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<p>Biodegradable magnesium (Mg) alloys have been widely considered for orthopedic implantation; yet persistent challenge of excessively rapid degradation in physiological environments hinder clinical application. In this study, an Fe<sub>78</sub>Si<sub>9</sub>B<sub>13</sub> amorphous coating (Fe<sup>AC</sup>) was fabricated on ZK60A alloy via high-velocity oxygen fuel (HVOF) spraying to regulate degradation kinetics while enhancing bioactivity. The Fe<sup>AC</sup> exhibited a dense and homogeneous architecture with a thickness of approximately 170.03&#xa0;μm, an ultralow porosity of 0.95%, and a high amorphous phase fraction of 76.19%. The surface hardness reached 808&#xa0;HV<sub>0.2</sub>, nearly an order of magnitude higher than that of the ZK60A substrate. Electrochemical and immersion tests demonstrated that the coating dramatically reduced the degradation rate to 0.024&#xa0;mm/year, which is 116.6&#xa0;times lower than that of the ZK60A substrate (2.798&#xa0;mm/year). This significant improvement is attributed to a dual-passivation mechanism. On the one hand, a dense Fe<sub>2</sub>O<sub>3</sub>/SiO<sub>2</sub> enriched layer formed on the coating surface effectively suppressed chloride ion attack and charge transfer. On the other hand, the Si<sup>4+</sup> and B<sup>3+</sup> ions released during coating degradation promoted the formation of a secondary protective film. More importantly, the Si-OH and Fe-OH functional groups on the Fe<sup>AC</sup> surface chemically anchored Ca<sup>2+</sup> and PO<sub>4</sub><sup>3−</sup> ions, thereby inducing the formation of a hydroxyapatite layer (Ca/P = 1.65) within 9&#xa0;days, indicating strong potential for osteogenesis. Collectively, these findings demonstrated that the Fe<sup>AC</sup> synergistically enhanced corrosion resistance and bioactivity, providing a highly promising surface modification strategy for Mg-based orthopedic implants.</p> Graphical Abstract <p></p>

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Dual Passivation Mechanism and In Vitro Degradation Behavior of HVOF-Sprayed Fe-Based Amorphous Coatings on Magnesium Alloy

  • 期刊论文

  • 发表日期：

    2026年5月7日

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  • Xiangyun Zhang,
  • Guang Xu,
  • Danqiang Huang,
  • Zhuang Qian,
  • Peng He,
  • Peiqing La,
  • Wenbo Li,
  • Yingchun Xie

摘要

Biodegradable magnesium (Mg) alloys have been widely considered for orthopedic implantation; yet persistent challenge of excessively rapid degradation in physiological environments hinder clinical application. In this study, an Fe78Si9B13 amorphous coating (FeAC) was fabricated on ZK60A alloy via high-velocity oxygen fuel (HVOF) spraying to regulate degradation kinetics while enhancing bioactivity. The FeAC exhibited a dense and homogeneous architecture with a thickness of approximately 170.03 μm, an ultralow porosity of 0.95%, and a high amorphous phase fraction of 76.19%. The surface hardness reached 808 HV0.2, nearly an order of magnitude higher than that of the ZK60A substrate. Electrochemical and immersion tests demonstrated that the coating dramatically reduced the degradation rate to 0.024 mm/year, which is 116.6 times lower than that of the ZK60A substrate (2.798 mm/year). This significant improvement is attributed to a dual-passivation mechanism. On the one hand, a dense Fe2O3/SiO2 enriched layer formed on the coating surface effectively suppressed chloride ion attack and charge transfer. On the other hand, the Si4+ and B3+ ions released during coating degradation promoted the formation of a secondary protective film. More importantly, the Si-OH and Fe-OH functional groups on the FeAC surface chemically anchored Ca2+ and PO43− ions, thereby inducing the formation of a hydroxyapatite layer (Ca/P = 1.65) within 9 days, indicating strong potential for osteogenesis. Collectively, these findings demonstrated that the FeAC synergistically enhanced corrosion resistance and bioactivity, providing a highly promising surface modification strategy for Mg-based orthopedic implants.

Graphical Abstract