V. I. Pokhmurs’kyi

Influence of hydrogen on the friction and wear of metals (a survey)

We analyze the literature sources devoted to the investigation of the influence of hydrogen on the tribological behavior of metallic materials. The specific features of friction and wear in metals that do not form hydrides (iron, copper, and some alloys based on these metals) and in hydride-forming metals (niobium, zirconium, and titanium) in gaseous hydrogen-containing environments and under the conditions of electrolytic hydrogenation are discussed.

Improvement of the Anticorrosion Properties of a Working Emulsion of Mine Hydraulic Systems

We seek new efficient corrosion inhibitors for the protection of steel rods of mine hydraulic cylinders with electric-arc sprayed coatings against corrosion in the FMI-RZh working emulsion contaminated with chloride ions. A significant deceleration of the corrosion fracture of 45 steel is detected after the addition of sodium silicate and benzyl benzoate to the emulsion. The inhibiting effect of benzyl benzoate can be explained by the adsorption of its polar molecules on the steel surface and by the formation of sodium benzoate as a result of the reaction with hydroxyl ions near the cathodic sections. Both inhibitors provide the efficient corrosion protection of the “45 carbon steel–electric-arc sprayed powder-wire coating” system in a 3% solution of sodium chloride under the conditions of leakage of the inhibited emulsion through the porous sprayed layer.

Quantum-Chemical Analysis of the Mechanism of Degradation of Binary Platinum Nanoclusters with Sulfur-Containing Compounds

We propose a quantum-chemical model of poisoning of binary Pt42Me13 platinum nanoclusters (where Me is a transition metal, namely, Fe, Co, or Ni) with core-shell structure by hydrogen sulfide and sulfur dioxide in media of low-temperature fuel cells. This model is based on the evaluation of the adsorption characteristics of interaction of H2S and SO2 molecules with the surfaces of nanoclusters. It is shown that their susceptibility to the formation of strong chemisorption bonds with H2S and SO2 molecules depends on the type of nanocluster core and the sites of adsorption on their surfaces. By using the quantum-chemical method of density functional, we establish the regularities of influence of the cores of binary nanoclusters of transition metals Fe, Co, or Ni on the geometric and energy characteristics of the adsorption of molecules. We also propose the mechanism of interaction of H2S and SO2 molecules with binary platinum nanoclusters based on the changes in the electronic properties of the surface platinum atoms or in the distribution of active adsorption centers on the surface of nanoclusters depending on the type of the core. The accumulated results confirm the prospects of the density functional method in the theoretical evaluation of the influence of chemical composition and the structure of binary nanoparticles on their properties in the reactions of low-temperature fuel cells.

Specific Features of the Cavitation-Erosion Fracture of D16T Alloy with Galvanic Nickel and Ni–B Composite Coatings in Corrosive Media

We study the influence of galvanic nickel and Ni-B coatings on the durability of D16T alloy under the conditions of cavitation. The specimens with and without coatings were tested immediately after their deposition and after vacuum annealing at 200 and 420°C. It is shown that heat treatment of the alloy with coatings of this kind increases its resistance to cavitation-corrosion wear in a 3% NaCl solution by a factor of 1.5 as compared with the untreated alloy. We reveal the abnormal character of changes in the electrode potential of the heat-treated Ni–B coating under the influence of ultrasound, which demonstrates its high heterogeneity and inability to form continuous passive films.

Inhibition of the Corrosion of Aluminum Alloy by a Composition of Ion-Exchange Pigments

It is shown that natural zeolites of the clinoptilolite-type modified with zinc cations serve as efficient corrosion inhibitor for aluminum alloys in the media of weakly acid atmospheric precipitations. The combination of Zn-zeolite with polystyrene-divinylbenzene resin modified with phosphate anions improves its protective properties due to the formation of corrosion-resistant films on the surfaces of alloys. Zinc-modified zeolite and its composition with phosphate-containing anion-exchange resins represent promising inhibiting pigments for paint-and-lacquer coatings on aluminum alloys.

Modeling of the corrosion-electrochemical processes on the metal–electrolyte interface

We develop a computer model of the electrochemical behavior of a metal–electrolyte contact boundary by using the quantum-chemical semiempirical method (PM6) and the molecular-dynamics method. We consider the evolution of the metal–medium systems and thoroughly study the thermodynamic and kinetic features of establishing the adsorption–desorption equilibrium for the Cu–electrolyte, Zn–electrolyte, Fe–electrolyte, and α-brass–electrolyte cluster systems. We compute the electrode micropotentials of copper, zinc, and α-brass, which satisfactorily agree with the experimental data.

Influence of incomplete annealing of titanium (a + β)-alloy and its welded joints on fatigue resistance and corrosion-fatigue resistance

We investigate the influence of incomplete annealing (675°C, 10 h) on fatigue, corrosion-fatigue, and high-temperature (up to 500°C) fatigue resistance of titanium (a+ β)-alloy Ti-5A1- 1.5V- IMo with nominal composition as well as its welded joints made by the electron-beam method. The effect of annealing depends on a totality of factors which dominate in different ways under fatigue fracture in air, in a 3% solution of NaCl, and high-temperature fatigue. Possible mechanisms of the influence of incomplete annealing on fracture of the titanium alloy and its welded joints are analyzed.