Improving Corrosion Resistance of AZ31 Alloy using Zr/Si Sol–Gel Coating in Simulated Body Fluid

Recent advances in biomedical engineering have highlighted the potential of biocompatible metals, particularly magnesium alloys, for temporary implant applications. These materials are designed to degrade in physiological environments, eliminating the need for secondary surgical removal. However, their corrosion rate often exceeds the rate of tissue healing, limiting clinical applicability and requiring effective strategies to better control degradation [1].

This study presents the development of a Zr–Si hybrid sol–gel coating aimed at enhancing corrosion resistance and regulating the degradation behaviour of AZ31 magnesium alloy. The coatings were synthesised from tetraethyl orthosilicate (TEOS) and the organically modified silane 3-methacryloxypropyltrimethoxysilane (MAPTMS). Zirconium(IV) propoxide (ZTP), chelated with methacrylic acid (MAA), was incorporated to tailor the inorganic–organic network structure and optimise protective performance [2]. The evolution of the sol–gel system was monitored by in situ Fourier transform infrared spectroscopy (FTIR), while surface morphology and elemental composition were characterised using scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM/EDS).

Corrosion performance was evaluated in simulated body fluid (SBF) using potentiodynamic polarisation and electrochemical impedance spectroscopy. Degradation kinetics in SBF were further assessed by hydrogen evolution during immersion.

The developed hybrid coatings improved corrosion resistance and effectively moderated magnesium degradation in simulated physiological conditions, demonstrating the potential of Zr–Si hybrid sol–gel systems for controlled resorption of magnesium-based implants.

References
[1] L. Xu et al., Materials 15 (2022) 2613. https://doi.org/10.3390/ma15072613.
[2] P. Rodič et al., Prog. Org. Coat. 124 (2018) 286–295. https://doi.org/10.1016/j.porgcoat.2018.02.025.

Acknowledgements
This work was supported by the Slovenian Research and Innovation Agency (ARIS) under research core funding P1-0134, P2-0393, P2-0089, and P2-0223, and through project J2-60047