Abstract:

Mg-Li based alloys, being the lightest alloys, are attractive for aerospace applications. We have optimized Li content as 8 wt% and Zn content as 2 wt% in Mg to obtain tensile properties better than the existing commercial and experimental wrought Mg-Li based alloys, which has been discussed in another paper. In the present manuscript, we present the electrochemical corrosion behavior of these two cold-rolled alloys, i.e., Mg-8Li (LZ80) and Mg-8Li-2Zn (LZ82), by open circuit potential evolution, electrochemical impedance spectroscopy and potentiodynamic polarization test in 0.5 wt% NaCl solution. The microstructure of the alloys was examined by scanning electron microscopy before and after corrosion tests in order to explain the observed corrosion behavior. It was observed that LZ82 alloy exhibits better corrosion resistance than LZ80 alloy. Both the alloys exhibited localized pitting corrosion, but it was less severe in the case of LZ82 alloy. The pitting corrosion initiated at the interface of ?-hcp and ?-bcc phases due to micro-galvanic coupling between the two phases, and Zn addition lowered the potential difference between these phases, as revealed by scanning Kelvin probe force microscopy.

Keywords: Mg-Li alloys, Electrochemical corrosion, Electrochemical impedance spectroscopy, Potentiodynamic polarization, Scanning electron microscopy, Scanning Kelvin probe force microscopy

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Prof. Satyam Suwas