Influence of anodizing processes on corrosion performance of AA5005 aluminium alloy

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Résumé

To investigate the effects of anodizing processes on the corrosion performance of alloy AA5005, a series of electrochemical and salt spray tests was conducted. Test results showed that the corrosion performance of anodized AA5005 depends both on anodizing time and the sealing process. Scanning electron microscopic (SEM) examination revealed multi-site crack initiation for the pickled and anodized specimens. Three salt spray testing methods: neutral salt spray testing, acetic salt spray testing, and prohesion testing were performed simultaneously with electrochemical impedance spectroscopy and optical microscopy to evaluate long-time corrosion performance of the anodic oxide layer. It is found that salt spray and immersion testing provide similar results for the hydrothermally sealed oxides, but differ substantially for the cerium-treated oxides. The discrepancy is because the continuously refreshing electrolyte layer during salt-spray testing promotes film dissolution and hinders precipitation of aluminium hydroxide and cerium compounds, unlike in stagnant bulk electrolyte.

Mots-clés

Alumium, Anodization, Corrosion, Electrochemical Testing, Salt spray.