Corrosion resistance evaluation of biodegradable magnesium alloy vascular stents optimized by mechanical adapted polymer coating strategy

Abstract

Surface modification coating of magnesium alloy stents as a physical barrier is to inhibit the corrosive medium from contact with matrix. In view of the complex deformation behavior of stent, mechanical adopted polymer coating strategy was considered in our work. Here, a relatively high plasticity polymer- poly(butyl acrylate) (PBA) was applied as the outer protective layer on the surface of magnesium alloy discs and stents through a dip-coating method and ultrasonic spraying system respectively. Compared with low plasticity poly(d,l-lactide) (PDLLA) control group, mechanical property of PBA polymer film were detected, furthermore, the static corrosion behaviors of PBA/MgF2 flake samples were investigated by electrochemical and immersion tests for a period time. The morphologies and degradation behaviors of stents after grip-expansion were conducted to explore the mechanical adaptability of PBA/MgF2 coating with magnesium alloy stent. PBA/MgF2 composite coating could improve the corrosion resistance of both static and deformed magnesium alloys, exhibiting a long-term protection. Especially, PBA-coated stent maintained the structural integrity and a relatively smooth surface after 21 days of service. Therefore, it is inferred that a coating material with high elongation at break is more mechanical adaptability with stent deformation to reduce the degradation rate of magnesium alloy stents.