The impact of atmospheric conditions on anodized aluminum

Anodized aluminum is well known for its corrosion resistance. It has been used for almost a century in architectural applications. In this application, it is continuously exposed to atmospheric conditions. Consequently, its service-life can be affected by several factors such as specific microclimates, atmospheric corrosion and degradation. In the case of anodized aluminum, the main components of degradation are changes at the aesthetic level such as changes in color and degradation of the properties of the anodic aluminum oxide (AAO) layer. In the case of coating failures, the appearance of corrosion under the anodized coating is common. Degradation of anodized aluminum can also be characterized by loss of thickness of the anodized layer due to exposure to the environment. Depending on the conditions, different rates of thickness loss can be obtained. Additionally, scratches can occur during transport or use of anodized products, leading to the rejection of products or their substitution. In this work, the response of undamaged and lightly damaged anodized aluminum profiles to simulated environmental conditions was assessed by submitting these to accelerated weathering testing, including ultraviolet radiation exposure and particular humidity-temperature conditions based on natural conditions. Additionally, the AAO layer was characterized by scratch testing and optical and scanning electron microscopy.