Influence of cupric, ferric, and chloride on the corrosion of titanium in sulfuric acid solutions up to 85°C

Titanium is chosen as the construction material of autoclaves for pressure acid leaching of metal ores. The corrosion behavior of titanium was studied in sulfuric acid solutions with different additions of Cl^-, Cu ²⁺, and Fe³⁺ to simulate hydrometallurgical lixiviants at 25, 55, and 85°C. Electrochemical methods like open-circuit potential measurement, potentiodynamic polarization, potentiostatic polarization, and electrochemical impedance spectroscopy (EIS) were used to study the influence of these ions on the corrosion response of titanium in sulfuric acid. The chemical composition of titanium oxide films was examined further using x-ray photoelectron spectroscopy (XPS). Potentiodynamic polarization experiments demonstrated that the presence of Cl^-, Cu²⁺, and Fe ³⁺ facilitated the anodic passivity of titanium in sulfuric acid. EIS experiments showed that modest addition of Fe³⁺ (1.0 g/L) increased the polarization resistance most significantly. Both electrochemical experiments and surface analysis showed that the presence of Cu²⁺ affected the titanium oxide films, and the mechanism behind this effect is discussed in view of the obtained results.