Corrosion behavior of Ti-6Al-4V alloy has been investigated in acid rainwater (ARW) at different pH values using various electrochemical techniques and scanning electron microscope examination. This work is important environmentally and industrially. The results obtained from polarization measurements showed that corrosion current density, i(corr), decreases with increasing pH of the ARW from 1.0 to 3.5. Electrochemical impedance measurements are in good agreement with polarization measurements. Also, the effects of adding different anions (Cl-, F- or SO42-) to ARW of pH = 1 were tested. It was found that increasing fluoride ion concentration leads to an increase in the corrosion rate of Ti alloy. For the chloride anion, the corrosion rate increases up to 0.05 M then decreases again at 0.1 M concentration. However, adding SO42- anion leads to a decrease in corrosion rate with increasing concentration. Scanning electron microscope images confirm well electrochemical impedance spectroscopy and polarization results.