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Abstract: Single- and five-layer protective SiO2–Al2O3 coatings were deposited on an FeCrAl alloy. TEOS and TBA were used as precursors in a silica-rich sol. The deposited coatings improve the alloy''s resistance to high-temperature oxidation and to thermal shocks (the protection effectiveness is as high as 80%). As a result of diffusion from the core during annealing at 1200°C, the composition of the sample''s surface layer changes whereby the latter becomes enriched in aluminium. The composition of the forming aluminosilicates is situated between mullite and sillimanite (XPS measurements) and they are characterized by a small degree of crystallinity (XRD). [Copyright &y& Elsevier]

Abstract: Ternary Zn–Ni–Mo (1.2wt.% Ni, 4.5wt.% Mo) and Zn–Co–Mo (6wt.% Co, 4wt.% Mo) as well as reference binary Zn–Ni and Zn–Co alloy coatings were electrodeposited from citrate–sulphate baths. The influence of molybdenum on the surface morphology, structure, phase composition, corrosion and mechanical properties of the deposits was investigated. The XPS results revealed that the coatings with molybdenum contained appreciable amounts of Zn2+ inclusions, which is probably due to the low hydrogen evolution overpotential on the ternary alloys. The increase in the interfacial pH, promoted by intensive hydrogen evolution, causes the formation of oxidized zinc species which incorporate into the coating. The presence of MoO4 2− ions in the bath modified the morphology of the deposits — alloys with smoother surface were deposited. Polarization resistance measurements proved the beneficial influence of molybdenum on corrosion properties of examined alloy coatings. The presence of molybdenum improves the microhardness of the zinc-based alloys, but it has negative influence on the adhesion of the ternary coatings. [Copyright &y& Elsevier]

Abstract: Four-component Ni–W–P–ZrO2 composite coatings were electroless deposited. A bath containing aminoacetic acid as the agent complexing nickel ions, and sodium tungstate(VI) as the source of tungstate was used. It has been determined that as the bath''s pH increases (from 5 to 6) so does the rate of coating deposition while the phosphorus content in the coating decreases. Both an increase in the aminoacetic acid concentration and an increase in the sodium tungstate cause a reduction in the rate of deposition of the Ni–W–P–ZrO2 coating. Changes in the concentration of the two components in the bath result in a change in the composition of the coatings. When the concentration of the components is too high the bath loses its stability and a sediment precipitates itself. The ZrO2 content in the coating depends most on the amount of this powder in the suspension. [Copyright &y& Elsevier]

Abstract: One-, three- and five-layer SiO2–Al2O3 coatings were deposited on a FeCrAl alloy basis by the sol–gel method. Sols in which the molar ratio of tetraethoxysilan to aluminium tri-sec-butoxide was 1:1 and 1:3 were used. As the samples were being soaked at T =1200°C for t =700h the mass of the samples increased. Thermal shock (T =1200°C, 10,000 cycles) causes greater degradation of the surface than soaking at a constant temperature. The XPS and EDS results show that the composition of the top layer of the coatings changes during high temperature oxidation and thermal shock. The outward movement of aluminium cations results in surface enrichment with aluminium, particularly for the single-layer coatings. The measured energies of bonds Si 2p and Al 2p in the multilayer coatings indicate that a structure of aluminosilicates with a composition between that of mullite and that of sillimanite forms during sintering. [Copyright &y& Elsevier]

Abstract: Composite four-component Ni–W–P–ZrO2 coatings were electrolessly deposited from a bath with different concentrations of aminoacetic acid (glycine—the complexing agent), sodium tungstate(VI) and zirconium(IV) oxide at different pH values. Concentration distribution curves were determined for nickel–aminoacetic acid complexes as a function of the bath pH at different metal ion/complexing agent concentration ratios. It has been shown that the bath pH and the complexing agent concentration have the strongest effect on the composition and structure of the coatings. As the bath pH is lowered and the aminoacetic acid concentration is increased, the phosphorous content in the coating increases. In composite four-component Ni–W–P–ZrO2 coatings (similarly as in electroless two- and three-component nickel coatings), as the phosphorous content in the coating increases, the crystallinity of the coating decreases. Diffraction patterns deposited at pH 5 have only one peak corresponding to nickel: Ni(111) at 2Θ =44°. In the diffraction patterns at pH 8 one can observe sharp peaks for 5 crystalline planes: (200), (220), (311), (222) and dominant (111). After heat treatment at 400°C for 1h a nickel phosphide (Ni3P) phase appears (besides the crystalline nickel phase) in the coatings. Heat treatment also results in an increase in crystallite size from 1.5 to 2.0 to about 3.0nm. [Copyright &y& Elsevier]

