Uniform Corrosion of Titanium under Medium Temperature Chalcopyrite Concentrate Leaching Conditions

"The corrosion of commercially pure titanium (CP-Ti) was studied from room temperature up to medium temperature (~160°C) under conditions relevant to medium temperature chalcopyrite leaching processes. The corrosion rates were measured by immersion and electrochemical tests in sulfuric acid. The influences of chloride, cupric and ferric ions on the corrosion rate and behavior were also investigated. Corrosion of the CP-Ti did not account for the total current density measured by linear polarization tests. The corrosion rates of CP-Ti under medium temperature leaching conditions were surprisingly high. The corrosion rate measured in ferric containing solution at 160°C was approximately 20 mm/yr.INTRODUCTIONTitanium exhibits excellent corrosion resistance in many aggressive environments because of the formation of a very chemically stable, highly adherent, and protective oxide film on its surface (Mitsuo et al., 2002). Because titanium is the only metal available at a reasonable cost that resists the high temperature corrosive slurries in many leaching processes, it is often chosen as autoclave liner material where it is subjected to severe conditions of acidity, temperature and pressure (Grauman and Say, 2000).A number of distinctly different hydrometallurgical processes for the pressure leaching of chalcopyrite have been developed and patented by various companies and they can be classified into low, medium and high temperature regimes (McDonald and Muir, 2007). For example, chalcopyrite concentrate may be processed at medium temperatures (115-175°C) and pressures of 800-2200 kPa (Dreisinger, D., 2006; Sahu and Asselin, 2011). The lixiviant may contain 20 to 55 g/L sulfuric acid, 8 to 12 g/L chloride ions, 10-25 g/L Cu2+ (Jones, 1995, 1997, 1999), and less than 1 g/L Fe3+ (Defreyne et al., 2005). The amount of these additions is determined by the grade of the ores and details are shown in Table 1."