Electrochemical behaviour of Ti-6Al-4V alloy with different microstructures in a simulated bio-environment
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The electrochemical behaviour of the Ti-6Al-4V ELI alloy with different microstructures was investigated in Ringers solution at 25 degrees C. It was found that the properties of both inner barrier and outer porous layers of the passive film were dependent on the microstructural morphology and distribution of the alloying elements resulting in various amounts of their oxides incorporated in the TiO2 matrix. A more resistant and capacitive barrier layer formed on the alloy with fully lamellar, martensitic and globular microstructures in different thickness assured its high corrosion protection. The improved corrosion resistance of the alloy with equiaxed microstructure was provided by the existence of the larger amounts of the Al2O3 and V2O5 oxides, contributing to higher resistance of the outer porous layer. The Al2O3 amount is smaller than that of the V2O5 oxide due to its higher dissolution, especially in the case of the alloy with fully lamellar microstructure, resulting in the forma...tion of a more porous outer layer.