Ace the Anodizing Process

How Safe Is Minimizing Color Variation, Rack Marks, and Ensuring Industry-Best Anodizing Practices?

Anodizing aluminum materials and components is an entirely different process when compared to other methods of colorization or finishing for architectural products. Unlike paints or powder-coatings, anodizing actually interacts with the chemistry of the metal, which means delivering exact, consistent colors can present a challenge.

Components being anodized also must be fixed, or racked, to be held in place so that they can be submerged into the anodizing tank. Depending on the component’s size and shape, the process can leave behind unwanted rack marks that are visible once the anodizing process is complete.

That being said, the benefits of anodizing for the architecture industry cannot be overstated.

Anodized aluminum components are abrasion-resistant, durable, heat-resistant, non-toxic, and offer superior corrosion resistance. That is why architects around the world choose anodizing, and many of them are relying on SAF to provide industry-leading service and high-quality anodized products.

It starts by setting and maintaining a standard.

Curtail Color Variation

Anodized aluminum is a natural finish similar to that of copper, stainless steel, wood, or brass. Properly anodized aluminum does not deliver color uniformity, instead offering natural variations in color, gloss, texture, and overall appearance to give it an authentic look.

Color difference in aluminum anodizing may be measured by Delta E (dE), which is a metric used to determine how and to what degree the human eye perceives color difference. The American Architectural Manufacturers Association (AAMA) allows for a 5 Delta E color variance in anodized materials, a standard that SAF is committed to meeting within the same run or batch of anodized product.

“One of the most important pieces of equipment we use is a spectrocolorimeter, or an electronic color measuring device,” said George Allan, key account manager at SAF. “It takes just seconds for the device to tell us whether or not the anodized component is within spec. If it registers as a fail on our device, we start over.”

However, the anodizing process itself is not the only factor that can contribute to color variance. The metal used, its composition, its surface characteristics, and its temper all play a significant role in the outcome.

“We buy anodizing-quality aluminum from only three or four different mills and metal for extrusions from just a handful as well,” Allan added. “Because we stick with the same handful of suppliers, we can provide a much greater degree of consistency in the final product.”

This is important because not all aluminum is the same. Different product types (e.g. extrusions, sheet, plate, castings, forgings, etc.) are made up of different alloys. In addition, different lots of metal may have different material compositions. The best way to ensure color uniformity and a predictable final product is for architects to find an anodizer that consistently purchases from the same providers.

Reducing Rack Marks

To anodize aluminum, the component must be securely racked before being submerged into the tank. This racking contact point is the conduit for the electrical current that creates the anodic coating. Component type, size, and the anodic coating required determine the best racking method.

“SAF is always coming up with better ways to rack aluminum for anodizing,” Allan explained. “Our most common method is bolt racking, which typically minimizes visible rack marks as much as possible, but racking method is ultimately determined by product type and size.”

Bolt racking is just as the name suggests. A component is fixed in place by a flat metal arm on one side, and a bolt screwed tightly against the other. The visible rack mark is only as large as the flat end of the bolt, which is typically minimal.

SAF also offers tube racking for rounded tube components. The connection point occurs within the tube, putting pressure on the material from the inside to hold it tightly in position. Tube racking completely hides the rack marks because the connection point is on the inside instead of the exposed exterior.

SAF offers many other racking methods. The best fit ultimately determines the technique used for an anodized component.

Why Anodizing?

Specifying anodized aluminum has myriad benefits for buildings and building owners.

The foremost advantages are durability and abrasion resistance. Especially relevant for exterior applications, anodized products have an extremely long lifespan and offer economic advantages due to ease of (or lack of required) maintenance.

Anodizing is a reacted finish, so the degree to which the finish adheres to the metal far exceeds that of paints or other applied finishes. Unique to anodizing, the process allows the metal to maintain the authentic metallic appearance of aluminum as well.

Anodized aluminum’s sheen and metallic appearance are preserved even after long-term exposure to UV rays. In addition, anodized architectural components do not chip or peel.

Maintenance is a breeze, too. According to the Aluminum Anodizers Council, “Scars and wear from fabrication, handling, installation, frequent surface dirt cleaning, and usage are virtually non-existent. Rinsing or mild soap and water cleaning usually will restore an anodized surface to its original appearance.”

The Final Say

Architects, contractors, and owners specify anodized aluminum for various applications ranging from exterior facade panels and column covers to interior ceiling systems, wall panels, and much more.

Regardless of application, components made of anodized aluminum provide increased durability and a genuine metallic finish. SAF offers more colors than the traditional range of champagne through dark bronze, too, so architects can select bright, bold colors in an acid etch (matte finish) or caustic etch (shinier finish) to meet their design goals.

Architects, contractors, and building owners always strive to strike a balance of performance and aesthetics during product selection, and usually for the same reasons. All stakeholders want products that make their buildings visually appealing while simultaneously providing durability and longevity.

With an emphasis on reducing rack marks, always working with a small group of trusted metal suppliers, and constantly ensuring customer satisfaction, SAF maintains its steadfast commitment to providing the construction industry’s highest quality anodized architectural components.

For more information on custom anodizing and how to specify, visit: Custom Anodizing