Abstract Ti-9Mn alloy, widely used in aerospace and hydrogen storage, was recently introduced for use in marine and offshore structures because of its competitive mechanical characteristics. In this study, passive behavior of Ti-9Mn alloy was compared to the commercially pure titanium (cp-Ti). Ti-9Mn exhibited lower charge-transfer resistance than cp-Ti. Under steady-state condition, resistivity at metal /oxide film interface for Ti-9Mn alloy, which increased as fa unction of applied passive potential in range of 0.5 to 1.5 VSCE, was found to be lower than that of cp-Ti. Complex-capacitance (C∞) value for Ti-9Mn alloy was higher than that of cp-Ti. Presence of Mn in the alloy induced significant increase in current density when potential exceeds 1.5 VSCE. Corrosion current density of Ti-9Mn (16.2 ± 4.0 nA cm-2) was three times higher than that of cp-Ti (4.57 ± 0.7 nA cm-2) after 21 days immersion in 3.5 wt% NaCl. The study may allow us to realize the full potential passivation behavior of Ti-9Mn for future marine and offshore applications.