Electrochemical Properties of TiAl-Based Alloys

TiAl alloys represent a promising potential for use in many fields including automotive, aerospace and marine industries. Therefore, it can be considered important to investigate the ability of these alloys to withstand such harsh environments. To this intended, the following study attempted to determine the electrochemical properties of Ti-48Al-2Mo-2(Cr,Mn) (at %) alloys in 3.5 wt % NaCl solution. The results of potentiodynamic polarization experiment revealed that Mo addition can enhance the corrosion resistance of the alloys, especially the Ti-48Al-2Cr alloy. Ti48Al-2Cr-2Mo was found to have the lowest corrosion rate value of 0.1153 mm/year, whereas Ti48Al-2Mn was found to have the highest corrosion rate value of 0.3952 mm/yr. The polarization resistance (R-p) of the alloys changes from 1.33 to 5.54 k Omega cm(2) depending on alloyed compositions. The electrochemical impedance spectroscopy (EIS) results confirmed that the corrosion behavior can be tailored through Mo addition. Accordingly, the best corrosion resistance belongs to the Ti48Al-2Cr-2Mo alloy, which presents the highest impedance value of 4.98 x 10(3) Omega. The surface morphologies of corroded alloys exhibited the pitting corrosion characteristics after the polarization experiments in 3.5 wt % NaCl solution. The number density of corrosion pits was significantly higher on the surfaces of the Ti48Al-2Mn and Ti48Al-2Mn-2Mo alloys. The enhanced corrosion resistance of Ti48Al-2Cr-2Mo alloy to NaCl solution is believed to be associated with the coupled positive effect of Cr and Mo in forming a surface film with a good protective ability. In addition, Ti48Al-2Cr-2Mo exhibited high resistance to NaCl solution at a level, which can be considered an optimum material for fabricating parts that serve in the marine environment.