Question 1. Why Is Powder Coating Superior To Traditional Solvent-based Paints?
Powder Coating has actually been around since the 1950’s but it wasn’t until the 1980’s that it started to become popular as a means of coating metal parts. What was once reserved for heavy industrial applications and mass production is now completely accessible to the home-owner, the hobbyist, and the enthusiast.
Question 2. What Is Powder Coating?
Powder Coating is a method of applying a decorative and protective finish to virtually any type of metal. The powder used in the process is a mixture of finely ground particles of pigment and resin, which is electrostatically dusted onto the surface of the parts to be coated. Flowing from a special powder coating gun, the charged powder particles adhere to the electrically grounded surfaces. The part then goes into a curing oven until the powder is heated and fused into a smooth coating. The result is a uniform, durable, high quality and attractive finish. Powder coating is the fastest growing finishing technology in North America, representing over 10% of all industrial finishing applications.
Question 3. Why Choose Powder Coating Over Traditional Solvent Based Paints?
Powder coating is more durable: Powder Coating gives consumers, businesses, and industries one of the most economical, longest lasting, and most color-durable quality finishes available on virtually any type of metal. Powder coated surfaces are more resistant to chipping, scratching, fading, and wearing than other finishes. Color selection is virtually unlimited with flat, satin, gloss, high gloss, metallic, candies, clear, iridescent, fluorescent, wrinkle, hammer tone, and glitter finishes available. Colors stay bright and vibrant longer. Texture selections range from smooth surfaces to wrinkled or matte finishes, and rough textures designed for hiding surface imperfections.
Powder coating is environmentally friendly: Solvent based paints are notorious polluters as the compounds contain volatile organic compounds (VOC’s). Powder coating, on the other hand, contains no solvents and releases negligible, if any, amounts of VOC’s into the atmosphere. Therefore, there is no longer a need for finishers to buy and maintain costly pollution control equipment.
Powder coating is very cost effective: Since powder coating only uses the material required to coat the part, versus a whole mixed gallon or quart of paint, as well as the elimination of hardeners and catalysts, the material cost is greatly reduced. Prep time beyond sand blasting and cleaning is very minimal which cuts down on labor.
Question 4. What Can Be Powder Coated?
Thousands of products and parts are currently powder coated: such as appliances, car parts, motorcycle parts and frames, bicycles, lawn and garden furniture, antiques, and so on. Typically, if it is a metal part, it can be powder coated.
Question 5. Is There Anything Different In The Pretreatment/wash System For Powder Coatings Vs. Liquid Paints?
Powder coatings can provide improved performance over liquids when applied to a properly pretreated part. Solvent-borne paints are usually more forgiving of organic soils left on the work piece by sub-par cleaning. Because powder does not have solvents, you need to make sure the washer does a good cleaning job. This is just good operational practice and is not an unusual requirement. Iron phosphate is the most frequently encountered pretreatment used with powder coatings. However, if the highest level of performance is required, zinc phosphate will work admirably with powder as well.
Question 6. What Is The Best Cleaner For Powder Coating?
There is no stock answer for this question. Many factors go into deciding which cleaner is the best for your application. Base metal of the work piece, soil being removed, bath temperature, contact time, oil removal capabilities, environmental considerations, etc. must be taken into account when deciding. The bottom line is that you need to get your parts clean, safely, so the steps following in the pretreatment process will function properly. Check with your pretreatment supplier to determine your best course of action.
Question 7. What Different Technologies Are Available For Cleaners?
There are powdered and liquid cleaners. There are acid cleaners that may be best for inorganic (metallic) soils. Alkaline cleaners are often recommended for organic soils. Neutral cleaners may be used to remove soils on substrates that react with strong acids or alkalis (aluminum or zinc). Oil splitting cleaners may be desirable where high levels of oil build quickly in the process bath. Work with your pretreatment supplier to determine which cleaners are best for your application.
