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The influence of trace Si on the microstructure and corrosion behavior of as-cast Mg-0.4Mn-xSi (x = 0, 0.02–0.3) alloys is studied. With the presence of trace Si in Mg-0.4Mn alloy, MnSi, Mn 5 Si 3 and Mn 3 Si phases form. The Mn x Si y phase significantly increases the corrosion rate of Mg-Mn-Si alloys due to strong micro-galvanic corrosion between Mn x Si y phases and Mg matrix. During corrosion, the rod-like Mn x Si y precipitates can lead to stronger cathodic activation behavior than the block-like Mn x Si y precipitates since the rod-like Mn x Si y phase is more difficult to detach from Mg matrix, which results in the more exposed area of cathodic sites. The raw/processed data required to reproduce these findings cannot be shared at this time, because the data also forms part of an ongoing study. ● Presence of traces of Si in Mg-Mn alloys could result in formation of Mn x Si y phases. ● Strong micro-galvanic corrosion occurs between Mn x Si y phases and Mg matrix, accelerating corrosion. ● Mn x Si y phase significantly increases the corrosion rate of Mg-Mn-Si alloys. ● Rod-like Mn x Si y precipitates leads to stronger cathodic activation behavior than block-like Mn x Si y precipitates. [ABSTRACT FROM AUTHOR]

Mg-based alloys as revolutionary implantable biomaterials have increasingly attracted considerable attention, owing to their biodegradability in vivo and beneficial effects on biological systems. The degradation process and products of Mg-based alloys have been reported to exhibit significant biological effects on host-tissue responses. However, these effects have not yet been fully understood. This review systemically summarizes and analyses the current understandings and recent research progress in this area. The primary focal points are the biological effects and related mechanisms associated with the degradation behaviour of Mg-based alloys. The biological impacts of the degradation products are elucidated and the arguable or controversial issues are also discussed, providing a pathway toward a greater understanding of the biological implications of Mg-based alloys. Furthermore, based on these biological implications, the restorative potential of Mg-based alloys for applications in tissue repair and regeneration is summarized. Finally, outlooks on biosafety evaluation and design strategies for Mg-based alloy implants are briefly discussed. [ABSTRACT FROM AUTHOR]

The in vitro and in vivo degradation behaviour and biocompatibility of a Mg-Mn-Zn alloy with MAO coating and MAO/PLLA composite coating were studied. The in vitro degradation behaviour was studied by investigating electrochemical behaviour and observing surface morphology for up to 12 weeks and the in vivo degradation behaviour and osteogenic effect were studied by implanting the samples in the mandibles for up to 16 weeks. Both in vitro and in vivo degradation results demonstrated the MAO/PLLA composite coating effectively reduced the degradation rate Mg-Mn-Zn alloy in comparison with MAO coated alloy, while localized degradation was the main degradation form for the coated Mg alloys. In vivo implantation analysis results clearly showed that the MAO/PLLA coated sample exhibited less local osteogenic defects, less bone cavities and less local inflammatory reaction than MAO coated sample. However, more attentions should be paid on the osteogenic defects around the localized corrosion region of the MAO/PLLA coated sample. It was suggested that MAO/PLLA might be an effective coating for the bone implant application of magnesium alloy. • PLLA polymer blocks MAO oxidation hole, hinders charge transfer and slows down corrosion process. • Samples with lower corrosion rate had stronger bone growth promoting ability. • Localized corrosion is the main corrosion form of the MAO/PLLA composite coating samples. • The rapid accumulation of local corrosion products and alkalization led to surrounding cavity bone non-union. • Tightly wrapped bone tissue surrounding the implant protected the erosion of body fluid and delayed the subsequent degradation process. [ABSTRACT FROM AUTHOR]

• Both metallic Ag and Ag oxide exist in the coating. • A nano-sized Ag-rich layer exists at the substrate/coating interface. • PEO affects corrosion morphology and susceptibility of Mg-Ag alloy. • A sustained Ag+ release is achieved after PEO of Mg-Ag alloy. The application of biodegradable Mg alloys as implanted devices has been hindered by their low corrosion resistance and potential risk associated with microbial infection. In the present work, a rolled Mg-Ag alloy was studied, which was subjected to plasma electrolytic oxidation (PEO) to achieve a favoured balance between corrosion resistance and antimicrobial capability. The Ag distribution, corrosion resistance and Ag ionic release behaviour have been examined in details. It is revealed that PEO process leads to both incorporated Ag+ and Ag-rich nanoparticles in forms of metallic Ag and Ag oxide across the coating. In addition, a nano-sized Ag-enriched layer also exists at the substrate/coating interface. The microstructural modification associated with PEO process results in an increased corrosion resistance and a sustained Ag ionic release, indicating that it is a promising surface modification technique for antibacterial Mg-Ag alloy. [Display omitted] [ABSTRACT FROM AUTHOR]