Effect of alloying elements on corrosion properties of high corrosion resistant titanium alloys in high concentrated sulfuric acid
Bosung Seo, Hyung-Ki Park, Chang-Soo Park, Kwangsuk Park
Abstract
Alloying elements such as Ru, Nb and Ta were added to ASTM Grade 13 (Gr13) titanium alloy to obtain improved corrosion resistance, especially for the high reducing environment. TEM results showed that Ru was mainly used in forming the β-Ti precipitate, while Nb and Ta were detected in both β-Ti and Ti2Ni precipitates. TEM and APT analysis revealed that Ta was used as not only a substitution element for the precipitate but also the solid solution element, which was finally detected in the TiO2 film. From the OCP results considering the duration time to passivity loss, it can be inferred that the Ta provided the greatest impact on the stability of the TiO2 film against the high reducing condition. While, other alloying elements such as Nb and Ru gave predominantly an influence on the cathodic modification. EIS results also confirmed the excellent effect of Ta on improving the stability of the TiO2 film. Maintaining high corrosion resistance as well as one semicircle loop after the 24 hrs immersion for the Ta added titanium alloys reflected the good stability of the TiO2 film, while other titanium alloys showed two time constants with the decreased corrosion resistance.