The link between microstructure and corrosion of Mg alloy ZE41

Mg alloy ZE41, used extensively in the aerospace industry, possesses excellent mechanical properties albeit poor corrosion resistance. This paper investigates the mechanism of corrosion, and the interaction between the grain boundary intermetallic phases, the Zr-rich regions within the grains and the bulk Mg rich matrix in both the as-cast and heat-treated conditions. The results of optical and scanning electron microscopy (SEM) together with potentiodynamic polarisation have shown the importance of the microstructure in the initiation and propagation of corrosion in an aqueous environment. The Zr-rich regions play a distinct role in the early stages of corrosion in this alloy. It is also shown by altering the Zr distribution by means of heat treatment, that the corrosion morphology and mechanism is changed significantly.