Corrosion Resistance of Titanium-Ruthenium Alloys

The corrosion resistance of various Ti-Ru alloys (0.07 to 0.55 Wt% Ru) has been evaluated and compared with published data on Ti-Pd alloys. The results show that Ti-Ru alloys (1) are comparable with Ti-Pd alloys in terms of corrosion resistance in dilute (0 to 10%) boiling H₂SO₄ solutions, and are only slightly inferior in HCl solutions, (2) pick up less total hydrogen during corrosion than unalloyed Ti or a Ti-Pd alloy, and (3) exhibit no detectable corrosion when an oxidizer (i.e., FeCl₃) is added to the boiling acids. Corrodent analysis and the dependence of the cessation of corrosion on the volume of corrodent, suggest that the mechanism of passivation in H2SO4 solutions involves dissolution and re-precipitation of Ru back onto the alloy surface. A similar mechanism is thought to be operative in HCl solutions, although the data suggest that in the latter there is less tendency for the Ru to re-precipitate.