The motion of ions in an electric field for solutions containing Cu2+ ions in the presence of 2-phosphonobutane- 1,2,4-tricarboxylic acid (PBTC), N-trismethylenephosphonic acid (NTMP) and N-(phosphonomethyl) imino-diacetic acid (PMIDA) was investigated using a capillary electrophoresis analyzer. Satisfactory agreement between the cation isotachophoretic determination results and the results calculated from the protonation constants of the relevant ligand species and the stability constants of copper complexes was obtained. The research results can be useful for the electrokinetic method of removing copper from soil. [ABSTRACT FROM AUTHOR]

Abstract: Electroless binary Ni–P and ternary Ni–W–P alloy coatings and electroless composite (Ni–P–ZrO2 and Ni–P–W–ZrO2) nickel coatings were deposited. Baths with aminoacetic acid as the complexing agent were used. ICP measurements showed that the P content depending on the type of coating is in a range of 4.7–6.3 wt.% (at pH=6, t =75 °C). The tungsten content is around 1–2 wt.%. SEM examinations show that the electroless Ni–P coating has the most fine-grained structure. Grains in the form of microspheroids 20 μm in size are characteristic of the Ni–P–ZrO2 coating. X-ray diffraction patterns show that for all the obtained coatings peak Ni(111) located around 2θ =44° is the most intensive. After the coatings are heat treated at 400 °C for 1 h the peak becomes even sharper. The heat treatment results in a nearly double increase in crystallite size. The quaternary coatings'' abrasion resistance is determined by the second-phase (ZrO2) particles present in them. [Copyright &y& Elsevier]

Graphical abstract Highlights • Annealing Ni−Mo alloy coating at 200 and 400 °C increases the deposit hardness. • Ni−Mo coatings heated at 400 and 600 °C become brittle. • Heating Ni−Mo deposit at 400 °C significantly improves its corrosion resistance. • Annealing Ni−Mo deposit affects thickness and composition of passive film. Abstract Ni−26 wt% Mo alloy coatings were annealed for 1 h in an air atmosphere at temperatures of 200, 400 and 600 °C. The influence of heat treatment on the structure and the mechanical and corrosion properties was investigated. It was found that the coating microhardness increased significantly after annealing at 200 and 400 °C. The results of the scratch test revealed that. Ni−Mo alloys heated at higher temperatures (400 and 600 °C) were characterized by lower adhesion and more brittle nature in comparison to the as−deposited coating and the coating heated at 200 °C. Annealing at 400 °C led to a significant improvement of corrosion resistance of the coating. This was the consequence of an increase in the thickness of an oxide layer formed on the coating surface. When exposed to a corrosive solution, the protective ability of the oxide layer deteriorated, which was followed by a systematic drop of polarization, charge transfer, and pore resistance. XPS analysis revealed that the surface layer of the as−deposited coating and the coating heated at 200 °C was mainly composed of NiOOH and Ni(OH) 2 and contained higher amounts of Mo in comparison to the deposit bulk. The surface layer of coatings heated at higher temperatures was composed of NiO and contained only small amounts of Mo. [ABSTRACT FROM AUTHOR]

