Effect of Nb Addition on the Corrosion Behavior of Porous TiAl Based Alloys in Aqueous Environments

Abstract

The corrosion behavior of porous Nb-containing TiAl based alloys in HCl, NaOH and NH3H2O aqueous solutions with various concentrations has been studied simultaneously at room temperature. The results indicate that the porous alloys have good acidic resistance which is probably based on the combined work of Ti-Ti metallic bond and covalent bond. And pitting corrosion is the main corrosion behavior of Nb-free TiAl alloys during the first 40 hours, while intergranular corrosion is the main corrosion behavior later. Nb-containing alloys have better acid corrosion resistance due to inhibiting intergranular corrosion by Nb element. In addition, the porous TiAl based alloys are much more resistant to corrosion in alkaline solutions than in acidic solutions, owing to the different oxide films formed in alkalis solutions.