Saint Petersburg Mining University, Saint Petersburg, Russia:

V. I. Bolobov, Professor of a Chair of Mechanical Engineering, e-mail: Boloboff@mail.ru

LLC “Scientific-Research Center “Gidrometallurgiya”, Saint-Petersburg, Russia:
I. V. Fomenko, Research Director

Kazakhmys Corporation LLP, Almaty, Kazakhstan:
A. A. Shakhalov, Project Manager of Department of Complex Processing of Technogenic Raw Materials
E. A. Ospanov, Head of Department of Complex Processing of Technogenic Raw Materials

This article presents the results of corrosion tests of potentially possible structural materials of autoclave equipment. Tests were carried under conditions that simulates the conditions of two different stages of autoclave treatment of sulfide copper concentrates:
– pressure oxidation (POX) — under temperature 170 ^oC and oxygen overpressure 0.3 MPa;
– hydrothermal alteration (HTA) — reduction process carried out at the same temperature, without oxygen and under different concentrations of copper ions in solution.
POX batch experiments showed that Hastelloy G35, AISI 316, AISI 904L, SAF 2205, SAF 2507 has a sufficiently high corrosion resistance (P ≤ 1 mm/year) and can be used as a construction materials for POX leaching of sulfide copper concentrates (170 ^оC, P_O2 = 0.3 MPa, P_Σ = 1.0 MPa, C_H2SO4 = 45 g/L, C_Cu²⁺ = 42 g/L), even in presence of relatively high concentrations of chloride ions (up to 170 mg/L). HTA batch experiments showed that Hastelloy G35, C22-HS, C-2000, AISI 904L and titanium has a sufficiently high corrosion resistance (P ≤ 1 mm/year) and can be recommended as construction materials for autoclave equipment of HTA stage (170 ^оC, PN₂ = 0.3 MPa, P = 1.0 MPa, CH₂SO₄ = 45 g/L, ORP less than 300 mV), even in presence of relatively high concentrations of chloride ions (up to 240 mg/L), but only when copper concentration in solution is greater than 0.038 g/L. When copper concentration is less than 0.006 g/L, all tested chromium-nickel alloys and steels showed low corrosion resistance (P  100 mm/year). The corrosion rate of titanium in these conditions increases to 0.30 mm/year. Authors attribute this phenomenon to the appearance of hydrogen sulfide under HTA conditions.

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