Effect of tensile cracks on the corrosion protection properties of anodic oxide films on 5083 Al alloy

Sulphuric Acid Anodic Oxide (AAO) film is a common method for corrosion protection of 5083 Al alloys, and cracks may occur in the AAO film due to stress damage. In this study, cracks in the AAO film on 5083 Al alloy were pre-prepared by mechanical tension, and the cracks on the corrosion protection property of AAO film were in -situ investigated by scanning electrochemical microscopy (SECM). The morphology and composition of the AAO film were measured by SEM, XRD and XPS. The results show that the corrosion protection performance of AAO film for 5083 Al alloy decreases with the increase of cracks, which is due to the fact that cracks can act as diffusion channels for corrosive media, resulting in serious corrosion reaction. SECM shows the local current at the cracks of the AAO film first increases and then decreases due to the cracks being gradually repaired by the deposited corrosion products (Al(OH) 3 , Al(OH) 2 Cl, and AlOOH). A repair mechanism of cracks in AAO film on 5083 Al alloys is revealed during the corrosion process.