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Robust pH-responsive self-healing coating for magnesium alloys
A new double-layered coating system demonstrates how the synergy of tannic acid and cerium ions can significantly enhance the corrosion resistance of magnesium alloys.
Magnesium alloys are lightweight materials with wide industrial potential, but they are highly susceptible to corrosion. A research team in China has now developed an innovative pH-responsive self-healing coating based on a double-layer structure. The underlying layer is a phytic acid conversion film, which not only enhances adhesion but also serves as a reservoir for cerium ions. On top, an epoxy coating incorporates tannic acid-loaded mesoporous silica particles, further encapsulated with chitosan.
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Synergistic effects for long-term corrosion resistance
The combined action of tannic acid and cerium ions provides robust self-healing functionality. The phytic acid pretreatment nearly doubles the adhesion strength to 8.32 MPa, while the controlled release of tannic acid ensures pH-responsive activity. Long-term immersion tests revealed a low-frequency impedance modulus of 9.94 × 10¹⁰ Ω·cm² after 60 days – two orders of magnitude higher than that of a standard epoxy coating. The results highlight a promising strategy for improving corrosion protection of magnesium alloys in demanding environments.
Source: Wan, J. et al., Robust pH-responsive double-layered self-healing coating with synergistic effects of tannic acid and Ce ions applied on Mg alloy via the phytic acid pretreatment. Prog. Org. Coat. 203, 109152 (2025).
