Investigation of passive films on alpha(2) and gamma titanium aluminides by X-ray photoelectron spectroscopy

Passive films on alpha(2) and gamma titanium aluminide formed potentiostati cally in sodium hydroxide (NaOH) and sulfuric acid (H2SO4) solutions were s tudied by x-ray photoelectron spectroscopy (XPS), In NaOH, potentiostatic e xperiments showed that titanium aluminides had very similar passive current densities to that of Ti. XPS sputter depth profile showed nearly no Al pre sent in the outer layer of the passive films. In H2SO4, passive current den sities increased for specimens with increasing Al content. XPS sputter dept h profile showed that Al was enriched in. outer layers of the passive films . These results indicated that the passive film dissolution rate increased with increasing amounts of Al in the passive film for titanium aluminides.