A. A. Baikov Institute of Metallurgy and Materials Science, Moscow, Russia:

V. A. Bryukvin, Head of Laboratory, e-mail: brukvin@imet.ac.ru

A. O. Bolshikh, Leading Researcher

JSC “Norilsk Nickel MMC”, Norilsk, Russia.
V. T. Dyachenko, Head of Department of Innovation Development

Chair of Chemistry and Technology of Rare and Scattered Elements, Moscow State University of Fine Chemical Technologies, Moscow, Russia.
T. B. Elemesov, Post-Graduate Student

Chair of Materials Science of Semiconductors and Non-conductors, National University of Science and Technology "MISiS", Moscow, Russia.
E. A. Skryleva, Leading Researcher

Linear voltamperometry method was used for physical-chemical analysis of electrochemical behavior of metallic nickel in sulfuric acid solutions with different potentials of its constant current polarization with definition of polarization extension of its active anode dissolution and passivation areas. For the purpose of definition of passivation mechanism, the chemical composition of nickel electrode plates surface was analyzed by X-ray photoelectron spectroscopy method. According to results of analysis of component composition of the film, anodically blocking the nickel electrode surface, it contains up to 54% of O, 40% of Ni and 4.5% (atm) of S. According to the data about bonding energy of fine spectrums of Ni₂p₃, O_1s and S_2p, the nickel electrode passivation can be considered as a consequence of its anode oxidation to trivalent state with formation of Ni_х(OH)_уSO_z hydrosulfate on its reaction surface, blocking the boundary of phase division of nickel electrode with electrolyte. Extension of nickel passivation area is limited both by nickel polarization potential (until nickel reaches trivalent state), and by water decomposition with formation of oxygen, which oxidates the formed hydrosulfate, which provides the electrode surface depassivation, accompanied by transfer of nickel in electrolyte solution. Defined regularities of polarization behavior of nickel can be used for substantiation of mechanism and mode-parametric provision of hydrometallurgical sulfuric acid processing of mineral sulfide and oxide nickel-containing raw materials, depending on the value of oxidation potential of S:L reaction system.

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