Enhancement of corrosion resistance and mechanical properties of Mg–1.2Ca–2Bi via a hybrid silicon-biopolymer coating system

• Si/PCL coating is fabricated on the Mg alloy by combined PVD and dip coating.
• Bonding strength of the Si and Si/PCL coating was investigated.
• Si/PCL coating significantly enhance the corrosion resistance of Mg alloy.
• Compressive strength of Si/PCL is higher than uncoated sample after immersion test.

In this work, a hybrid dual layer surface coating consisting of a silicon (Si) underlayer and poly(ε-caprolactone) (PCL) overlayer was investigated that was designed to reduce the corrosion rates of magnesium-based biomaterials. The Si underlayer was 1.2 μm thick and composed of spherical nanoparticles. The overlayer of PCL was 75.2 μm thick and comprised network of pores. Corrosion-induced reduction of the compressive strength of a Si/PCL-coated Mg–Ca–Bi alloy was lower than that of the uncoated or Si layer-coated alloys. However, the bonding strength of the Si coating (24.6 MPa) was significantly higher than that of the Si/PCL-coated samples (6.8 MPa). The Si/PCL coating dramatically enhances the charge transfer resistance of the Mg alloy (2.11 kΩ cm2) in simulated body fluid when compared with a Si-coated sample (2265.12 kΩ cm2). Si/PCL coatings are considered a promising route to control the corrosion rate and mechanical properties of Mg-based biomaterials.

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