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This section explores powder coatings, the details about powder coatings, and how they differ from liquid coatings.

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Powder coating is a paint finish that is industrially manufactured in a powder form. Polymer granules are mixed with other ingredients and then broken down and milled into a fine powder. It is factory applied and cured, and applied to metal components or other materials, such as medium-density fiberboard. Powder coating works well for a range of applications, and unlike liquid paint, powder coating does not require a solvent. It creates a thicker, more durable coating than conventional paint.

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Powder coatings are formulated with several different raw materials. The main ingredients that go into a powder-coating formula include resins that make the coating durable yet flexible and pigments that cover the substrate and add color. Also integral are fillers, cure agents, and flow agents. The formulation is geared toward the intended end use. For example, a resin is selected based on the properties that best suit its purpose. A powder coating intended for outdoor use would incorporate a different resin that can tolerate UV exposure and temperature extremes and excessive moisture or other conditions that are not common for an indoor appliance. Desired gloss, texture, and other aesthetic properties are incorporated into the formulation process.

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Powder coatings were first developed in the late 1940s and early 1950s in Europe in response to health and environmental concerns. At that time, liquid paints contained solvents that polluted the environment and had harmful health effects. Powder coatings, by contrast, were considered a major advancement in technology to replace liquid finishes. Europe first developed powder coatings to help mitigate environmental worries, and this reason continued to maintain a hold on the increasing use of powder coatings as stricter limits on industrial emissions came into play in the 1970s. Powder coatings continue to mitigate environmental and health concerns today.

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The first application for applying powder coating was a process of flame spraying, like welding with an acetylene torch. Flame spraying brings together acetylene or propane with oxygen to melt powder that is then fed by compressed air directly into the flame and then applied to the surface. Recently, the National Center for Manufacturing Sciences looked at flame spraying to evenly cover large or odd-sized objects. It wanted to optimize parameters and performance. The group also focused on the benefits of powder coatings because they help eliminate volatile organic compound (VOC) emissions, limit solvent exposure for workers, and also can add a corrosion-resistant layer to parts. New reference: www.ncms.org/powder-coating-flame-spraying-technologies-maintenance-sustainment/

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Between 1958 and 1965, the fluidized bed application was developed as an efficient alternative to flame spraying. This application is a simple dipping process that includes a tank with a porous bottom plate as the fluidized bed. Rising low-pressure air surrounds and suspends the powder, like a boiling liquid. Preheated objects are dipped into the fluidized bed, where they are coated with a thick substance of color. Another method of application involves heated parts passed through an electrically charged cloud of powder above a container of fluidized powder. Most of these applications provided a film thickness of 6 to 20 millimeters. This application was introduced to the U.S. market as a way to insulate electrical components.

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In the early 1960s, the process of electrostatic spray coating was developed by Pieter de Lange and is still a common application method. Powder is applied in one of two ways. Either the substrate is dipped into a vat or it is sprayed by a powerful electrostatic charge. Both processes are followed by curing in an oven.

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Powder manufacturing began to spread globally in the early 1970s. A rapid-growth phase in powder production began in North America and Japan in the early 1980s. Application improvements led to increased transfer efficiency, reduced waste, and lower overall costs. The automotive, appliance, and industrial markets drove the developments as the sophistication of materials, manufacturing, and applications improved.

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This section will describe powder-coating applications, processes, and their development. Powder mixing, extruding, chipping, application, and curing are covered. The reusability of excess powder also is covered to show how any overspray can be collected and recycled, making the powder-coating process very efficient.

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Powder-coated products can be highly resistant to extreme weather conditions, impact, moisture, chemicals, and light. To make a fine powder that will adhere and last, materials are first weighed and sent to a vessel that collects the materials in the right ratios to match the formula for a specific type of powder. Raw materials include polymer granules, resin, pigment and a monoflow agent. From the vessel, the materials are transferred to a high-speed mixer and mixed for 30 to 90 seconds, blending them into a homogeneous mix.

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Next, the pre-weighed and premixed powder is heated in an extruder. The extruded material is rolled flat between two chilled rollers and allowed to cool before being chipped into flakes. The chips are micronized—ground into a fine powder like baking flour. Then the powder is put through a sieve to omit any excess particles. These larger excess particles are micronized again to complete the mix. The powder is then packed in plastic, boxed, and ready for shipping.

