Powder coating is a method used to apply a protective and decorative coating to products such as white goods, aluminum extrusions, and automobile and motorcycle parts. Newer technologies have allowed other materials, such as medium-density fiberboard (MDF), to be powder coated using different methods. First used in Australia in 1967, powder coating has become one of the most popular surface finishing techniques in use today.
Powder coating uses a very fine dry powdery-resin that contains a color pigment. The resin is charged by electrostatic methods and then using a spry gun is applied to the metal surface. Because the powder is charged it will adhere itself to the surface of the metal. The metal is then placed inside an industrial oven and baked at approximately 400 degrees or more, which will cause the powder to allow it to flow and form a skin that is more uniform and durable finish, which is resistant to chemicals, wear and tear, and chipping.
Powder coating is expensive, so why should anyone spend that much money. To answer that question, I can only say---You get what you pay for. Yes, powder coating does look just like liquid paint. However, it will protect your motorcycle or other item as if you?ve coated it in armor. Powder coating is an extremely durable, very decorative finish that will out last any liquid paint finish applied to products. It is so popular, that nearly every quality made item is powder coated from appliances, to furniture to the clear powder topcoat on many automobiles. Powder coating is available in virtually any color or finish, including matte or smooth imaginable. It is rust-free, scratch resistant, chip, resistant, resistant to acids and solvents, and it is ecologically friendly.
The electrostatic powder coating system is the application of electrically charged powder coating materials to grounded object or parts. The object is then heated causing the powder to flow and cure. However, if the uncured powder coat is damaged or blemished in any way, then the powder can simply be blown off with air or vacuumed and a new powder coat applied.
There are four basic pieces that make up the electrostatic powder spray coating system, which are the powder feeder, power unit, electrostatic spray gun, and powder booth recovery system.
The spray gun is supplied with powder from a feeder unit, which diffuses the powder with compressed air into a fluid- like state. High velocity air flows through a venturi and siphons out the fluidized powder, which is then propelled through the powder feed tubing to the spray gun.
The powder feeder also allows for a controlled flow of powder to the guns. The system has independent controls for powder and air volume, which allows for adjustable dilution ratios so that the desire thickness coverage can be attained for each object. The powder feeder has the capability of providing ample discharge pressure and velocity to feed an electrostatic gun to approximately 25 feet away.
When the powder leaves the spray gun, it does so in the form of a diffused cloud, which is propelled toward the workpiece. A charging electrode at the front of the spray gun is powered by a high voltage, low amperage power unit, which emits a field charge that imparts a negative charge onto the particles of powder. This negative charge causes the powder to seek out and attach to the grounded work piece.
In closing the functions of the electrostatic powder spray gun are to shape and direct the flow of powder, control the size, shape, and density of the powder pattern, impart an electrostatic charge to the powder being sprayed and control the accumulation of powder onto the objects that are being coated.
When purchasing the equipment you will need for powder coating, the most expensive investment will be the oven. Once the part or object has been powder coated it is then placed in the oven, where it is baked at 400 degrees Fahrenheit for 10 minutes. If you do not have an oven that will allow you to bake items at 400oF for 10 minutes, you cannot powder coat.
As the part bakes in the oven, the powder paint melts, flowing into a beautiful and very durable finish that doesn't contain any unsightly runs or drips, which are often seen when wet paint is used. If mistakes are made prior to baking, the powder coating can easily be blown with a low-pressure air nozzle and the part recoated. However, once the item has been cured in the oven, mistakes can only be corrected by removing the finish with sand blasting or burning it off. There are cold liquid strippers available, however they are extremely slow, and hazardous and have been known to damage the metal.
When choosing between gas and electric ovens, they both work equally well. If properly designed, infrared ovens work well also. Electric ovens do have one drawback in that they take longer to reach the proper baking temperature. Therefore, if this will be a problem for you, then gas should be your best choice.
When powder coating, the finish is very durable. However, chipping can be a problem with powder coating if the part was not baked long enough and/or kept at the proper cure temperature.
