| Summary: | The development of novel structures having high surface areas and unique functional and electrochemical properties, is of high interest as a way to expand the applications of magnesium-based materials. Herein, we discussed the growth mechanism of coral reefs-like structures on the surface of defective layer made by plasma electrolysis (PE) of AZ31 Mg alloy. The PE layer was immersed in a solution containing polyvinyl alcohol (PVA), phosphoric acid (H3PO4) and aluminum phosphate (AlPO4) at ~85 °C under stirring condition, and the results were compared to the case when PE layer was immersed in a solution composed only of partially phosphorylated PVA (PPVA). A detailed examination of the morphology of PE layer immersed in a solution with AlPO4 suggested that the formation of coral reefs-like structure would occur through a mechanism involving an anisotropic growth of PPVA-AlPO4 complex composite. It was confirmed that PPVA-AlPO4 has stronger affinity than PPVA to react with Mg2+ ions through coordination covalent bonding due to the presence of additional PO43− group. The coral reef-like structures effectively delayed the corrosion of Mg alloy substrate, resulting in superior corrosion protection properties. The shape-controlled synthesis of coral reef-like structures provided a green approach desirable for electrochemical applications of magnesium-based alloys.
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