Influence of manufacturing route and surface modification on the corrosion behavior of WE43 Mg and Zn1Mg bioabsorbable metallic alloys

Abstract

The use of biometals is becoming more and more popular thanks to the development of new alloys that take advantage of their biodegradability. Due to this beneficial property, particularly Magnesium (Mg) and Zinc (Zn) have been studied frequently within the currently applicable group of bioabsorbable metals. This investigation studied the microstructure, and electrochemical behavior of WE43 and Zn1Mg alloys manufactured by extrusion and Laser Powder Bed Fusion (LPBF), with and without plasma electrolytic oxidation (PEO) surface treatment. The extruded WE43 showed a corrosion rate of 3.42 ± 0.10 mm/year, while the LPBF counterpart has an increased corrosion rate of 11.85 ± 0.14 mm/year. This increase was explained via yttrium oxide particles found in the LPBF material that decrease the protective effect of the corrosion layer, and hence reduce corrosion resistance. For the Zn1Mg, the extruded sample had a corrosion rate of 0.98 ± 0.41 mm/year, whereas the LPBF sample also showed a higher corrosion rate of 2.70 ± 0.09 mm/year. This result was explained by a higher volume fraction of second phase eutectic structure in the LPBF samples, which increased the microgalvanic corrosion between Zn grains and MgZn structures in the eutectic phase. The extruded samples showed thicker PEO oxide layer in both the WE43 and Zn1Mg materials than the LPBF-fabrication samples, and in all cases the corrosion resistance was improved when applying these surface treatments. These findings highlight the impact of evaluating the influence of different manufacturing methods and PEO surface treatments on the corrosion resistance and durability of these biomedical alloys.