THE IN-HOUSE POWDER-COATING PROCESS

More companies are specifying powder coatings both for the purpose of a more durable material and as a way to express a building's unique personality.

Powder coating is a dry finishing process that has become extremely popular since its introduction in North America back in the 1960s. Representing more than 15 percent 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 both 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 Does Powder Coating Work?

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 the aluminum 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. Sometimes a powder coating is applied during a fluidized bed application. Preheated parts are dipped in a hopper of fluidizing powder, and the coating melts and flows out on the part. Post cure may be needed depending on the mass and temperature of the part and the type of powder used. No matter which application process is utilized, powder coatings are easy to use, environmentally friendly, cost-effective, and tough.

What Is a Powder Coating Oven?

Powder coating ovens heat up powder-coated parts to bake the powder on them. They can be electric heated or gas fired and are most commonly batch-style ovens, where one load of parts at a time is placed into the oven and heated. For high-volume part baking, powder-coating ovens can be continuous, where the parts are carried through the oven on a conveyor.

What Are the Benefits of Powder Coating?

Powder coating offers a very durable and attractive coating. It is also environmentally friendly, as no solvent fumes are released, and overspray is kept to a minimum due to the electrostatic attraction of the powder to the substrate.

What Is the Durability of Powder Coating?

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

Powder-Coating Process

• First, the extruded aluminum is pre-treated to remove dirt, oil lubricant, metal oxides, welding scale, and other coating. This process happens in multiple stages and often involves rinses, etching, and degreasing cycles until the surface is ready.
• Second, finely ground particles of pigment and resin are sprayed onto the extruded aluminum to coat it. These charged particles adhere to the electrically grounded surfaces of the aluminum.
• Next, the coated product is heated inside the curing oven at around 356 degrees Fahrenheit for 18 to 19 minutes. When the thermosetting powder is exposed to heat, it begins to melt and flow. The chemical reaction creates a high molecular weighted structure on the surface.
• After the extrusions are baked in the oven, they are removed and cooled. Once cooled, the extruded aluminum has a smooth, hardened surface.

EXTRUDED ALUMINUM AS A GREEN SOLUTION

Aluminum lasts a long time before it needs to be replaced, and its lightweight quality and ability to be recycled make it an ideal green building material.

As a green building material, aluminum has a lot going for it. Yes, it is an abundant natural resource, but it is also recyclable, and most aluminum is made from 75–100 percent post-industrial and post-consumer scrap. With characteristics of strength and high durability, products made from aluminum last a long time before they need to be replaced and recycled. And as a lightweight material (at least one-third lighter than other metals), it is less expensive to transport than other metals that are traditionally used for architectural purposes.

All of these attributes mean that aluminum products can help earn LEED v4 certification. Specifically, they can help earn certification in these areas:

• Energy and Atmosphere Credit: Optimize Energy
• Materials and Resources Credit: Building Product Disclosure and Optimization Credit: Environmental Product Declaration (EPD)
• Indoor Environmental Quality Credit: Low-Emitting Materials

There is extensive information available about the qualities of extruded aluminum and the ways in which it meets or exceeds green standards.

Extruded aluminum is listed as compliant with regulatory thresholds in regard to water, air, and noise in the environmental product declaration (EPD), which is an independently verified document that offers transparent and comparable information about the life-cycle environmental impact of products in a credible way.

Its sustainable qualities also can be found in mindful MATERIALS, a searchable platform that communicates product transparency in a brand-agnostic manner.

As far as lists go, extruded aluminum cannot be found on The Living Building Challenge (LBC) Red List—which is a good thing. The Red List represents the “worst-in-class” materials, chemicals, and elements known to pose serious risks to both human health and the environment.

Finally, aluminum is the only material that more than pays for the cost of its own collection. As a 100-percent recyclable material, recycled aluminum saves more than 90 percent of the energy costs needed for primary production, and it generates only 8 percent of the emissions. Once the material is produced, it can be recycled indefinitely. As an interesting side note, approximately 75 percent of all aluminum ever produced is still used today.