovens are used to eliminate all problems with combustion gasses. Be aware, that US manufacturers of white powder coated products such as fluorescent lights, appliances, etc. cure their products with direct fired gas combustion ovens without yellowing problems."

"I suggest that you contact a local job shop that offers powder coating services. If you are going to coat your exhaust system, choose a silicone formulated powder manufactured for high-temperature applications."

"There are over 70 suppliers of powder coating materials in the US. Most of these companies will have what you need. I suggest that you contact the Powder Coating Institute for a list and start calling them for samples."

"Call a plating rack manufacturer, like Associated Rack. They have the technology you want."

Usually, PVC coating of dishwasher racks is performed by the major appliance manufacturer who is making the dishwasher. This product has been coated by fluidized bed methods for many years. However, very few people are doing it. I hope this answers your question.
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"Powder application equipment has been used in many "non-finishing" applications. I know of several instances such as: talc on rubber sheet, seasoning on food products, etc. The problem with these applications is getting the equipment suppliers interested in designing a specialized system for these "unusual" applications. Since the market for these systems is small, they normally cannot recapture the up-front engineering costs. However, a specialized engineering firm, such as ours, has been used to develop these applications under the control of the actual end user."
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Normally a zinc phosphate, not an iron phosphate, would be applied over a G90 substrate to achieve 1000 hours of salt spray resistance. Iron phosphate probably won't provide as high a salt spray resistance (i.e. 650+ hours). The TGIC powder would provide excellent weatherability for outdoor applications but won't effect the salt spray resistance on a scribed panel.

If, in fact you are using this substrate, pretreatment, and powder combination, then you would probably have more than 1/8 inch creepage and possibly some loss of adhesion after 1000 hours of salt spray exposure. Be aware that zinc phosphate has some waste water pollution considerations that are very different than iron phosphate. However, if 1000 hours of salt spray resistance is a requirement for your product, then you have little choice."
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"Because of powder coating's high resistance to solvent, finding one to break this bond may be difficult. You can try to cut the coating in the area of the screw head before turning the screw.

I would suggest that your supplier install the stainless screws after coating, so that they can be easily removed by you. I know they won't match in color, but stainless looks great uncoated."
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"Always chromate before you powder coat if you want the corrosion protection under the powder coating surface. This technology will offer 5000 hours of salt spray protection."
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