Saint Petersburg Mining University, Saint Petersburg, Russia:
V. I. Bolobov, Professor of a Chair of Mechanical Engineering, e-mail: Boloboff@mail.ru

Scientific and Research Center “Gidrometallurgiya”, Saint Petersburg, Russia:
Ya. M. Shneerson, Chief Executive Officer, Professor
A. Yu. Lapin, Technical Director

Our paper shows the results of comparative corrosion tests of some of the materials to be used in equipment for high-temperature oxidation leaching of gold-bearing sulfide concentrates: hyperduplex steel SAF 2707 (Sandvik Materials Technology); duplex steel SAF 2507; austenite steel AISI 904L, inconel 625 and experimental-industrial steel Hastalloy G35 (Haynes International Inc.). The samples were tested in a laboratory autoclave; they were put under effect of respective gas and liquid phases of products, obtained by high-temperature leaching of refractory gold-bearing sulphide ore with an increased level of sulphur and chlorine-bearing compounds (~54 g/l H₂SO₄ and 40 mg/l Cl^–), at a temperature of 225 ^oC, a 3.2 MPa total pressure in the autoclave throughout 100 hours. The determined values of weight and depth indexes of corrosion rate (K g/(m2·h) and P mm/year) were compared to K and P indexes, obtained at testing of the same materials at the same operating parameters in the pulp of hightemperature pressure leaching semi-industrial unit with a lower level of H₂SO₄ and Cl^–. The corrosion rate indicators for all tested materials in liquid phase of the autoclave were more than 10 times higher than the corresponding values for gaseous phase and higher than those in the semi-industrial unit’s pulp. This may be explained by a high amount of sulphuric acid and chlorine-ion in the solution. Among those that were tested, hastalloy G35 is the only resistant material in high-temperature leaching products. Other tested materials (including the hyperduplex steel 2707) may belong to the low-resistant ones. The alloy G35 is not exposed to crevice corrosion and ignition risk. That is the only reason why this alloy (along with titanium) is more suitable for manufacturing of elements of autoclave equipment for high-temperature leaching processes.

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