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Pretreatment and cleaning of the object or substrate is essential prior to the application of powder coating. Unlike liquid coatings, the powder requires no primer, but the substrate must be cleaned and pretreated for proper application and adhesion to the surface. Typically, the process starts with the application of a cleaning and etching solution. Three water rinse cycles follow, the last with deionized water. Finally, a chemical pretreatment is applied. With powder coatings, a chrom- based pretreatment or a non-chrome pretreatment can be used. The object is then dried in an oven before coating.

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Powder coating can be applied manually to the object, or the object can be run through an automated paint booth. The powder is applied electrostatically. The object can be coated in a powder-coating booth, which is computer operated with banks of nozzles. Stationary or reciprocating guns are used in automated application systems. The computer generates data about the length of the substrate and whether it needs to be sprayed on both sides. The substrate is hung from a rack or conveyor that transmits a negative static charge to the material. At the tip of the applicator, a probe gives the powder a positive static charge as it is sprayed through the gun. This allows the powder to be attracted to the substrate, and minimizes overspray.

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Once the substrate has been coated, the powder is then cured. The coated object is baked in an oven at temperatures ranging from 250 to 400 degrees Fahrenheit. This thermal cure forces the cross-linking of molecules in the resin to make the resulting thermoset coating system. The finished product is an object coated with a hard and durable powder-coated finish.

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The process of powder coating results in some overspray, but excess powder is recyclable and can be collected and reused. There are two main types of powder-collection systems. The most commonly used system is the cartridge-collector technology, which has dedicated cartridges for capture. Less common is cyclone technology, which uses one or more cyclones to reclaim powder. Reclaiming unused powder and returning it to the hopper for recirculation leaves minimal waste. Taking into account the transfer rate of powder to an object—and the amount that is captured from the air as overspray—powder coating ends up an average 93 percent efficient, or better stated, only has around 7 percent waste. References: www.powdercoating.org/?page=EnviroImpact www.powdercoatedtough.com/News/ID/465/Powder-Coating-Reclaim-Considerations

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Powder coatings have many attributes that are positive. A helpful way to remember the benefits is to refer to the so-called “Five Es:” efficiency, economy, energy saving, environmentally friendly, and excellence of finish. In the following section, we will explore in detail what sets powder coating apart from liquid coatings, as well as the environmental and health benefits.

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Now, let’s take a look at liquid paint. A typical gallon of liquid paint consists of 40 to 45 percent solids, such as resins and pigments. That being said, it also contains solvents—up to 60 percent. Solvents are used to adjust curing and viscosity of paint. They do not stay as a part of the paint film, but control flow and stability. In a sense, a solvent is a carrier for the paint application. Solvents are volatile organic compounds, or VOCs, and are regulated at federal, state, and local levels. Air quality, water quality, waste disposal, and human health are all negatively affected by VOCs. Once in the atmosphere, they create smog, which attacks lung tissue and is very harmful even in low concentrations. Solvents are also a hazard to installers or workers directly exposed to the chemicals. Powder coatings, on the other hand, are solvent free and thus do not have these potential risks.

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Powder coating is a more predictable and sustainable alternative to “wet” paint finishes or anodized finishes. When wet paint cures, it shrinks down to less than its original thickness. For example, 2 millimeters of powder coating will cure and still be 2 millimeters of powder coating. With liquid finishes, all the solvent dissipates into the atmosphere as VOCs. The end result is a dry-film thickness that is thinner—instead of 2 millimeters, for example, just 1 millimeter with liquid paint. This leaves a thinner less durable finish than powder.

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Liquid paint is more hazardous than powder coating in part because it contains flammable solvents. It requires more effort and special permits for cleanup and hazardous waste transportation, as well as hazardous waste disposal. Also, liquid coatings use oxidizers to burn off VOCs. Liquid coatings require red label storage, special fire permits, and environmental emissions permits.

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Powder coatings offer exceptional durability and look like liquid coatings. They are high-performance architectural coatings that do not use solvents but have the same tested outcomes as parallel liquid paints. Liquid paint is essentially pigment, resin, and solvent, where powder coating is pigment in a powdered resin but without the solvent. Powder coatings and liquid coatings made from the same resin and pigment offer similar outcomes with significant benefits achieved from the powder.

