Powder coating is a dry finishing process that has become extremely popular since its introduction in North America over 40 years ago. Representing over 15% of the total industrial finishing market, powder is used on a wide array of products. More and more companies specify powder coatings for a high-quality, durable finish, allowing for maximized production, improved efficiencies, and simplified environmental compliance. Used as functional (protective) and decorative finishes, powder coatings are available in an almost limitless range of colors and textures, and technological advancements have resulted in excellent performance properties.

How Powder Coating Works
Powder coatings are based on polymer resin systems, combined with curatives, pigments, leveling agents, flow modifiers, and other additives. These ingredients are melt mixed, cooled, and ground into a uniform powder similar to baking flour. A process called electrostatic spray deposition (ESD) is typically used to achieve the application of the powder coating to a metal substrate. This application method uses a spray gun, which applies an electrostatic charge to the powder particles, which are then attracted to the grounded part. After application of the powder coating, the parts enter a curing oven where, with the addition of heat, the coating chemically reacts to produce long molecular chains, resulting in high cross-link density. These molecular chains are very resistant to breakdown. This type of application is the most common method of applying powders.

Powder coatings are easy to use, environmentally friendly, cost effective, and tough!

Durability of Powder Coating
Powder coating is a high-quality finish found on thousands of products you come in contact with each day. Powder coating protects the roughest, toughest machinery as well as the household items you depend on daily. It provides a more durable finish than liquid paints can offer, while still providing an attractive finish. Powder coated products are more resistant to diminished coating quality as a result of impact, moisture, chemicals, utraviolet light, and other extreme weather conditions. In turn, this reduces the risk of scratches, chipping, abrasions, corrosion, fading, and other wear issues.

It's tough. It looks great. And it lasts a long, long time. In addition to being durable, powder coating is an attractive choice due to environmental advantages.

In addition to being the more durable and attractive choice, powder coating is also highly protective of our environment.

Negligible VOCs and HAPs (hazardous air pollutants) Free
Powder coatings contain no solvents and therefore emit negligible, if any, polluting VOCs into the atmosphere.

Less Exhaust
Powder coating is a clean process, allowing exhaust air from the coating booth to be returned to the plant, and less oven air is exhausted to the outside. Heating and cooling costs are eliminated for make-up air and the cost for maintaining oven temperatures is minimized.

Many issues inherent in liquid finishing are eliminated or minimized with the powder coating process. Liquid finishes contain solvents, which have pollutants known as volatile organic compounds (VOCs). Powder coatings contain no solvents and releases negligible amounts of, if any, VOCs into the atmosphere. Thus, there is no longer a need for finishers to buy costly pollution control equipment, and companies can comply more easily and economically with the regulations of the U.S. Environmental Protection Agency.

Powder coating is a clean process. In fact, one of the major elements in expanding the market for powder coating has been the implementation of stringent air pollution control legislation over the past 30 years. In addition, the increased efficiencies of applying a powder coating generally produce lower operating costs. For example, powder coating overspray that does not adhere to the part can be retrieved and reused. The unused powder is reclaimed by a recovery unit and returned to a feed hopper for reuse. Any powder waste that results is minimal, and can be disposed of easily, economically, and safely.

Powder coating is the smart choice to run the most economical and efficient operation:

Lower Heating Costs for Curing Oven
The exhaust requirements for a powder coating oven are lower than solvent-based coatings, resulting in energy savings.

Greater Operating Efficiency/Lower Unit Costs
No drying or flash-off time is required. Parts can be racked closer together on conveyors and pass more quickly through the production line.

Lower Reject Rates
More parts can be coated automatically with fewer rejects because powder coating does not run, drip or sag.

High Utilization Efficiency
With proper application equipment, powder materials and efficient recovery methods, one-coat application and 95%-98% powder utilization efficiency are realizable versus an average of 60% material utilization with an electrostatic liquid system.

Production Flexibility
If more than one color is desired, color changes can be made quickly.

Minimal Training Requirements
Minimal operator training and supervision are required for a powder line. Employees prefer working with dry powder due to the lack of fumes, reduced housekeeping problems and minimum clothing contamination. A simpler coating process leads to less coating errors which results in minimal scrap, reduced labor costs, and reduced operating costs.

Simplified Permit Process
The permitting process for a powder coating operation is simpler. Compliance with federal and state regulation is also easier, saving both time and money.

Epoxy

Epoxy coatings are used wherever a hard, electrical insulating coating is required to provide protection over a wide temperature range. Depending on the particular epoxy selected, these coatings can be used up to 150°C or higher. They are, therefore, ideal as functional electrical insulators as well as a protective coating. Chemical resistance to most solvents and mild acids and bases is good, and epoxy powder coatings provide excellent toughness and corrosion resistance. Adhesion to metal substrates is excellent, and generally epoxy powder coatings do not require a primer. The major limitation of epoxy powder coatings is a tendency toward brittleness if the coating is over a few mils thick. They will also chalk when subjected to UV radiation. For this reason, they are rarely used for outdoor applications. Epoxies are often used for decorative applications. They can be formulated to provide a variety of colors, glosses, and textures. Typical applications include metal office furniture, shelving, interior car parts, and toys.

Hybrid

Epoxy-polyester hybrids combine epoxy resin with polyester resin to form a powder with many of the same characteristics as the epoxies. This group of powder coatings could be considered part of the epoxy family except for the high percentage of polyester utilized (often in excess of half the resin). Property wise these resins are very close to their epoxy counterparts. Epoxy-polyester hybrid coatings are generally tough, flexible, and competitively priced when compared to pure epoxy coatings. Hybrids provide some improvement in weatherability, but they will begin to chalk almost as fast as an epoxy coating. However, after initial chalking, the deterioration is slower. Some hybrids are less resistant to chemicals and solvents. Hybrids are likely to be used in many of the same applications as epoxies.

Polyurethene

Polyurethene powders are one of the two polyester powder coatings being used commercially (the other is polyester TGIC). The primary type that has been used for several years is a urethane cured polyester powder, which is comparable chemically to the exterior quality urethane paints that have been used on aircraft, buses, trucks, etc. Coatings of this type combine outstanding thin film appearance and toughness with excellent weathering properties. Polyurethene powder coatings are true competitors to high quality liquid paints in respect to thin film appearance. They are used for exterior applications such as patio furniture, automotive wheels and trim, lawnmowers, and a wide range of other products requiring high quality, decorative finishes.

Polyester TGIC

Polyester triglycidyl isocyanurate (TGIC) powders are one of two polyester powder coatings being used commercially (the other is polyurethene). In these coatings a very low molecular weight glycidyl or epoxy functional curing agent is used to co-react with the polyester. In this way, the polyester constitutes a very high percentage of the resin and provides weather and corrosion resistance incomparable to the polyurethene. However their resistance to chemical and solvents is lower. TGIC powders have very good adhesion characteristics, corrosion resistance, and exterior durability. They can typically be cured at lower temperatures than urethanes and have shorter cure cycles. They also provide good edge coverage and tough, thick films. Typical applications of polyester TGIC powder coatings are where sharp edges and corners exist such as on automotive wheels, air conditioners, lawn furniture, and air conditioner cabinets.

Lets go through the process from start to finish. First we will powder coat a Chevy LT1 intake manifold in a Mirror Red. Next we'll powder coat a Nissan SR20det valve cover in Candy Purple. Hope you enjoy.