High temperature corrosion of titanium under conditions relevant to pressure leaching: Mass loss and electrochemistry

The corrosion behavior of titanium was studied using mass loss and electrochemical measurements in sulfuric acid with Cl^-, Cu²⁺, and Fe³⁺ additions up to 175°C. The corrosion rate of titanium in 30 g L^-1 H₂SO₄ + 12 g L^-1 Cl^- solution at 150°C measured by mass loss was higher than 62 mm y^-1. The corrosion rates of titanium under simulated pressure-leaching conditions determined by both mass loss and polarization resistance measurements were consistent, and also suggest that Cu²⁺ and Fe³⁺ ions are excellent corrosion inhibitors for titanium. Results from mass loss and electrochemical measurements all confirmed that the corrosion rate of titanium decreased remarkably with the addition of 1 g L^-1 Fe³⁺ to the leaching solution at 150°C, and that the presence of Fe³⁺ is the most important factor for the growth of titanium oxide films under pressure-leaching conditions. In addition, iso-corrosion diagrams, with 0.1, 0.5, and 1 mm y^-1 lines for titanium in H₂SO₄ solutions from room temperature to 175°C, were constructed from mass loss data.