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Let’s take the high-performance American Architectural Manufacturers Association (AAMA) 2605 exterior powder-coating specification and compare it to the 2605 liquid paint. The powder coating is formulated with 100 percent fluoropolymer resin. The comparable liquid paint calls for a minimum of 70 percent fluoropolymer resin and is often combined with other less durable resins. It’s important to note that when the solvents from liquid paint evaporate, they can leave a porous surface that is less resistant to chemicals and industrial cleaners. When it comes to high-performing, sustainable, and durable powder coatings, there are two types of resin-based coatings that meet or exceed the 2605 standard and stand up to corrosion, UV light, and humidity. They are called PVDF (polyvinylidene difluoride) resin and Feve resin. Feve resin is used in many architectural grade powder coatings with a single-coat system that offers the same or better performance of the two-coat PVDF system. The Feve resin is especially tough because it is thermoset, meaning it cannot be remelted, offering superior toughness and scratch resistance. Both PVDF and Feve-based powder coatings work well, meet or exceed the standard, and offer excellent warranties and protection.

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Powder coatings are denser and provide better corrosion resistance than liquid coatings. Powder coatings typically have a higher buildup of film that offers improved chemical resistance. They resist scratching as shown by their performance under a pencil hardness test. Unlike liquid PVDF coatings, a thermoset fluoropolymer powder forms a hard, durable film to provide excellent scratch and mar resistance. Powder coatings weather well and comply with AAMA 2603, 2604 and 2605 specifications. AAMA 2605 is the high-performance exterior specification. These finishes are resistant to moisture, weathering, ozone, and UV radiation. An application for this finish would include architectural projects like bridges and structural load-bearing members that require long-term cosmetic and functional protection.

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Another major advantage of powder coatings is the vast range of colors, glosses, and textures that goes beyond what liquid coatings offer. There is a wider aesthetic choice of finishes in an array of color schemes. Powder-coating selection also includes a broad range of gloss coatings—more than liquid PVDF coatings provide. Another interesting feature is that there is a good selection of contemporary textures and patterns for powder coatings. Finally, unlike liquid coatings, powder coatings leave vertical and horizontal surfaces more evenly covered.

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Powder coatings are not considered hazardous, so when working with powder coatings, there are no special storage requirements, such as those required for liquid paints. Another advantage over liquid paint is that powder coatings are a single-coat system and thus do not require primers. Finally, a powder-coated surface is not only durable but also easy to clean, lending itself to a wide range of interior and exterior applications.

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Powder coatings are nonflammable because they do not release solvents into the environment before, during, or after application. This prime characteristic makes them considerably cleaner and safer to use. Powder coatings have a considerably lower fire risk since they are solvent free. This lower risk can be an important benefit to the health of operators who are involved in applying powdered paint to substrates as opposed to liquid paint. Reference: www.thefabricator.com/article/finishing/safety-and-regulatory-overview-for-powder-coating

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Even though powder coating is safer than liquid paint in some ways, applying it is a production process and requires the correct safety precautions. The main risk is that the potential of combustion, as the powder is in an atomized state. For example, the object to be painted must be grounded to the rack. To help ensure this, operators should have racks and fixtures regularly cleaned of any build up. Also as a precaution, some local regulations may require flame-detection equipment.

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As we noted earlier, powder coatings do not contain solvents or VOCs. There are not any toxic compounds in the powders and so the environmental effects are minimal. Disposal of powder-coating waste can take place in a landfill because it is not hazardous. Liquid paints, however, require special disposal techniques to avoid contaminating groundwater or causing a fire. Liquid paints also produce hazardous waste that has been proven to harm the environment by producing ground-level ozone, a principal component of smog that causes negative effects on the lungs, including difficulty breathing and lung damage, worsening of asthma, coughing, and chest irritation. Powder coatings do not affect human health in this way. Reference: www.spartaengineering.com/powder-coating/

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The general application of a single coat of a powder finish is economical and efficient. Application of powder coating takes one shot; single-coat applications are the most common method of powder coating and reduce time and energy. There are exceptions, however, when a two-coat system of powder coating helps create a special effect such as a texture or pattern on the surface. The base product for powder coating also costs less than wet paint. While the cost to buy and run an oven to bake and cure powder coating can be high, the substrates tend to cool and be ready for use very quickly, in as little as 20 minutes. Liquid paints on the other hand can take days to dry and be ready.

