Corrosion Behavior of Novel Mg-9Li-7Al-1Sn and Mg-9Li-5Al-3Sn-1Zn Alloys in NaCl Aqueous Solution

Corrosion behavior of two multiphase Mg-Li-Al-based alloys in 0.6 M NaCl aqueous solution is investigated by hydrogen gas evolution measurement and electrochemical test. This paper reports, for the first time, the comparison of hydrogen evolution and Tafel extrapolation results of Mg-Li-Al-based alloys. The corrosion rate of Mg-9Li-7Al-1Sn is observed to be reasonably higher when compared to that of Mg-9Li5Al-3Sn-1Zn, and both the alloys have shown higher corrosion rate than that of Mg-3Al-1Zn alloy (AZ31B). The micro-galvanic corrosion of primary precipitates and hcp a-phase (Mg-rich) is not as severe as was observed in case of the secondary precipitates and bcc b-phase (Li-rich). Corrosion mechanism of multiphase Mg-Li-Al-based alloys in chloride solution, which has not been adequately reported in the literature, is lucidly articulated based on the early stages of corrosion, film morphology, and in situ hydrogen bubble study.