In vitro degradation of MAO/PLA coating on Mg--1.21Li--1.12Ca--1.0Y alloy

Abstract

Magnesium and its alloys are promising biomaterials due to their biocompatibility and osteoinduction. The plasticity and corrosion resistance of commercial magnesium alloys cannot meet the requirements for degradable biomaterials completely at present. Particularly, the alkalinity in the microenvironment surrounding the implants, resulting from the degradation, arouses a major concern. Micro-arc oxidation (MAO) and poly(lactic acid) (PLA) composite (MAO/PLA) coating on biomedical Mg--1.21Li--1.12Ca--1.0Y alloy was prepared to manipulate the pH variation in an appropriate range. Surface morphologies were discerned using SEM and EMPA. And corrosion resistance was evaluated via electrochemical polarization and impedance and hydrogen volumetric method. The results demonstrated that the MAO coating predominantly consisted of MgO, Mg₂SiO₄ and Y₂O₃. The composite coating markedly improved the corrosion resistance of the alloy. The rise in solution pH for the MAO/PLA coating was tailored to a favorable range of 7.5--7.8. The neutralization caused by the alkalinity of MAO and Mg substrate and acidification of PLA was probed. The result designates that MAO/PLA composite coating on Mg--1.21Li--1.12Ca--1.0Y alloys may be a promising biomedical coating.

Key words： magnesium alloy; micro-arc oxidation (MAO); poly(lactic acid) (PLA); biomaterial; degradation

Acknowledgements

This research was financially supported by the National Natural Science Foundation of China (Grant No. 51241001), the Natural Science Foundation of Shandong Province (ZR2011EMM004), SDUST Research Fund (2014TDJH104), Joint Innovative Center for Safe and Effective Mining Technology and Equipment of Coal Resources, and Shandong Province as well as Taishan Scholarship Project of Shandong Province (TS20110828).

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