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The positive economic results from choosing powder coating include that the base product is less expensive than liquid paint. Yet the overwhelming benefit of reusing collected overspray stands out. The ability to reclaim and recycle powder that didn’t hit its target has made powder coating a product with nearly no waste at all. With liquid paint, about 50 percent of the product can evaporate with no possibility of reclaiming it. The EPA recognizes these benefits and has noted powder coating’s valuable benefits in light of VOC emission restrictions, cost, quality, and production. According to the EPA, powder coatings do not produce significant emissions or VOCs or hazardous air pollutants (HAPs). They offer the reduction of VOC emissions to zero. Due to ever-increasing VOC-emission restrictions placed on manufacturers, powder-coating production and use has grown dramatically, the EPA noted, and most are classified as nonhazardous, eliminating or minimizing problems and expenses associated with disposal.

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There are only a few disadvantages to powder coating. Aside from the ovens being costly to purchase and to maintain production through heating, a downside is that the coating cannot be used on rubber surfaces. This is because rubber will melt at the temperature needed to cure the coating. Finally, powder coating cannot be touched up as easily as liquid paint when there are chips or nicks or scratches on a coated part. That being said, powder coating is more resilient than liquid paint and requires fewer touch ups. Reference: www.spartaengineering.com/powder-coating/

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Functional and protective, powder coatings offer the benefits of a lasting coat and an aesthetically pleasing appeal for professional architects. AAMA has specified and tested the three major groupings of powder coatings, from most affordable to most protective.

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Architectural powder coatings add decorative and protective features when applied to architectural aluminum or steel. The coatings are factory applied in a single-coat application. Different coating grades are suitable for interior or exterior applications, and all are made of durable resin systems with top warranties available to the purchaser. Residential, commercial, and monumental applications can benefit from powder coatings, which have come to be known as the green alternative to other finishes. Some companies offer a wide range of finishes and colors, including many choices in gloss and curing responses depending on the desired result. Frames, facades, vents, curtain walls, doors, railings, soffits, and even light posts and fences can be powder coated. As mentioned in regards to environmental and health benefits, some of the touted advantages of powder coating include not requiring a primer, no VOCs, superior resistance to scratching or abrasions, and long life cycles. LEED credits and overall costs are also cited as advantages to powder coatings in architectural applications.

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Some examples of architectural powder coating applications in residential areas include windows, doors, verandas, fencing for homes, and light posts in the neighborhood. The finishing of residential property can include such decorative considerations as trellises, umbrellas, and patio furniture. Other useful things from around the home that take powder coating are kitchen racks, lighting fixtures, handles, drawer pulls, and metal table and chair frames that can be streamlined or modernized with powder coating. Special ordering new colors and textures can help homeowners avoid throwing away old items to buy new ones. Instead, powder-coating businesses do custom work to update furniture in a home. Any electrically conductive metal or object that can withstand 400 degrees Fahrenheit can be powder coated. Powder coating offers a decorative, cost-effective, and environmentally friendly alternative to buying new items, simply by refinishing and giving new life to older products.

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Powder coating for commercial purposes can run the gamut from farm machinery to medical devices to mixing balls for cosmetics. Commercial powder coating companies work on objects of any regular or irregular shape, size, or dimension and usually offer a wide variety of glosses, colors, textures, and chemistries. You might be surprised at some commercial applications, such as musical instruments and cases, grocery carts, ammunition reloaders, speakers, tools, tubing, and city park fixtures. Other uses may be more familiar, such as general powder coating for the agricultural, aviation, aerospace, automotive, plastic, and electronic industries. Commercial powder coating can refresh the finish of aged or distressed items, providing a “like-new” appearance. Other applications include assembly line parts, sheet metal parts, piping, extrusions, castings, and fabrication for mining.

