Polarization curves and Auger spectroscopy are used to study the kinetics, formation mechanism, and layer-by-layer phase composition of oxide films resulting from the anodic oxidation of SiCTiB 2 -B 4 C ceramics containing 10 wt.% and 40 wt.% TiB 2 in 3% NaCl solution. It is shown that a two-layer oxide film forms in the former case (β-Ti 2 O 3 is the lower layer and TiO 2 the upper one) and a three-layer film forms in the latter case (nonstoichiometric β-TiO is the upper and lower layers and β-Ti 2 O 3 the intermediate one). All ceramic samples, especially those with 10 wt.% TiB 2 , have high corrosion resistance.Composites in the SiC-MeB 2 system have excellent mechanical properties, such as bending strength, hardness, and wear resistance, and can widely be used in industries that require high-strength and corrosionresistant materials [1-3]. Ceramic SiC-TiB 2 -B 4 C composites are promising for commercial applications. Their corrosion behavior in electrolytes that imitate natural media is of considerable interest. Although the applications of these materials hold much promise, there are not many studies on their electrochemical corrosion properties, and the published data [4] on corrosion focus only on a mixture of nitrates and fluorides. This paper examines the kinetics and mechanisms of anodic oxidation of composites in the following ternary ceramic systems: 85 wt.% SiC-10 wt.% TiB 2 -5 wt.% B 4 C (89.7 mol.% SiC-6.4 mol.% TiB 2 -3.9 mol.% B 4 C) and 55 wt.% SiC-40 wt.% TiB 2 -5 wt.% B 4 C (66.2 mol.% SiC-29.4 mol.% TiB 2 -4.4 mol.% B 4 C) in a 3% NaCl solution imitating natural corrosive media.The tests samples were produced by hot pressing [3] at 2150°C from a powder mixture of UF-10 silicon carbide α-SiC (Starck Company, Germany), titanium boride TiB 2 as per TU 6-09-03-7-75 (Donetsk Chemical Reagents Plant), and abrasive boron carbide B 4 C as per GOST 5744-74 (Zaporozh'e Abrasive Plant). After 10-min hot pressing, the phase composition of the samples was examined with x-ray diffraction (XRD) using a DRON-3M diffractometer (Cu-K α radiation); porosity of the samples was ≤8%.Electrochemical corrosion of the samples was examined using potentiodynamic curves and a PI-50-1 potentiostat with a potential sweep rate of 0.5 mV/sec. The current density as a function of potential was measured relative to an Ag/AgCl/KCl reference electrode. All the potentials are relative to this standard reference electrode.

UDC 621:921:661.65The paper examines the mass transfer kinetics, structure, and properties of spark-deposited coatings on magnesium alloys. They are obtained using composite ceramic electrodes in the AlN-Zr(Ti)B 2 and B 6 Si-CaB 6 systems. It is revealed that the microhardness and corrosion resistance of the coatings increase in a 3% NaCl solution and the abrasive wear decreases as compared with uncoated magnesium alloy.

The paper examines the corrosion behavior of amorphous TiB 2 films 70-250 nm in thickness and amorphous-crystalline films with crystals 15-90 nm in size in 3% NaCI solution. It is shown that the corrosion resistance and passivation anodic potential increase with thickness of TiB 2 amorphous films. It is also established that TiB 2 films are oxidized through pitting corrosion. The corrosion instability of amorphous films is mainly due to their interaction with impurity (in particular, oxygen and carbon) structural inhomogeneities and of amorphous-crystalline films due to the interaction with amorphous-crystalline boundaries. The corrosion resistance of amorphous TiB 2 films is approximately 4000 times higher than that of bulk powder material and 8 to 10 times higher than that of amorphous-crystalline films.Diborides of transition metals are radically new materials in thin-film technology. The unique combination of high conductivity, high heat resistance, exceptional chemical inertness, and low electron work function makes them unique candidates for use in heat-resistant high-conductivity layers, Schottky contacts with n-Si and n-GaAs, and diffusion barriers in multilayer contacts with semiconductors [1, 2]. The corrosion properties of ceramic films of titanium nitride and boride have recently been of increasing interest. This is because these compounds are promising thin-film protective coatings [3,4].However, there are no publications on the research of the corrosion resistance of thin nanostructured TiB 2 films in liquid corrosive media.The objective of this paper is to study the corrosion behavior of nanostructured TiB 2 films in 3% NaCl solution. To ascertain the mechanism of the process, the microstructure of the films after corrosion tests was examined.The corrosion tests were conducted using the electrochemical method of plotting potentiodynamic polarization curves (PI-50-1 potentiostate, scan rate 0.5 mV/sec). The anodic potentials were measured in 3% NaCl solution, which is conventionally used in corrosion tests (sea-water imitation). The potentials in this paper are relative to the standard reference silver-silver chloride electrode.