Surface Engineering and Applied Electrochemistry最新文献

The separation of oil–water emulsion with cellulose acetate membranes modified with a unipolar corona discharge at a voltage of 5–25 kV and time of 1–5 min was investigated. Decrease in the filter roughness after the impact of the corona discharge was determined using atomic-force microscopy. The results of X-ray diffraction analysis and of electrostatic field parameters’ measurements showed a decrease in crystallinity from 0.29 to 0.27 and the formation of positive charges on the surface of the sample, while the formation of a double electric layer according to dielectric spectrometry data was not detected. During the separation of the model oil–water emulsion, an increase in efficiency was revealed as 80 to 98% and the separation productivity from 15 to 35 dm³/(m² h) after treatment in the field of a unipolar corona discharge of cellulose acetate membranes, which is explained by a change in the supramolecular and chemical structure of the latter.

The effect of the phase composition of zinc-nickel alloy films electrodeposited on zinc-coated steel samples on their corrosion behavior was investigated. The alloys were electrodeposited from dilute ammonia-glycinate electrolytes. This type of electrolytes models the modified first bath in a rinsing system of the zinc plating line. It is shown that the galvanic displacement reaction at a level of 0.32 mA cm^–2 does not lead to a decrease of the adhesion of the alloy films to the zinc substrate. The best corrosion protection of a zinc coating is provided by a zinc-nickel alloy film, which additionally to the γ-phase also contains Ni or the amorphous β-phase. At the thickness of only approximately 1.5 μm, the Zn–Ni alloy shifts the corrosion potential of the galvanized steel by 100–150 mV in a positive direction and reduces the corrosion current density by 1.2–1.8 times.

Extensive chemical data for the corrosion of zinc in hydrochloric acid, sulphuric acid, sodium hydroxide and sodium chloride are available in the respective literature. However, studies of the corrosion of zinc in sulfamic acid are minimal. The present paper highlights the work on the corrosion behavior of zinc in sulfamic acid, which can be used as a pickling agent. Studies were carried out with three different acid concentrations: 0.1, 0.25, and 0.5 M at a temperature range of 303–323 K. The measurements were done by potentiodynamic polarization and electrochemical impedance spectroscopy techniques. In addition, scanning electron microscopy, energy dispersive X-ray, and atomic force microscopy techniques were applied for the surface studies. Spectroscopic techniques like X-ray diffraction analysis and atomic absorption spectroscopy were used to substantiate the corrosion process. Studies showed that the corrosion rate increased with an increase in the acid concentration and temperature. Surface morphology studies and spectroscopic studies confirmed enhanced deterioration of zinc at higher acid concentrations.

The effects of electrical conductivity of magnetic fluids both in the presence and absence of an external magnetic field are studied. It is shown that magnetic fluids based on magnetite (Fe₃O₄) magnetic nanoparticles coated with surfactant additive oleic acid contain current conducting ions that are formed because of oleic acid molecules involved in dissociation and electrochemical processes. The key role of the electrochemical reactions of oleic acid molecules on the surface of chemically active Cu electrodes in producing the injection conductivity is proved. The anisotropy of the electrical conductivity of the magnetic fluid in an external magnetic field is analyzed for chemically active and inert electrodes. The nonstationary ion processes in near-electrode layers, which determine the kinetics of magnetic nanoparticles and autowaves in thin magnetic fluid films, are interpreted.

The study of elemental composition of surface composites produced by electrospark alloying (ESA) of Type 45, 65G, and St3 steels with hard T15K6 and VK8 alloys and Type 45 and St3 steels (in the “steel-on-steel” mode) showed that the formed surface layers consisted of the ESA-modified steel substrate material by ~70%. The effects that the steel composition has on coefficients characterizing the transfer of the processing electrode material onto the substrate, surface roughness, microhardness, and wear resistance of resulting surfaces were investigated. It was found that the wear resistance of the composites is mainly determined by the nature of surface being processed and, to a much lesser extent, by the processing electrode material, surface roughness and microhardness.