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A monument is made in memory of a person or event and signifies the importance of remembering historic people or times of a culture, and therefore are meant to last. Powder coatings can help them resist the elements and last a long time. Monuments of all sizes and shapes including buildings, sculptures, signage, community art, and memorial markers are protected long term in a way that achieves a desired visual effect with powder coating. Powder-coating applicators offer options suited for outdoor applications and include UV- and scratch-resistant coatings with a range of finishes.

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The appeal of powder coatings in architectural applications is in the range of options from colorful to subdued, as well as the long-lasting results that help lead to more sustainable buildings. Powder coating meets AAMA specifications, and so it is critical to sustainable building projects that focus on low emissions. When building professionals consider interiors such as partitions and ceiling tiles or even suspended ceiling tiles, they often opt for powder coating over liquid paint. Virtually any part or product, including fixtures, lends itself to powder coating, including those made from metal and aluminum composites. In many commercial, industrial, governmental, and institutional buildings across the world, powder coating is applied for its durability against wear and tear and for its diverse appearances. Powder coating formulas can be specified for scratch resistance and gloss retention, and it is unlimited in colors, finishes, glosses, and textures. Metallic pigments for example offer a brilliance fitting for architectural aluminum or office furniture.

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LEED buildings are designed to lower operating costs and increase asset value of a facility. They reduce waste sent to landfills and conserve water and energy. Overall, the intent of the LEED program is to make buildings healthier places that are safer for occupants while supporting sustainable development by reducing harmful greenhouse gas emissions. LEED buildings can qualify for tax rebates, zoning allowances, and other incentives in hundreds of cities. A powder-coated finish may qualify for extra LEED credits under Innovation in Design Credit 1. The Innovation in Design credits provide points for projects that incorporate innovative and sustainable building features that go above and beyond the LEED Rating System requirements or categories. Because power coatings improve durability, they are able to last longer, thus reducing early replacement and helping to keep materials out of the waste stream. Also, the extended life requires less maintenance, painting, and refinishing, which conserves raw materials and eases the demand on natural resources.

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Powder coatings incorporate different resins for each American Architectural Manufacturers Association (AAMA) specification. AAMA is an advocacy group for manufacturers and professionals in the fenestration industry with a focus on creating standards that ensure the highest-quality products are available to architects and builders. To meet the AAMA 2603 specification, a standard polyester resin is employed. These coatings are usually used on interiors such as indoor windows, supports, and ceiling panels, and they offer good resistance to abrasion and scuffing but have limited color retention. AAMA 2604 coatings are an intermediate specification consisting of super durable polyester resins. Balconies and railings treated with this coating have good resistance to wear, and gloss and color retention for five years. AAMA 2605 is the high-performance exterior coating that uses a fluoropolymer resin. Resistant to weathering, moisture, ozone, and UV radiation, these coatings are applied in architectural projects that call for durable long-term protection. Each AAMA specification requires coatings to be tested for chemical, mechanical, and weathering resistance. Once the AAMA specification has been met, powder-coated products can then be included in the sustainable design plan for the project. The more stringent the AAMA specification, the more durable and thus sustainable the product will be.

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Displayed in the graphic is the range of testing a coating is subjected to when establishing AAMA specifications. It shows how each specification holds up to the various tests and also compares the performance to liquid finish. As you can see, chemical resistance and dirt resistance are measured over time, as well as toughness and number of coats required. Use of sludge or solvents is listed, as well as the occurrence of VOC emissions. AAMA 2605 and PVDF liquid are comparable up to the point of excellent resistance to dirt and chemicals, but there the parallels end. PVDF liquid requires solvents, sludge, and multiple coats of color. AAMA specified powder coatings do not.

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The three AAMA standards, 2603, 2604, and 2605, are progressively stronger levels of powder coating that have been tested in south Florida at an outdoor exposure lab that produces laboratory accelerated testing results. South Florida exposure is a standardized real-world test that analyzes a wide variety of powder coatings for their resistance to chalk and erosion as well as color and gloss retention. The color retention test at the south Florida lab represents the degree to which a coating’s color is degraded as a result of exposure to UV radiation from sunlight. The chalk resistance test is a visual inspection to examine how much a coating chalks from weathering. The erosion weathering test represents how resilient a coating is to the effects of the elements.

