Electrochemical behavior of titanium-tantalum alloys in sulfuric acid solutions

摘要

Titanium exhibits a good corrosion resistance in oxidizing acids and neutral media but it is severely attacked in reducing acids. On the contrary, tantalum presents an excellent resistance in both oxidizing and reducing acids, but its high cost limits its use to very aggressive conditions. The titanium-tantalum alloys are promising materials for use in reducing acids, due to their lower cost and density when compared to tantalum, and their higher corrosion resistance when compared to titanium, Titanium-20, 40, 60 and 80 wt% tantalum alloys were prepared by arc-melting and their microstructures were characterized by scanning electron microscopy and X-ray diffractometry. Their electrochemical behaviors were studied in 20 to 80 wt% sulfuric acid solutions at room temperature, using open-circuit potential measurements, potentiodynamic polarization and electrochemical impedance spectroscopy. Different behaviors were observed depending on the tantalum content and acid concentration. A clear tendency of increase in corrosion resistance with the increase of tantalum content is observed, especially in 80 wt% sulfuric acid solutions.