Electrochemical Corrosion Behavior of Ti70 Alloy in HF-HNO₃ System

The electrochemical corrosion behavior of Ti70 alloy in HF-HNO3 system was investigated by measurements of open-circuit potentials, EIS and polarization curves. The results show that the corrosion rate of Ti70 increased with the HF concentration increasing. When the HF concentration was constant, the open-circuit potential decreased and the capacitance arc increased with increasing the volume ratio of HNO3 to HF. The obvious active-passive transition could be seen in the polarization curves. At the early stage of corrosion, an inductive arc at low frequency appeared. With extending the immersion time, a compact passivated film formed on the alloy surface. Two capacitance arcs appeared at high and medium frequencies respectively.