Ni–Mo–ZrO 2 composite coatings were produced by electrodeposition technique from citrate electrolytes containing dispersed ZrO 2 nanopowder. The influence of deposition parameters i.e. concentration of molybdate and ZrO 2 nanoparticles in the electrolyte, bath pH and deposition current density on the composition and surface morphology of the coating has been investigated. The structure, microhardness and corrosion properties of Ni–Mo–ZrO 2 composites with different molybdenum and ZrO 2 content have been also examined. It was found that ZrO 2 content in the deposit is increased by rising the nanoparticles concentration in the plating solution up to 20 g dm −3 . An increase in molybdate concentration in the electrolyte affects negatively the amount of codeposited ZrO 2 nanoparticles. The correlation between the deposition current efficiency and ZrO 2 content in the composite coating has been also observed. A decrease in deposition current efficiency leads to deposition of Ni–Mo–ZrO 2 composite with low nanoparticles content. This may be explained by formation of higher amounts of gas bubbles on the cathode surface, which prevent the adsorption of ZrO 2 nanoparticles on the growing deposit. The XRD analysis revealed that all the studied Ni–Mo–ZrO 2 coatings were composed of a single, nanocrystalline phase with FCC structure. It was found that the incorporation of ZrO 2 nanoparticles into Ni–Mo alloy matrix affects positively the microhardness and also slightly improves the corrosion properties of Ni–Mo alloy coating. [ABSTRACT FROM AUTHOR]

The changes in composition of the corrosion products of electrodeposited ternary Zn–Co–Mo alloy coatings on AISI 1015 steel during exposure to 0.5 mol dm −3 NaCl solution were investigated. XPS studies demonstrated that at the initial stage of corrosion on the surface of Zn–Co–Mo coating zinc hydroxide layer is formed. Hydroxyl groups react with chloride and carbonate ions which lead to the formation of zinc hydroxy carbonates and zinc hydroxy chlorides. The share of these compounds in the oxidation products is initially large. However, with time zinc hydroxy compounds slowly changes to zinc oxide, which is more stable corrosion product. It was estimated that after 24 h of exposure to NaCl solution nearly 60% of zinc detected on the surface of Zn–Co–Mo coating was present in the ZnO form, 18% in the form of zinc hydroxy chloride, and more than 21% as zinc hydroxy carbonate. XPS analyses revealed that the amount of zinc hydroxy chloride increases as the exposure time lengthens and it is significantly higher than at the surface of binary Zn–Co coating. The presence of crystalline zinc chloride hydroxide as a stable product of corrosion of ternary Zn–Co–Mo alloy coating in a 0.5 mol dm −3 NaCl solution was confirmed by XRD analysis. According to XRD and FTIR other zinc corrosion products like: ZnO, Zn(OH) 2 and Zn 5 (CO 3 ) 2 (OH) 6 were also present. The results of XPS and EIS measurements allow us to assume that in the presence of Mo in the alloy, on the surface of ternary Zn–Co–Mo alloy (3.4 wt.% Co, 2.7 wt.% Mo) coating more zinc hydroxy chloride is formed, which favors higher corrosion resistance of this coating. [ABSTRACT FROM AUTHOR]

Abstract: Chromium-free conversion coatings were deposited from a bath containing potassium hexafluorotitanate(IV). The substrate was electrogalvanized carbon steel. The obtained coatings had a microspheroidal structure and were homogenous. An XPS analysis showed that the coatings were composed of: oxides, hydroxides, phosphates, carbonates and fluorocompounds. As part of this study, the influence of coating deposition time on the surface morphology, chemical composition and physicomechanical properties of the samples was examined. DC polarization measurements, electrochemical impedance spectroscopy and neutral salt spray tests showed that the investigated Cr-free coatings markedly increase the corrosion resistance of electrogalvanized steel in a chloride environment. [Copyright &y& Elsevier]

ABSTRACT Electroless nickel-phosphorous plating is a technique often employed in preparation of protective, decorative, and functional coatings. Several feasible mechanisms are discussed in the literature. The influence of process parameters on metal coating deposition is analyzed and described. Nevertheless, some basics of the process and the fundamental aspects of plating still not explained. A number of research groups make an effort to provide a description of the process with a physical model. The aim is to design a theoretical model that could be valid under operating conditions on a practical scale. This work gives a short review of the published data on the mechanism and kinetics of the electroless Ni-P deposition process. The review also touches a novel approach-proposition to analyze data using artificial intelligence tools. [ABSTRACT FROM AUTHOR]

