Influence of the Self-Sealing Layer on the Corrosion of Anodic Aluminum Oxide Films

It is well-known that novel structured anodic aluminum oxide films composed of a self-sealing layer, a porous layer, and a barrier layer show much-better anticorrosion performance compared to that of porous anodic aluminum oxide film (AAO). However, the factor that critically influences the anticorrosion performance of anodic aluminum oxide film is still unknown. The relationship between the self-sealing layer structure and the anticorrosion properties of anodic aluminum oxide was explored in the present work. The surface morphology, film thickness, and surface roughness were characterized by field emission scanning electron microscopy and confocal laser scanning microscopy. Electrochemical test results revealed that the anticorrosion property of self-sealing anodic oxide film increased with the thickness of the self-sealing layer instead of the total film thickness alone. The self-sealing layer successfully decreased the diffusion of chlorine ions permeating into the porous layer. The self-sealing layer played a critical role in anticorrosion by inhibiting the ingress of corrosive medium into the porous layer.