Influence of Exposure Conditions and Particulate Deposition on Anodized Aluminum Corrosion

Abstract

Anodizing is commonly used for corrosion protection of aluminum and its alloys in the construction industry. The anodic aluminum oxide (AAO) coating has a high ability to prevent the development of extensive pitting corrosion in aluminum substrates, particularly in marine sites, as was observed during a 10-year atmospheric corrosion study carried out in several marine and industrial sites. However, this study also evidenced that this coating can be highly affected by the deposition of particulate material in industrial polluted environments, sometimes in unexpected ways. This study presents information on the atmospheric corrosion of anodized aluminum exposed at two different chemical industrial complexes: a fertilizer production plant and a pulp and paper mill. Visual assessment of surface changes, pitting depth and mass variation with exposure were determined to quantify the degradation suffered. Additionally, SEM/EDS analyses were carried out on the exposed surfaces. Based on the results obtained, the role played by the deposition of airborne particles present in the two environments with respect to the type and level of damage observed is discussed. Deposits of roasted pyrite ash and phosphates or of wood chips and lime particles enhanced pitting corrosion or caused dissolution of the AAO coating.

The effect of time and heat exposure on the wettability and glossiness of CAA and FPL coatings for aluminum substrates

“…The primary reason for the increase in contact angle could be the greater absorption of atmospheric and environmental contaminants by the coatings. Deposition of pollutants on the surface saturates the surface and blocks intercellular cavities, particularly in the anodized structure [26]. While the micrometer and nano-size holes can enhance wettability, the presence of environmental contamination has resulted in a reduction of the coats' wettability.…”