The effects of Zn segregation and microstructure length scale on the corrosion behavior of a directionally solidified Mg-25 wt.%Zn alloy

• Published in: Journal of alloys and compounds 2017-11, Vol.723, p.649-660
• Main Authors: Verissimo, Nathalia C., Freitas, Emmanuelle S., Cheung, Noé, Garcia, Amauri, Osório, Wislei R.
• Format: Article
• Language: English
• Subjects: Alloys; Biodegradability; Biodegradable materials; Biomedical materials; Corrosion currents; Corrosion effects; Corrosion resistant alloys; Directional solidification; Electrochemical analysis; Electrochemical corrosion; Equivalent circuits; Impedance; Magnesium base alloys; Mg-Zn alloys; Microstructure; Polarization; Scale (corrosion); Solidification; Studies; Surgical implants; Transplants & implants; Zinc base alloys
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2017.06.199

Biodegradable implants can be used in order to avoid removal surgery. Mg-Zn alloys are considered interesting alternatives for biomedical applications, however, studies concerning the effects of microstructural features in the as-solidified condition and segregation aspects on the resulting electrochemical behavior are scarce. This investigation is focused on the evaluation of the electrochemical corrosion of an as-solidified Mg-25 wt.% Zn alloy in a 0.15 M NaCl solution at 25 °C. EIS plots, potentiodynamic polarization curves and equivalent circuits are used. It is shown that Zn segregation affects both the galvanic couple and the cathode-to-anode area ratio. It was found that finer and homogeneously distributed Mg-rich six-fold branched equiaxed dendritic grains induce lower corrosion current density and higher polarization resistance when compared with equivalent results of coarser ones. •Zn segregation affects the galvanic couple formed by the Mg-rich/eutectic phases.•Finer dendritic grains shown lower corrosion current density and higher polarization resistance.•Coarser microstructure induces to osseointegration in implantation due to microcavities.