Developing a non-magnetic Fe-Mn coating for enhanced performance of biomedical magnesium alloys

To mitigate the rapid degradation rate of biodegradable magnesium alloys and ensure their long-term structural integrity, constructing functional metallic thin films on the alloy surface has emerged as a key research strategy. In this study, a non-magnetic FeMn coating was fabricated on WE43 magnesium alloy using FCVA deposition. The alloying of Mn effectively eliminated the magnetic response of the Fe layer. The relationships between deposition parameters and the corrosion resistance as well as mechanical performance of the alloy surface were systematically investigated, and the optimal FeMn coating parameters were identified. The microstructure, corrosion protection mechanisms of the coatings were thoroughly examined to achieve both controlled degradation and enhanced biofunctionality. Morphological analysis revealed that the number of large surface particles first decreased and then increased with increasing negative bias voltage. XRD results confirmed the presence of a multiphase structure comprising Fe, Mn, γ-FeMn, and ε-FeMn. At a bias voltage of −75 V, the FeMn coating exhibited the fewest surface defects and the lowest corrosion current density (I_corr) of 43.93 μA cm−2. Compared to the pure Fe coating, the I_corr of the FeMn layer was reduced by approximately 45 %, indicating improved short-term corrosion resistance. Moreover, at −75 V, the coating achieved the highest hardness (12.36 ± 0.84 GPa) and elastic modulus (118.89 ± 5.30 GPa). These findings offer new insights for the clinical application of biodegradable magnesium alloys and provide a valuable reference for the development of advanced degradable coating systems.