PMMA–Siloxane–Silica Coating to Enhance Corrosion Resistance of AZ31

Several studies in biomedicine have demonstrated the advantages of biodegradable and biocompatible metals for temporary implants, as they naturally degrade within the body, eliminating the need for surgical removal. Among them, magnesium–aluminium–zinc alloys, such as AZ31, show potential for controlled degradation in physiological environments, but their primary limitation is their rapid degradation.[1] This accelerated corrosion compromises implant integrity, leading to premature failure and limiting clinical applications. Thus, effective protective strategies are essential to enhance their corrosion resistance.

This study aimed to (a) perform a surface pretreatment to improve adhesion between the protective coating and the AZ31 alloy, and (b) develop a PMMA–siloxane–silica coating to reduce degradation. The formulation, based on 3-(methacryloyloxy)propyl trimethoxysilane and methyl methacrylate, was optimized for enhanced protective properties[2]. Its synthesis was characterized using real-time Fourier transform infrared spectroscopy, while its surface morphology and composition were analyzed via scanning electron microscopy and energy-dispersive spectroscopy. Corrosion resistance was evaluated through immersion tests in simulated body fluid (SBF) using potentiodynamic polarization and electrochemical impedance spectroscopy. Additionally, degradation behaviour was evaluated by monitoring pH variations and hydrogen evolution in SBF over time.

The results confirm that the PMMA–siloxane–silica coating significantly enhanced AZ31 corrosion resistance, ensuring controlled degradation. These findings present the potential of siloxane–silica coatings for biomedical applications.

References:

[1] M. He, L. Chen, M. Yin, et al., Review on magnesium and magnesium-based alloys as biomaterials for bone immobilization, J. Mater. Res. Technol. 23 (2023) 4396–4419. https://doi.org/10.1016/j.jmrt.2023.02.037.

[2] P. Rodič, B. Kapun, I. Milošev, Durable Polyacrylic/Siloxane-Silica Coating for the Protection of Cast AlSi7Mg0.3 Alloy against Corrosion in Chloride Solution, Polymers 15 (2023) 3993. https://doi.org/10.3390/polym15193993.

Acknowledgements:

Financial support was provided by the Slovenian Research and Innovation Agency (ARIS) under research core funding P1-0134, P2-0393 and P2-0089 and through the ARIS project J2-60047.