The effects of microstructural factors on the corrosion behaviour of Mg-5Sn-xZn (x = 1, 3 wt%) extrusions

The effects of microstructural factors, including fraction of second phase particles and solute content in a matrix, on the corrosion behaviour of Mg-5Sn-xZn (x = 1, 3 wt%) alloys were evaluated by using potentiodynamic polarisation and immersion tests. The hydrogen evolution rate and the corrosion potential increased with increasing Zn content, while the passive current density decreased. The average corrosion rate measured by immersion test increased with increasing Zn content, and was consistent with the hydrogen evolution rate. The increase of the corrosion rate with increasing Zn content resulted from increasing fraction of Mg2Sn particles and Zn content dissolved in the matrix.