Gipronickel Institute LLC, St. Petersburg, Russia

Yu. N. Lisakov, Senior Researcher, Hydrometallurgy Laboratory, Candidate of Technical Sciences, e-mail: LisakovYuN@nornik.ru
O. V. Pavlov, Leading Engineer, Hydrometallurgy Laboratory, e-mail: PavlovOLV@nornik.ru
N. P. Chuprynin, Category II Engineer, Hydrometallurgy Laboratory, ChupryninNP@nornik.ru

Kola Mining and Metallurgical Company JSC, Monchegorsk, Russia
G. E. Naumenko, Chief Engineer, Chemical and Metallurgical Shop, e-mail: NaumenkoGE@kolagmk.ru

Corrosion tests of several nickel-based structural alloys and samples of technical titanium grade VT1-0 were conducted under conditions of intense corrosion wear: high salt background, up to 15 g/l of chlorine ion, 50 g/l of H2SO4, significant process temperature of 200 ^oC, partial oxygen pressure of 0.5 MPa. It was found that only titanium alloy grade VT1-0 has sufficient corrosion resistance. The choice of material for the manufacture of housing equipment and mixing devices operating at a temperature of 200 ^oC and oxygen supply is complicated by the problems of using titanium in an oxygen atmosphere. To date, the work of domestic and foreign scientists on the study of titanium flammability under autoclave processes has established that titanium ignition in a dry oxygen atmosphere at a temperature of 425 K occurs already at a partial oxygen pressure of 0.1–0.3 MPa in the presence of an external exciter (spark), especially when the integrity of the oxide film is compromised. Therefore, corrosion studies were carried out on samples of NT-47 grade titanium-niobium alloy, resistant to combustion in an oxygen atmosphere. Experiments were carried out with samples that had not undergone hardening treatment, and with heat treatment of the metal. The results of the study showed that hardening surface treatment led to a decrease in the corrosion rate of the NT-47 alloy by two to three times. The most effective method of surface hardening among those tested is thermal oxidation. Microarc oxidation and laser processing are also highly effective, but these methods seem more difficult for industrial implementation.

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