Morphological effects on the electrochemical dissolution behavior of forged and additive manufactured Ti-6Al-4V alloys in runway deicing fluid

The particular microstructure of Ti-6Al-4V fabricated by additive manufacturing (AM) makes it exhibit a different corrosion resistance compared with that of the conventional forged Ti-6Al-4V. Here we utilize the electrochemical impedance (EIS) and potentiodynamic polarization (Tafel) to evaluate the electrochemical dissolution behavior in runway deicing fluids (RDF) of three kinds of Ti-6Al-4V alloy, which are respectively fabricated by forging, electron beam melting (EBM), and selective laser melting (SLM). The microstructure and electrochemical results suggest that EBM samples have a better corrosion resistance than others', which is attributed to an appropriate proportion of α-lath width and the volume fraction of β phase. A higher relative proportion of TiO2 is formed on surface, resulting in the fine-lamellar structure with a higher density of grain boundaries. Besides, the corrosion resistance anisotropy of AMed Ti-6Al-4V samples is ascribed to the existence of β columnar gains. In addition, the acicular martensite α′ phase with metastable structure leads to the worst corrosion resistance of SLMed Ti-6Al-4V samples. This work enriches the corrosion resistance of Ti-6Al-4V alloy in strong electrolyte solutions, which helps to promote the service performance of aviation titanium alloys in harsh environments. [Display omitted] •EBM Ti-6Al-4V is more stable than forged one in runway deicing fluids (RDF).•There is anisotropy of corrosion in EBM and SLM Ti-6Al-4V alloys.•The passivation film formed on the SLM Ti-6Al-4V alloy is fragile due to α′ martensite.•The fine-lamellar α affects the proportion of Ti oxides formation on the surface.•Corrosion preferentially occurs at the grain/interfacial boundaries on the surface of Ti-6Al-4V.