622 ISSN 2070-2051, Protection of Metals and Physical Chemistry of Surfaces, 2016, Vol. 52, No. 4, pp. 622–626. © Pleiades Publishing, Ltd., 2016. Original Russian Text © S.M. Gorelov, T.E. Tsupak, E.G. Vinokurov, Kh.A. Nevmyatullina, O.V. Yarovaya, 2016, published in Fizikokhimiya Poverkhnosti i Zashchita Materia- lov, 2016, Vol. 52, No. 4, pp. 386–390. Preparation and Properties of Nickel–Zirconia Nanocomposite Coatings S. M. Gorelov, T. E. Tsupak, E. G. Vinokurov, Kh. A. Nevmyatullina, and O. V. Yarovaya Mendeleev University of Chemical Technology of Russia, Moscow, Russia Ministry of Education and Science of the Russian Federation e-mail: vin-62@mail.ru Received November 19, 2015 Abstract—The possibility of preparing and properties (surface morphology, microhardness, corrosion resis- tance) of nickel–zirconia composite coatings electrodeposited from nickel acetate solutions containing a dis- persed phase in the form of a conventional polydisperse crystalline micropowder and a sol with nanoscale particles have been discussed. The effect of the particle size and concentration and the electrolysis conditions on the properties of the coatings has been determined. DOI: 10.1134/S2070205116040134 INTRODUCTION An improvement of the properties of electrodepos- ited coatings and an expansion of the range of applica- tion thereof can be implemented via modifying the coatings with dispersed phase (DP) particles [1]. Elec- trochemical composite coatings (CCs) can exhibit high corrosion stability, wear resistance, and micro- hardness [1, 2]. Oxides, sulfides, nitrides, carbides, and borides of metals and carbon materials (ultrafine diamond, graphite, fullerenes, and carbon nanotubes) are used as a DP in the preparation of CCs [3–6]. Titanium subgroup metal oxides—titania and zir- conia—are of considerable interest as a DP, as evi- denced by the large number of publications on this subject in recent years [7–10]. The introduction of titania or zirconia particles larger than 100 nm into a nickel-plating solution leads to an increase in the microhardness, wear resistance, and protective ability of the coatings [11–13]. Practicable results are obtained at high DP concentrations (10–100 g/L) in nickel-plating solutions, which typically cause sedi- mentation of DP particles in slurry solutions [14]. A nonuniform distribution of DP particles in the solu- tion and near the surface of the coated parts during electrodeposition has a significant effect on the prop- erties of CCs. To solve this problem, a variety of meth- ods are used to maintain the stability of the nickel- plating solution–DP particle slurry: hydrodynamic methods (bubbling, solution circulation, and ejec- tion), stabilization of particles in solution by means of surfactants of different natures [15, 16], and the use of stable sols containing nanoparticles. Thus, the forma- tion of high-quality CCs depends not only on the elec- trodeposition conditions and the composition of the DP and the solution, but also on the sedimentation stability of the slurry. The aim of this study is to examine the morphol- ogy, microhardness, corrosion resistance, and com- position of nickel–zirconia coatings electrodeposited from slurries and sols based on a nickel-plating solu- tion containing zirconia particles of different sizes and concentrations. EXPERIMENTAL Nickel–zirconia coatings were deposited using a solution (a pH of 4.3–4.7) with the following compo- sition, mol/L: Ni(СН 3 СОО) 2 · 4 H 2 O, 0.24–0.32; NiCl 2 · 6 H 2 O, 0.03–0.063. After dissolution of the main components, the solution was exposed to hydro- gen peroxide (1–2 mL/L) under heating and subjected to pre-electrolysis at a low current density to clear the solution from organic and inorganic impurities [17]. The solution pH was adjusted with acetic acid. A TiO 2 sol, crystalline ZrO 2 , and a zirconia sol were used as the second phase of the solution. The sol preparation technique is described in detail in [18]. The DP particle size distribution in the solutions was studied using a Nanotrac instrument. Coatings were electrodeposited on an M1 copper foil and steel (08kp) plates at a solution temperature of 45–55° C and a cathodic current density of 200– 1200 A/m 2 . H0 nickel was used as the anodes. Pre- liminary surface preparation of the samples was con- ducted according to standard procedures [17] includ- ing degreasing, activation, and rinsing. The coatings were deposited in a 300-mL thermostated glass cell. NANOSCALE AND NANOSTRUCTURED MATERIALS AND COATINGS