Eco-Friendly Anodizing

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APRIL 2018

ECO-FRIENDLY ANODIZING

Aluminum is the ideal material for use in the production of curtainwall and windows. It is non-magnetic, lightweight, durable, and highly resistant to corrosion. When aluminum is exposed to oxygen in the atmosphere, it forms a natural, thin, aluminum oxide layer on the surface of the metal. This layer helps to protect the underlying aluminum from corrosive agents. To improve and control the properties of the aluminum oxide layer, architectural metal finishing companies put the raw material through a coating process known as anodizing.

Anodizing is the process of electrochemically controlling, accelerating and enhancing oxidation of an aluminum substrate. The anodizing process produces an oxide film that is an integral part of the substrate. It is uniform, hard and protects the rest of the aluminum substrate from deterioration. This provides excellent wear and abrasion resistance with minimal maintenance in most environments.

The coating produced is extremely durable, and the hardness of the surface is comparable to a sapphire—the second hardest substance on earth. This characteristic makes anodize an excellent choice for use in high-traffic areas where resistance properties are important.

Anodized aluminum resists the ravages of time, temperature, corrosion, humidity and warping, adding to its long life cycle. Anodized aluminum is an inert material that is not combustible, 100% recyclable and poses no health risks.

Wausau’s extrusion and formed aluminum components are eco-friendly acid etched by its finishing partner, Linetec. In addition to its environmentally responsible process, the eco-friendly etch delivers not only durable protection, but also an architecturally appealing, matte appearance.

PREPARATION

Before aluminum goes through the anodizing tanks, provisions must first be made to clean and prepare the material to ensure the best finish possible. Materials may exhibit some minor scratches or other imperfections from the extrusion or rolling processes. Eco-friendly anodizing helps conceal these small marks better than conventional anodizing.

Eco-friendly etch anodizing is not only more efficient than conventional etch anodizing, but also minimizes waste. Eco-friendly etch removes 75% to 80% less material and the associated byproducts are recyclable.

PROCESS

The etch process is designed to dissolve a thin layer on the surface of the aluminum to develop a smooth, uniform finish. The typical anodizing employed in the architectural industry is called two-step electrolytic.” The actual anodizing and coloring of the aluminum occur in separate steps of the process.

Step One

The anodizing step takes place in a tank that contains a solution of sulfuric acid and water. The tank is charged with electrical current, and aluminum oxide is formed on the surface of the aluminum.

Step Two

After anodizing is complete, the parts can be immersed in an optional coloring tank, to achieve bronze or black tones instead of the standard clear or silver finish. In the coloring tank, the anodized aluminum is immersed in a bath containing an inorganic metal such as tin, cobalt or nickel, which are deposited in the anodic pores by means of electrolytic current. The amount of time the part is immersed will determine the color achieved. Extending the immersion time and increasing metal deposition create darker colors. The colors typically seen on architectural products range from champagne to dark bronze and black, or even copper.

RESULTS

Anodic finishes on all Wausau’s aluminum products are Class I and suitable for exterior use in architectural projects. They meet or exceed the American Architectural Manufacturers Association’s AAMA 611 “Voluntary Specification for Anodized Architectural Aluminum.”

Class I anodize, with a minimum mill thickness of 0.7 (18 microns), can be a suitable choice for coastal climates, as it possesses exceptional resistance to corrosion, discoloration and wear. Anodize protects and maintains the structural integrity of the aluminum, and ensures a long-lasting, durable finish.

To discuss anodic coating and color details, Wausau’s market managers are available as architectural support resources, and can be reached at info@wausauwindow.com.