Ni-P matrix, ternary Ni-W-P and Ni-P-ZrO2 coatings, and quaternary Ni-W-P-ZrO2 coatings were deposited using electroless method from a glycine bath. Their corrosion resistance was evaluated by electrochemical impedance spectroscopy (EIS) for various immersion times in a 3.5% NaCl solution. From among the investigated coatings, the ternary Ni-W-P coatings show the highest resistance to corrosion in the first hour of exposure to the 3.5% NaCl medium. An addition of ZrO2 adversely affects the performance of both the Ni-P coatings and the Ni-W-P coatings. For all the coatings, including the ones containing tungsten, a marked decrease in pore resistance (Rpor) over time is observed. This means that their corrosion resistance and capacity to protect the substrate decline. On the other hand, after 24 h immersion in the 3.5% NaCl solution the Ni-W-P coating shows the highest low-frequency impedance modulus (| Z|f = 0.01 Hz). As regards corrosion resistance, the Ni-P coatings and the Ni-W-P coatings perform best. [ABSTRACT FROM AUTHOR]

La1−xAgxFeO3 (x = 0.05–0.25) perovskites deposited on a honeycomb-shaped monolithic metallic support were used as catalysts for the total oxidation of hydrocarbons. Monolithic catalysts were prepared by washcoating honeycomb substrates with lanthanum-stabilized γ-Al2O3, on which La1−xAgxFeO3 was deposited. Catalysts with La1−xAgxFeO3 perovskites show higher activity for methane oxidation at x ≥ 0.05 and hexane oxidation at x ≥ 0.1 than LaFeO3 catalyst. The perovskite catalysts were characterized by XRD, XPS, SEM, TEM, TPR-H2, O2-TPD and BET specific surface area measurement. Ag forms solid solutions with the La1−xAgxFeO3 perovskite lattice for x = 0.05–0.1. In La1−xAgxFeO3 perovskites (x ≥ 0.1), Ag0 particles with average crystallite sizes from 31 to 41 nm were also identified. When Ag is introduced into the LaFeO3 perovskite, both the changes occurring after some Ag is incorporated into its structure and the presence of large crystallites of metallic silver contribute to the catalysts' activity increase. [ABSTRACT FROM AUTHOR]

Abstract This study presents an analysis of the impact of the oxide layers, prepared by means of laser radiation in ambient air with different process parameters, on the morphology, corrosion resistance and adhesion properties of titanium grade 2. The samples were irradiated in and out of the focal plane, using a commonly-available fiber laser (Yb:glass) system. The microscopic examination, colorimetry, roughness, chemical Raman analysis, electrochemical tests (electrochemical impedance spectroscopy) as well as adhesion, wettability and scratch-tests were conducted. The study has shown that laser oxidation, depending on the choice of process parameters, can contribute to both the improvement and deterioration of the surface quality, including the size and amount of microcracks, other defects or heterogeneities, roughness, and adhesion. The samples manufactured in the focal plane exert a higher corrosion resistance, higher adhesion and lower roughness, compared to those irradiated out of the focal plane. The aim of this study was to broaden the knowledge about the nature and influence of laser-induced oxidation in and out of the focal plane on selected properties of oxide layers. Highlights • Samples treated in the focal plane exert increase of the corrosion resistance. • Laser-induced coatings exert a hydrophilic character (water contact angle <90°). • Samples treated in the focal plane exert decrease in roughness. • Laser-induced coatings exert a high adhesion to the substrate. [ABSTRACT FROM AUTHOR]

The passive layer on Zn Fe Mo coating (7.6 at.% Fe, 1.6 at.% Mo) became damaged in 0.5 M NaCl solution, as shown in ionic current density maps that were observed during 10 h of exposure. The ZnO and Zn(OH) 2 slowly transformed into Zn 5 (OH) 6 (CO 3 ) 2 and Zn 5 (OH) 8 Cl 2 ·H 2 O. At the same time, MoO 2 transformed to MoO 3 and MoO(OH) 2 . The barrier properties of the layer of corrosion products deteriorated so the charge transfer resistance decreased from 13 to 7.4 kΩ cm 2 and the double layer capacitance increased from 4.5 to 62 μF cm –2 after 0.5 h and 10 h exposure, respectively. [ABSTRACT FROM AUTHOR]

