Corrosion of titanium-aluminum intermetallides.: II.: Electrolytic oxidation of γ-TiAl, TiAl3, and α2-Ti3Al in sea water

Potentiodynamic polarization, XRD, Auger electron spectroscopy, and scanning electron microscopy have been applied to determine the mechanisms of electrolytic corrosion of the intermetallides,gamma-TiAl, TiAl3, and alpha(2)-Ti3Al in 3% NaCl solution with the addition of MgSO4 in comparison with the corrosion of the pure metals (Al and Ti). There is comparatively high corrosion resistance in TiAl and Ti3Al because of the protective action from thin films of rutile TiO2. Evidence is obtained or the differences between these intermetallides from the appearance of pure titanium on deep anodic polarization (above +0.15 V for TiAl and +0.7 Vfor Ti3Al): the aluminum and titanium enter the solution in the forms of Al3+ and TiO2+ and intermetallides dissolve rapidly. The final solid-state products from anodic oxidation in that case are rutile, magnesium aluminate, and also magnesium and sodium titanates. In addition to pure titanium,gamma-TiAl and alpha(2)-Ti3Al as constructional materials may be recommendedfor use in sea water.