Corrosion resistance of Ti6Al4V alloy coated with caprolactone-based biodegradable polymeric coatings

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The aim of this study was to determine the influence of long-term exposure of Ringer’s solution on degradation of the anodically oxidated Ti6Al4V alloy coated with a biodegradable polymer coating. Polymeric coatings made of poly(glycolide-ε-caprolactone) – G-Cap and poly(glycolide- ε-caprolactone-lactide) – G-Cap-L were applied by a dip-coating method. Degradation was assessed on the basis of the results of pitting corrosion resistance and density of metal ions infiltrating to the solution. Studies were conducted for samples after 3, 6, 8, 10 and 12 weeks of exposure to the corrosive environment. In addition, topography of the surface of the polymer coating was assessed. As a result of potentiodynamic studies, the value of the polarization resistance and corrosion potential for the G-Cap and G-Cap-L coated samples were significantly decreased while simultaneous reduction of the density of metal ions infiltrating to the solution throughout the whole study period. There was also observed a faster degradation of the G-Cap coating compared to G-Cap-L, which showed local discontinuity after 12 weeks of exposure. The obtained results provide the basis for the development of polymeric coatings on surface of metal implants with predictable time / kinetics of degradation by selecting the composition of polymers while simultaneous limitation of metal ions infiltration into surrounding tissues.