Ternary Zn–Fe–Mo alloy coatings electrodeposition in a sulphate bath with tri-sodium citrate in the pH range 4.8–6.0 was studied. The increase of the plating bath pH from 4.8 to 6.0 leads to the iron content increase from 1.5 up to 7.9 wt% and it is accompanied by a significant decrease in the current efficiency from 76 to 51%. It was demonstrated that molybdenum co-deposition starts at pH > 4.8, because binary Zn–Fe alloy coating without a significant amount of molybdenum was obtained from the plating solution at pH 4.8. The Mo content increases from 0.8 wt% at pH 5.1 to 2.7 wt% at pH 5.7 and 6.0. X-ray diffraction analysis as well as anodic linear sweep voltammetry measurements showed that within the considered plating solution pH range molybdenum modifies zinc microstructure to a very large extent. The deposited at pH 5.4–6.0 Zn–Fe–Mo coatings contain a solid solution of iron and molybdenum in zinc and probably FeZn x phase, where 6.67 < x < 13. Potentiodynamic polarization revealed that the deposited at pH 5.7 and 6.0 Zn–Fe–Mo coatings are characterized by a significantly lower corrosion rate in 0.5 mol dm − 3 NaCl solution. This was confirmed by an electrochemical impedance spectroscopy test, where Zn–Fe(7.9 wt%)–Mo(2.7 wt%) alloy coating reached the highest resistance of charge transfer reaction during 24 hours of exposure to NaCl solution. [ABSTRACT FROM AUTHOR]

Ternary Zn–Fe–Mo alloy coatings, as a potential replacement for zinc coatings, were deposited from a citrate-sulphate solution. It has been shown that by varying the concentration of Na 2 MoO 4 in the plating bath in a range of 0.0025 − 0.05 mol dm −3 it is possible to obtain coatings containing from 0.4 to 2.7% at. Mo and from 2.8 to 7.6% at. Fe. It has been proved that molybdenum and iron do not form intermetallic phases with zinc. However, at higher Mo and Fe content the presence of oxidized molybdenum compounds in the coatings is possible. Among them the most probably are: FeMoO or Mo 5 O 7 (OH) 8 . EIS measurements revealed that the ternary Zn–Fe–Mo alloy (7.6% at. Fe, 2.4% at. Mo) coating offer better corrosion resistance during 24 hours of exposure in NaCl solution than the Zn–Fe (1.7% at.) binary coating and pure Zn coating. The good protective properties of Zn–Fe–Mo coatings are due to the presence of a relatively thin (approx. 7 nm) passive layer enriched in molybdenum oxides and hydroxide compounds. [ABSTRACT FROM AUTHOR]

Ni-P\nano-ZrO2 composite coatings were obtained on the AISI 304 steel substrate by the electroless method from a bath containing dodecyltrimethylammonium bromide (DTAB). This cationic surfactant prevents ZrO2 agglomeration in the bath and affects the ZrO2 content in the coating, hence it alters functional properties of the coatings. It has been found in this study that corrosion resistance of the composite coatings depends on the surfactant concentration in the bath.The estimation of corrosion resistance was carried out by electrochemical impedance spectroscopy. The degree of the sample surface coverage with corrosion products was determined by the machine vision method.The coating obtained from the 0.88 g/dm3 DTAB solution showed the best protective properties. The machine vision method was shown to be an effective complementary tool to evaluate protective properties of the coatings. [ABSTRACT FROM AUTHOR]

Ternary Zn–Co–Mo alloy coatings were deposited from a citrate–sulphate bath. In a pH range of 5.5–5.9 the coatings contained 2.3–3.6 wt.% molybdenum and 3.4–3.7 wt.% cobalt. DC and EIS measurements revealed that in the course of 24 h exposure to NaCl solution the corrosion resistance of Zn–Co–Mo alloy coatings was higher than that of Zn and Zn–Co coatings. On the basis of XRD, ALSV and XPS studies it can be stated that the beneficial effect on the corrosion resistance of Zn–Co–Mo coatings has a passive layer composed of: Zn(OH) 2 , ZnO, Mo(IV) oxide and hydroxide and a small amounts of Co 3 O 4 . [ABSTRACT FROM AUTHOR]