The corrosion characteristics of Ti-6Al-4V manufactured via directed energy deposition was investigated through microdroplet cell and electrochemical tests, as well as electrochemical impedance spectroscopy and critical pitting temperature (CPT) measurements. The results confirmed that the acicular martensitic alpha' phase plays an important role in determining the corrosion behavior of additive-manufactured Ti-6Al-4V, differing from that of conventional Ti-6Al-4V. X-ray diffraction analysis and micro-Vickers hardness measurements were facilitated to identify the alpha' phase. Meanwhile, microdroplet cell tests were performed to assess the corrosion resistance of bright and dark grains on the additive manufacturing ( AM) Ti-6Al-4V. The CPT were also measured to evaluate the resistance of AM Ti-6Al-4V with various amounts of alpha' phase and that of a conventional Ti-6Al-4V alloy to pitting corrosion. Based on the result, the decrease in the resistance of AM Ti-6Al-4V to both uniform and pitting corrosion is attributed to the acicular martensite alpha' phase. (C) 2019 The Electrochemical Society.