Coil Anodized Aluminum Myths: Durability

Busting myths about coil anodized aluminum

Engineers, architects, and designers need to rely on materials that last, but the true durability of coil anodized aluminum can be obscured by misconceptions. This blog is part of a series addressing those myths to give you the information you need to evaluate coil anodized aluminum as a material for your next project.

Myth: Anodized aluminum is a coating.

In fact, anodized aluminum is not coated, but rather the outside layer of the metal itself has undergone an electrochemical process. This process grows the aluminum oxide layer from the base aluminum, bonding at the molecular level, so it cannot chalk, chip, flake or peel like coatings or paint. The aluminum oxide layer is actually part of the aluminum!

Coatings, on the other hand, are a separate material either sprayed or roll coated onto the aluminum. Additionally, coatings often require a separate primer or adhesion promoter to help the material stick to the aluminum.

Myth: Anodized aluminum does not last as long and is not as durable as coatings like paint.

Anodized aluminum is more durable and lasts longer than most coatings. Aluminum Oxide is part of the Corundum family of gemstones, like a sapphire, and is second only to diamonds in terms of hardness. The hardness of the anodic layer formed in the anodizing process described above makes it very abrasion resistant, outperforming paint in Tabor abrasion and pencil hardness tests. This superior hardness and abrasion-resistance leads to a more durable product.

Paint, on the other hand, does not improve the abrasion resistance of aluminum, but instead hinders it. Because paint is a coating that is either rolled or sprayed onto the base aluminum, it relies on the surface tension it creates with the metal, or a primer, for adhesion. This surface tension can break down over time, causing the paint to lose adhesion, leading to chalking, chipping, flaking and peeling. This loss of adhesion can creep over time, causing more and more of the surface area to lose its paint. Once such paint loss occurs in architectural exterior applications, replacement of the material may be required instead of repainting due to the high costs of labor to sand blast and repaint the original surface.

With anodized aluminum, if the anodic layer is somehow breached all the way to the raw aluminum underneath, the aluminum will self-heal by creating its own protective oxide layer. This self-healing ensures that any damage will not creep beyond the initial damage point, thus mitigating the need for costly repairs. The anodic layer also resists graffiti and is easy and safe to clean.

Check back to learn how coil anodized aluminum performs in coastal applications, and what warranties are available for coil anodized solutions.

Architecture Guide to Aluminum CTA image