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

In this work, a hybrid dual layer surface coating consisting of a silicon (Si) underlayer and poly(s-caprolactone) (PCL) overlayer was investigated that was designed to reduce the corrosion rates of magnesium-based biomaterials. The Si underlayer was 1.2 mu m thick and composed of spherical nanoparticles. The overlayer of PCL was 75.2 mu m 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 k Omega cm(2)) in simulated body fluid when compared with a Si-coated sample (2265.12 k Omega cm(2)). Si/PCL coatings are considered a promising route to control the corrosion rate and mechanical properties of Mg-based biomaterials. (C) 2015 Elsevier B.V. All rights reserved.