Corrosion and pitting behaviour of ultrafine eutectic Ti-Fe-Sn alloys

Ultrafine structured Ti70.5Fe29.5 and Ti67.79Fe28.36Sn3.85 eutectic rods comprising of β-Ti and TiFe phases were prepared by copper mould casting. The corrosion and passivation behaviour were investigated in halide free aqueous media (pH 1-13) by means of potentiodynamic polarisation and potentiostatic current transient measurements. Both eutectic alloys exhibit excellent corrosion resistance due to spontaneous passivation. The passive film compositions grown several nanometres on single phase polycrystalline specimens were analyzed with Auger electron spectroscopy. They consist of oxidized Ti and Fe species. Layers grown in strongly acidic environment are depleted in Fe. Sn was detected only on layers grown on the constituent β-Ti phase and only in the metallic state. The pitting susceptibility was investigated in strongly acidic media (pH ≤ 1) containing 0.1-3 M of chloride ions. The Sn-containing eutectic alloy was found to be more susceptible to pitting corrosion.