A cross‐sectional TEM study of corrosion initiation in rapidly solidified Mg‐based ribbons

Abstract

Abstract The microstructures across the whole thickness of uncorroded and corroded rapidly solidifed Mg and Mg‐9% Al ribbons have been characterized using TEM cross‐sectional techniques. In this way, differences in susceptibility to and mechanisms of corrosion initiation between four clearly different magnesium alloy microstructures have been observed. These observations demonstrate that corrosion initiation occurs preferentially at grain or cell boundaries in both ‘pure’ magnesium and Mg‐Al ribbons and that aluminium in solid solution clearly improves the corrosion resistance of magnesium alloys. Mg 17 Al 12 precipitates at grain cell boundaries appear to promote corrosion initiation locally, but intragranular Mg 17 Al 12 precipitates do not appear to promote corrosion to the same extent.