Corrosion and passivation of annealed Ti–20Zr–6.5Al–4V alloy

• Corrosion of novel Ti–20Zr–6.5Al–4V alloy is investigated.
• Spontaneous passivity behavior is observed in 3.5% NaCl solution.
• All the alloys exhibit an active–passive transition in 5% HCl solution.
• The α/β interphase boundaries act as the preferential dissolution locations.

Corrosion and passivation behaviors of annealed Ti–20Zr–6.5Al–4V alloys were investigated in NaCl and HCl solutions. All the alloys exhibited spontaneous passivity and low corrosion current densities in 3.5% NaCl solution. An active–passive transition behavior was observed in 5% HCl solution. The corrosion resistance decreased with the increase in annealing temperature. Scanning electron microscopy analysis of the samples after the immersion tests revealed that the α/β interphase boundaries act as the preferential dissolution locations. The volume fraction of β phase as well as the grain size was identified as the main factor affecting the corrosion performance of the alloys.

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