Industries today are toting the advantages of powder coated finishes!  A notable alternative to liquid paint, powder coating has gained popularity as a dry finishing process used to protect the toughest industrial machinery, as well as common household items including electronics and appliances. The powder used in this process is comprised of finely ground particles of pigment and resin, which are sprayed onto a surface to be coated and baked to a fluid state. Powder coated products have proven to be more durable and resistant to moisture, chemicals and ultraviolet light than liquid paints, while toting an attractive and high-quality finish. Whereas, standard paints can take days to cure and are dependent on atmospheric conditions, powder coated products are ready to use within 20 minutes of heat curation and produce a much thicker coating that will not sag or run. In addition, powder coatings meet all Environmental Agency Protection requirements for air and water pollution control. These materials are generally free of volatile organic compounds (VOCs) and the potentially harmful solvents found in wet paints, minimizing risks to workers and reducing industrial pollution concerns.

Powder coating can be divided into two primary categories; thermoplastic powder and thermoset polymer. Thermoset powder coating differs from thermoplastic powder in that it undergoes a chemical change as it cures and cannot be remelted or reused. This change is referred to as crosslinking. On the other hand, thermoplastic powders remain chemically unchanged throughout the process  and are able to be reused and remelted. This type of paint is generally applied to a part that is is heated to a temperature well above the powder’s melting point, causing the powder to melt and form a scratch-resistant, uniform film of paint.

The four basic resins used for thermoset powders are epoxy, acrylic, polyester and fluropolymer.  Polyester resins rank high in popularity among powder coating paints, as they offer excellent corrosion protection and extreme weather protection. On the contrary, expoxy-based powder coating is typically limited to indoor applications due to its ultraviolet and harsh weather sensitivity. In architectural and highly corrosive environments, fluoropolymer powders fare well due to their high quality, weather-resistant finish, while acrylic thermosetting powders offer a chip-resistant, high-gloss finish ideal for the automotive industry.

Powder coating involves a multi-step process which includes part preparation, powder application and high-temperature powder curing. Prior to coating, each part must be properly cleaned of dirt, grease, oil, metal oxides, or other substances that may interfere with the painting process. Poor pretreatment practices may lead to a number of issues including loss of adhesion, pinholing, outgasing, weld pull away and premature coating failure in harsh environments such as salt air. In order to achieve superior performance and weathering characteristics, a good pretreatment, such as etching or phosphating is recommended. Such treatments help prevent flash rust prior to powder coating and provide for long-lasting physical bonds.

Alvin’s Lab-Metal and Hi-Temp Lab Metal may be used to patch, smooth, repair and seal items that need to be powder coated. An ideal filler for dents, voids cracks and other surface blemishes, Lab-Metal Repair and Patching compound adheres well to most clean, dry surfaces and can withstand vibration and other difficult conditions. For powder coating processes running above 425 degree F. Hi-Temp Lab-Metal must be used and applied in thin, 1/4 inch, layers. Allow for a minimum drying time of 24 hours, then heat cure. Lab-Metal, on the other hand, may only be used in instances where metal parts will not be exposed to temperatures topping 425 degrees F. for longer than 20 minutes and should be applied no thicker than 3/8 inch.

Following pretreatment, the object must be completely dried before powder is applied. The most common way of applying a powder coating is through the use of an electrostatic gun. The powder is electrically charged as it is applied to the part, giving each particle of the powder a negative charge. The part being powder coated is electrically grounded as a means of attracting and attaching the powder to the part’s surface. This electrostatic attraction is a key element in the process, aiding the coating evenness and the speed of applying the coating. The result is a uniform coating of dry powder clinging to the part.

Once the part is coated with powder, it must be moved into a curing oven. There the powder gels, flows and cures to produce a smooth, durable powder coat finish. During the curing process, crosslinking takes place. It is at this point that the part can be removed from the oven, cooled in ambient air, and put into service.