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The AAMA 2603 finish is considered the “basic finish” and uses standard polyester resins for baseline market products. This panel was tested for one year in south Florida. After one year, there was no checking, crazing, or loss of adhesion after taping. In addition, there was only slight chalking and fading. Standard polyester coatings like this can be used reliably for a wide variety of interior applications. These coatings are usually used on window and door frames, trim, railings, and a variety of other interior uses. They can provide color control, film integrity, and resistance to impact and marring.

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This AAMA 2604 specification is the intermediate coating considered stronger and more durable than 2603. It is tested for five years in Florida. This powder is based on super durable polyester resin and is a standard finish for many windows, doors, curtain walls, storefronts, and skylights. Offering additional durability over the baseline coating, AAMA 2604 coatings are used in schools, hospitals, and retail stores. They also can be applied to architectural elements that will be highly exposed, such as light posts or flagpoles, and residential, commercial, and industrial fencing. Metal facades, playground equipment, stadium seating, and railings perform well under AAMA 2604 coatings. These south Florida five-year coatings come in low, medium, or high glosses, and some include 10-year warranties. They have good yellowing and storage stability, with less than 5 Delta E change in color. Delta-E (dE) is a single number that represents the 'distance' between two colors, with a Delta-E of 1 being the smallest color difference the human eye can see.

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AAMA 2605 coatings are tested for 10 years in Florida. This finish incorporates the fluoropolymer resin for exceptional durability, colorfastness, and gloss retention. They can include up to 30-year warranties with proven durability and retention of color and gloss. They perform well with resistance against hazards, such as chemical attack and surface damage from acid rain, salt, mortar deposits, humidity, and graffiti. AAMA 2605 powder coatings are the superior architectural finish for highly visible elements, such as windows, doors, and skylights, as well as storefronts, monuments, skyscrapers, stadiums, and hospitals. They are highly resistant to weather, abrasion, fading, chalking, and discoloration and an excellent solution for coastal applications.

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This graphic gives a recap of the finishes and their south Florida testing duration as well as the resin that is used for each specification. As you can see at the bottom of the graphic, the baseline AAMA 2603 powder coating finish was tested for one year in Florida and consists of the standard durable polyester resin. Next up comes AAMA 2604 powder coating made with a super durable polyester resin and tested for five years at the outdoor laboratory. Finally, at the top is the superior AAMA 2605 powder coating tested for 10 years and made of the highly durable fluoropolymer resin. The resin used in the AAMA 2605 finish creates a carbon/fluorine bond, one of the strongest molecular bonds. It is the most durable architectural coating available.

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For building professionals, it can be a challenge to decide whether to incorporate AAMA 2604 powder coatings, which provide reasonable durability and weathering capacity, or to go for the superior and more expensive AAMA 2605 finishes. While AAMA 2605 coatings can be used beautifully for windows, doors, skylights, and commercial storefronts, so can AAMA 2604 coatings. For curtain walls, high-value structures or monuments, and seacoast environments, it is worthwhile to consider the AAMA 2605 specified coatings. Building professionals have to consider the long-term needs, such as cosmetic and structural protection, along with the relative exposure of an area to weathering and hazards.

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Overall, powder coatings provide a wide range of options for both interior and exterior architectural applications . Lacking VOC emissions, harmful vapors, or hazardous waste products, powder coatings bring benefits that improve the quality of life for building professionals and occupants. Easy application of powder coatings will result in quick training for operators. Low-cure technology conserves energy. And powder coatings are efficient and safe to clean up. Generally, they are applied with one coat, and they cure and dry quickly. Powder coatings are divided into three AAMA specifications for the ease of decision making by building professionals and clients.

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The powder-coating finish is environmentally safe with green finishing technology. As a result, it can contribute toward LEED credits in a building project. Powder coatings are tougher and more durable than liquid finishes. They also offer better chemical and weather resistance than liquid finishes and present a wider selection of colors, glosses, and textures. Less damage occurs during manufacturing and shipping to powder-coated products. Also installation is more reliable in terms of avoiding damaging the powder coating. But in the end, the efficiency, ease of installation, and lack of VOC emissions and hazardous waste provide two solid reasons to choose powder coatings.

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