Question 8. What Do I Need To Know About Waste From Pretreatment Processes?
Generally, oil and grease, metals (zinc from the substrate, or the zinc phosphate bath), and pH are the concerns from an environmental reporting standpoint. However, sludge or contaminant buildup in the cleaner and phosphate stages may force regular cleanout of these stages. The waste treatment process is usually a simple pH adjustment and flocculation. However, consult your treatment chemical or waste equipment supplier to assure acceptable results.
Question 9. Why Does Powder Surge From The Gun?
Not enough supplemental or forward air to keep the powder in suspension while moving through the powder hose.
Improper seal between the powder injector and the lift tube in the gun feed hopper.
Possible blockage in the power path from build up or impact fusion. Check the gun tube, powder hose, and pump insert.
Question 10. What Does Proper Fluidization Look Like?
The fluidized material should take on fluid-like characteristics. It should have an appearance similar to that of water simmering on low heat. The material should not be boiling hard.
Question 11. What Is Impact Fusion?
Friction may cause powder particles to fuse along the walls of the powder hose and other components in the powder delivery path. Impact fusion is the combining of these powder particles to form a solid mass during the delivery and application process.
Question 12. Why Do I Need To Add Virgin Powder To My Reclaim?
As virgin powder is applied, the larger particles more readily stick to the part. This leaves the over sprayed powder with a lower average particle size. As this occurs during each cycle through the system, the recovered material may become laden with fine particles. Eventually, the reclaimed material will be nearly unmanageable in both fluidization and application.
Question 13. What Is An Acceptable Ground For Maximum Transfer Efficiency?
Uncoated metal parts, clean hangers, and clean conveyors have very little resistance to ground and are excellent electrical conductors. What can degrade this ideal path to ground is powder build-up on the contact points of the hangers or conveyor. Also the conveyor may have swivels or indexing assemblies that, when contaminated, can impede grounding. All of these in total must not exceed one megohm resistance to ground. A Megger (an ohm-meter that has a megohm scale), which has a power source of 500 volts or higher, is typically used to measure continuity to ground.
Question 14. Is Powder Hazardous Waste?
Practically all powder coatings are not hazardous waste by definition of the Resources Conservation and Recovery Act regulations (RCRA). Disposal methods for waste powder are the same as for non-hazardous wastes, in most states. However, there may be some exceptions and your powder supplier should be contacted regarding proper disposal. Always renew disposal needs with the local authority having jurisdiction over your facility location.
Question 15. How Do You Know If Powder Is Cured?
There are two conditions that must be met to achieve proper cure of a powder coating. The first is temperature, referred to as metal temperature, and the second is time. The time/temperature requirements of a particular powder material must be achieved to obtain a full cure. A cured thermoset powder coating will not re-melt upon further heating. To ensure proper time and temperature it is often best to test using a Datapaq or similar device to provide actual performance data.
Question 16. Does Particle Size Make A Difference In Powder Coating?
Particle size plays an important role in the application process. Size distribution affects many other properties critical to consistent performance including: fluidization, powder transport in hoses, uniform cloud density, powder movement in air, electrostatic charging, deposition and build rate, transfer efficiency, Faraday cage penetration, wraparound, and film smoothness. Size distribution produced by the powder manufacturer must take the coating system design and anticipated changes into account to provide a suitable product. Final cured surface appearance may also be affected by the particle size distribution and flow rate.
Question 17. Are There Powders For Interior Or Exterior Use?
One of the most important considerations in defining the end use performance is weatherability. Outdoor exposure results in absorption of ultraviolet energy. This energy can attack the organic binder and result in gloss loss and color change. Due to a tendency to chalk, epoxies and epoxy containing hybrids are generally not recommended for outdoor use when aesthetics is a primary concern. Polyesters and acrylics on the other hand provide excellent UV light stability and typically find use in architectural, automotive, lawn and garden as well as outdoor furniture markets.
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