Corrosion behavior of hafnium in anhydrous isopropanol and acetonitrile solutions containing bromide ions

The corrosion behaviors of hafnium in Et₄NBr isopropanol and acetonitrile(ACN) solutions were investigated using electrochemical measurements, ICP-AES and SEM techniques. Results revealed that the open circuit potential gets more positive due to the increased passivity of the surface oxide film with increasing immersion time until it reaches a steady state value. The potentiodynamic anodic polarization curves did not exhibit an active dissolution region near corrosion potential due to the presence of an oxide film on the electrode surface, which was followed by pitting corrosion. SEM images confirmed the existence of pits on the electrode surface. Cyclic voltammetry and galvanostatic measurements allowed the pitting potential (?_pit) and the repassivation potential (?_p) to be determined. ?_pit increased with increasing potential scanning rate but decreased with increasing temperature, Br^? concentration and ACN concentration. The impedance spectra showed that the resistances of the solution and charge transfer decreased with the increase of ACN concentration.