Differences in electrochemical corrosion behaviours between selective laser melted and wrought Ti6Al4V alloys in acid fluoride-containing artificial saliva

In this work, the electrochemical corrosion behaviours of selective laser melted (SLMed) and wrought Ti6Al4V alloys in acid fluoride-containing artificial saliva were examined. The SLMed Ti6Al4V alloy exhibits a metastable microstructure with mainly acicular α′ phase with rare prior β phase, while the wrought Ti6Al4V alloy displays an equiaxed α phase with granular β-phase. The alloying elements of SLMed Ti6Al4V alloy are more homogeneous distributed compared to wrought Ti6Al4V alloy. The alloys manufactured by the two ways demonstrate differences in active dissolution, active–passive transition, and passivation behavior based on electrochemical approaches and surface characterization. All electrochemical characteristics indicate that the corrosion resistance of SLMed Ti6Al4V alloy is inferior to that of wrought Ti6Al4V alloy. The differences in corrosion mechanism between SLMed and wrought Ti6Al4V alloys can be attributed to the following stages. In the active dissolution state, the SLMed alloy provides much more sites to react with aggressive ions. In the active–passive transition state, SLMed Ti6Al4V alloy needs to form more amount of passive film to inhibit active dissolution. In the passive state, the passive film on SLMed Ti6Al4V alloy is less protective.