Degradation of sealing layer in anodized aluminium profiles

Abstract

AbstractAnodizing of aluminium is a process for the reinforcement of the natural formation in contact with the atmosphere of a stable and protective aluminium oxide layer. Through this process it is possible to obtain anodic films with a porous external layer that allows be colored. The next step is sealing, in which a gelatinous substance is formed, mainly composed by bohemite. This substance blocks the pores and the surface aspect conservation and corrosion resistance are improved. In this work the causes of degradation of sealing layer in anodized aluminium pieces are studied by means of SEM and EDS. This degradation is independent of the atmosphere in which the material is exposed. It is concluded that photodegradation of an organic additive added in excess in sealing operation is the main cause.