Influence of aluminium enrichment in the near-surface region of commercial twin-roll cast AZ31 alloys on their corrosion behaviour

The effect of increasing the Al concentration to a value between 0.5 and 0.8 wt.% within the 10-μm thick surface layer of a commercial AZ31 alloy sheet manufactured by twin-cast rolling method on its corrosion behaviour was investigated. In long term exposure, both the uniformity of the double layered Mg-Al hydroxide (LDH) formed in the inner layer of the corrosion product on the aluminium-rich surface AZ31 specimen and the precipitation of a significant amount of aluminium hydroxide contributed to enhancing the corrosion resistance significantly.