Nearly any metal part or object can be powder coated. However, in order for parts to be powder coated, they must be able to withstand the curing temperatures of approximately 350-450F for 15-30 minutes. Because of this, parts such as cylinder heads, that are made out of plastic substrates or other materials that might warp cannot be powder coated unless low cure powders are used. Unfortunately, many paint shops are not skilled in this application.
In addition, the parts must be able to also endure the powder coating's additional thickness, as they are thicker and heavier than liquid paint. Parts such as cylinders and cylinder heads should not be powder coated. These parts are designed to dissipate heat by powder coating these parts it can inhibit their performance.
Other items such as aluminum wheel spindles, wheel billets, scuba tanks, etc. should not be powder coated either unless they are powder coated using cooler curing powders. The reason is that the higher temperatures required to cure standard powder coatings can causes the ductile aluminum to become brittle.
The powder pump supplies powder to the gun in a uniform and steady rate. Powder pumps usually use a venturi to deliver the powder from the supply hopper to the powder spray gun. For first-pass transfer efficiency, the operator wants to use the lowest flow rate as possible while still maintaining coverage through each spray gun being used. The reason for this is that the more powder that passes over the gun electrode creates a shielding so that each particle picks up less of a charge. Therefore, less powder is more effective when dealing with transfer efficiency. To achieve first-pass transfer it is better for companies to add additional powder guns and maintain outputs low than to increase the output of the existing guns. The majority of powder pumps are made with engineered plastic to provide the maximum resistances against wear. In addition, many are available in configurations for either corona-charging or Tribo-charging spray gun systems.
Powder Coating has a far better impact resistance, flexibility and corrosion resistance than that of liquid paints. In addition, powder coating is a very cost efficient and effective alternative to liquid paints, plus it is environmentally friendly, because it is regulated and free from pollutants. Because of these and many more benefits, powder coating is used on literary thousands of products today.
Appliances: The appliance industry uses powder coating on the front and side panels of ranges and refrigerators, washer tops and lids, dryer drums, air-conditioner cabinets, water heaters, dishwasher racks, and cavities of microwave ovens. In addition, powder coating has replaced porcelain enamel on several washer and dryer parts.
Automotive: The automotive industry uses powder coating on wheels, bumpers, hubcaps, door handles, decorative trim and accent parts, truck beds, radiators, filters, and numerous engine parts. BMW and Volvo were the first to use a clear powder topcoat, which provides excellent protection to the automobiles color coat, ensuring that the car will maintain its showroom shin longer.
Architecture/Building: The architecture and building industry has benefited as much from powder coating than any other industry. Powder coating has been used on rebar, tools, as well thousands of commercial, industrial, government, residential, historic and institutional buildings world wide.
Everyday Products: There is an immeasurable amount of everyday products that are powder-coated including lighting fixtures, antennas, and electrical components, tractors, farm equipment, golf clubs, golf carts, ski poles and bindings, snowmobiles, bicycles, and exercise equipment, display racks, shelves, store fixtures, and vending machines, office equipment, metal furniture, computer cabinets, mechanical pencils and pens, thumbtacks, and other desk accessories. Other items include baby strollers, cribs, metal toys, wagons, tricycles, hobbyhorses, etc. Around the home the following you?ll find that the following items are also powder coated: lawn mowers, snow blowers, barbecue grills, patio furniture, garden tools, electronic components, bathroom scales, toolboxes, and fire extinguishers. Nearly every product that we use today is powder coated, which ensures that we will be able to use that item longer.
Non-Metal Products: If you thought that powder coating could only be used on metal, guess again. Because of recent technology developments of powder that can be cured at lower temperatures, powder coating can now be used on ceramics and some wood and plastic applications. Powder coating on wood has grown to include such items as home- office furniture, kitchen cabinets, children's furniture, and outdoor grill tables. Powder coating ensures that these products retain their new look much longer.
