Corrosion behavior plays a decisive role for biocompatibility of titanium alloy implants. In this study, Ti-5Al-2.5Fe alloy samples were formed through metal powder injection molding (MIM) process and their potentiodynamic tests were carried out in a phosphate buffered solution with and without HCl. Experimental results showed that the slope of current potential curves increased within the passive region. In comparison to results of samples processed by vacuum arc melting followed by annealing, existence of micro pores was considered to be a main factor for observed corrosion behavior of MIM processed sample. The observations were further discussed in detail based upon a model of electrochemical reaction system and quantitative equations for quasi-passive state.