Structural characterisation and degradation of Mg-Li thin films for biodegradable implants

Freestanding thin films of Mg-Li (magnesium-lithium) alloys with a Li mass fraction between 1.6% (m/m) and 9.5% (m/m) were prepared and studied with respect to their structure and degradation properties. With increasing Li content, the microstructure deviates from hexagonal Mg-Li with strict columnar growth and preferred orientation, and additional cubic Mg-Li and Li₂CO₃ occur. The corrosion rate was measured in Hanks' balanced salt solution by potentiodynamic polarisation and weight loss measurements to investigate biodegradation. Influences of the orientation, phase and protective layer formation lead to an increase in corrosion from 1.6 to 5.5% (m/m) from 0.13 ± 0.03 to 0.67 ± 0.29 mm/year when measured by potentiodynamic polarisation but a similar corrosion rate for 9.5% (m/m) and 3% (m/m) of Li of 0.27 ± 0.07 mm/year and 0.26 ± 0.05 mm/year.