Formation of stable coral reef-like structures via self-assembly of functionalized polyvinyl alcohol for superior corrosion performance of AZ31 Mg alloy

• Main Authors: Mosab Kaseem, Tassawar Hussain, Sung Hun Baek, Young Gun Ko
• Format: Article
• Language: English
• Published: Elsevier 2020-08-01
• Series: Materials & Design
• Subjects: Self-assembly; Anisotropic growth; Coral reef-like structure; Functionalized polyvinyl alcohol; Corrosion
• Online Access: http://www.sciencedirect.com/science/article/pii/S0264127520303579

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.