Organic inhibitors are applied in the process of cleaning of steel oil pipelines using mineral acids. To reduce the cost of technology and improve the environment, it is proposed here to use nicotine contained in tobacco waste. A manufacturing technology for an inhibitor of the acid corrosion of steel oil pipelines has been developed by the authors earlier. Using an aqueous solution of benzoic acid, an inhibitors was obtained by extracting nicotine and related substances from tobacco waste: cigarette butts and cigarettes (Inhibitor 1), tobacco dust powder (Inhibitor 2) during the production of tobacco. The technology applies the opposite charge of benzoic acid to the charge of nicotine and its hydrotropic properties. The yield of nicotine during extraction from tobacco waste and the effectiveness of inhibitory protection of PSL-1 steel used for oil pipelines were investigated. Gas chromatography-mass spectrometry was used to study the composition of the inhibitors. Gravimetric and electrochemical methods were applied to determine its efficiency. The behavior of the polarization curves remained the same in the absence and in the presence of the inhibitors, but the curves shifted towards a lower log i in the presence of the inhibitors, which indicates that the inhibitor molecules slow down the corrosion process. The inhibitors act as a mixed type inhibitor, affecting both anodic and cathodic reactions. The efficiency of the inhibitor protection of PSL-1 steel was 92–96%. Corrosion inhibition results obtained by the weight loss method and electrochemical measurements are in good agreement.

To understand the corrosion of bent steel bars exposed to sand soils the physicochemical properties were tested and corrosion rates measurements were made in the laboratory as a function of the type of sand used in the production and reinforcement of concrete, of the exposure time, and of a drastic condition (a saturated sand soil simulating a wet concrete by moisture content). Some assumptions were involved in the investigation of activated concretes containing beach and/or pit sand to correlate the corrosion rate of a steel bar measured in laboratory conditions to that used in the field works. The paper presents four techniques to measure the corrosion rate; thus, a comparison of corrosion rates data via electrochemical and weight loss methods was carried out. The analysis of the obtained results suggested that the corrosion susceptibility was almost doubled for a bent steel bar exposed to the saturated pit sand after 74 days of exposure (the corrosion rate was found to be 0.136, 0.010, 0.025, and 0.026 mm/year by using linear polarization resistance, charge transfer resistance of the Tafel plots, and gravimetric measurements, respectively), in comparison with a not bent steel bar. The deviation of corrosion rates was attributed to a more conductive corrosion products resulting in a more active interface with respect to the experimental variables used in the electrochemical and weight loss measurements. The Tafel and weight loss measurements that were close between them must be useful in determining steel bars susceptibility to corrosion in drastic conditions simulating active concretes, to be applied to systems such as construction industries.

The present work describes the corrosion inhibition of mild steel—one of the metals widely utilized in industrial processes, in 0.25 M hydrochloric acid, using an amide substituted macrocyclic zinc phthalocyanine (TAZnPc). The corrosion inhibition efficiency was studied via potentiodynamic polarization technique and electrochemical impedance spectroscopy in a temperature range of 303 to 323 K, with the concentration of the inhibitor of 0.625–2.5 mM. The electrochemical study reveals that TAZnPc acts as mixed inhibitor, and the inhibition efficiency was found to increase with increasing the inhibitor concentration and decreasing temperature. The studied inhibitor showed the utmost inhibition efficiency of 86.48% at its optimum concentration of 5 mM. The excellent inhibitory performance is attributed to both the physisorption and chemisorption processes of adsorption of TAZnPc on the surface of mild steel. It was found that it followed the Langmuir adsorption isotherm. The results obtained by both potentiodynamic polarization technique and electrochemical impedance spectroscopy methods were in good agreement with each other. The surface morphology of the mild steel surface was studied by taking scanning electron microscope images, energy-dispersive X-ray spectroscopy and atomic force spectroscopy images without and with TAZnPc in 0.25 M HCl.