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Hydroxyapatite (HA) bioactive film is a standard surface modification method for biodegradable Mg alloys. However, the corrosion resistance of HA film prepared before was mediocre, and the preparation process was complicated. In this study, hydroxyapatite film was prepared for the first time on layered double hydroxides (LDHs) coated Mg alloy by hydrothermal method. The structure and composition of LDHs and HA films were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS), Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The corrosion resistance and immersion behavior of the films in simulated body fluid (SBF) were investigated by using potentiodynamic polarization curve, electrochemical impedance spectroscopy (EIS) techniques. The effects of different pH and calcium to phosphorus molar ratios (Ca/P ratios) of HA hydrothermal solution were investigated. The experimental results show that HA films appear in petal-like, filamentous and flower-like. The corrosion resistance of the film first increases and then decreases with the pH from weak acid to alkaline. With the increase of the Ca/P ratio, the film is gradually denser, and the protective effect is enhanced. The immersion test results show that after 7 days of immersion, the impedance modulus of the composite film is about 5 × 103 Ω·cm2, which is ten times higher than the single LDHs film. The effects of the pH and Ca/P ratio of the HA hydrothermal solution on the preparation of HA film are simply explained by thermodynamic theory. The Mg-LDHs-HA composite film provide a corrosion protection barrier for Mg substrate and HA film is biologically active. The barrier effect and the mineralization behavior provide a better corrosion protection for Mg substrate. [Display omitted] • HA film was prepared for the first time on LDHs-coated Mg alloy. • The preparation method of the composite film is simple. • Mg-LDHs-HA composite film exhibits durable corrosion resistance in SBF solution. • The effects of pH and Ca/P ratio were explained using thermodynamic theory. [ABSTRACT FROM AUTHOR]

ZnO@ZIF-8 films were prepared on Q235 steel surface through solvothermal reaction by pre-electrodepositing ZnO films and modified with stearic acid (SA). The surface morphology, elements content, crystal structure and chemical structure of films were studied by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The wettability of films was measured by water contact angle meter. The corrosion behavior of films was tested by Electrochemical tests. ZnO films show hexagonal nanotubular morphology, having the best compactness and corrosion resistance at deposition current density of 2.3 mA/cm2 with the protection efficiency of 90.11%. After solvothermal reaction, ZIF-8 grains are formed and clad ZnO nanotubes, forming a contact film to prevent corrosive ions attacking steel efficiently. ZnO@ZIF-8 films have the best compactness and corrosion resistance at Zn2+ concentration of 0.06 mol/L with the protection efficiency of 99.83%. But the corrosion resistance of ZnO@ZIF-8 film declines quickly for the water molecules can get inside the film and destroy the bond between ZIF-8 grains. Thus, SA was grafted to ZnO@ZIF-8 film to enhance its hydrophobicity. After SA modification, the protection efficiency reaches 99.99% and maintains at 95.29% after 14 days immersion in the solution of 3.5 wt.% NaCl. [Display omitted] [ABSTRACT FROM AUTHOR]

The nickel-ferric layered double hydroxides (NiFe-LDHs) film which are commonly used as catalysts was fabricated on Q235 steel in-situ via two-step hydrothermal method. And the superhydrophobic NiFe-LDH-PFDTES film was obtained by 1 H, 1 H, 2 H, 2 H-perfluorodecyltriethoxysilane (PFDTES) modification. To a certain extent, the application of NiFe-LDHs has been broadened. The structure and composition of NiFe-LDHs film and NiFe-LDH-PFDTES film were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS), and Fourier transform infrared (FT-IR). The wettability of films was analyzed by water contact angle testing. And the corrosion resistance of NiFe-LDHs and NiFe-LDH-PFDTES film in 3.5 wt% NaCl solution were measured by using potentiodynamic polarization curve and electrochemical impedance spectroscopy (EIS) techniques. The results show that NiFe-LDHs and NiFe-LDH-PFDTES film were successfully prepared on the surface of Q235 steel. By adjusting the preparation conditions, the NiFe-LDH-PFDTES film with optimal corrosion resistance was prepared in the condition containing the hydrothermal solution concentration is 1 unit and hydrothermal time for 6 h. The hydrophobicity changes little with the hydrothermal parameters, and all reach the state of superhydrophobic, the contact angle is greater than 150°, the sliding angle is less than 1°. For the superhydrophobic film, NiFe-LDHs has excellent synergy with PFDTES, covering of an "air film" on the rough structure of LDHs, blocking the solution from contact with the substrate, thereby providing corrosion resistance. NiFe-LDH-PFDTES film exhibits much better corrosion protective performance than NiFe-LDHs film in 3.5 wt% NaCl solution, the impedance modulus is increased about 4–5 orders of magnitude compared with Q235 steel, and the highest protection efficiency can reach 99.99%. [Display omitted] [ABSTRACT FROM AUTHOR]

Microstructure evolution of the nickel-aluminum bronze alloy was studied by heat treatment, including annealing, normalizing, quenching and aging. The microstructure was refined and homogenized after quenching or quenching/aging at 450 ℃, which can eliminate selective phase corrosion effectively. Compared with the current production process, static corrosion rate reduced about 50%, due to the rapid formation of a protective film. In addition, cavitation corrosion rate reduced by a factor of 4.9 and 7.9 for the quenched and quenched/aged at 450 ℃ samples, respectively. This can be attributed to the improved hardness and weakened synergy between corrosion and mechanical attack. [ABSTRACT FROM AUTHOR]

The gradient Ni-Cu layer on nickel aluminum-bronze alloy was obtained by the thermal diffusion process. The corrosion resistance was improved due to the formation of protective film, consisted of Ni(OH) 2 and Cu 2 O. Although the Ni-Cu layer exhibited local corrosion with uniform corrosion and pitting corrosion simultaneously during the immersion test, the pitting growth was depressed because of the gradient distribution of Ni and Cu. The relieving driving force for galvanic corrosion between outer passive layer and bare Ni-Cu in the pitting was the main factor, which was caused by the decreasing interface potential drop. [ABSTRACT FROM AUTHOR]

Co-Diamond Like Carbon (Co-DLC) nanocomposite film is considered as a potential biosensor material owing to its various properties such as corrosion resistance and superparamagnetic property. In this work, by adjusting the substrate temperature from 298 to 673 K, the microstructure of Co-DLC nanocomposite film is modulated. With the rising of the substrate temperature, Co particle size increases from 3.8 to 6.4 nm and the crystallinity is improved; the sp2/sp3 ratio of the film is increased, which reduces micropores for penetration of corrosive entities. As a result, the saturation magnetization of superparamagnetic property is enhanced by 2.4 times from 0.11 to 0.26 T, and the total corrosion resistance of the film is enhanced by more than 300 times from 3.5 × 104 to 1.1 × 107 Ω·cm2. By establishing the mechanism model, the improvement of magnetic properties and corrosion resistance caused by microstructure controlling in Co-DLC nanocomposite film is reasonably explained. [Display omitted] • Large Co particle size and high crystallinity induced by high substrate temperature • Reduced micropores for corrosive entities penetration by increased sp2 clusters • 2.4-time superparamagnetic magnetization and 300-time corrosion resistance realized • High magnetic properties and corrosion resistance achieved simultaneously [ABSTRACT FROM AUTHOR]

Nickel alloy 690 (Ni690) were fabricated by wire arc additive manufacturing (WAAM) with three kinds of TiC particles adding contents (no TiC addition, 0.5 wt% TiC, 1.0 wt% TiC) based on cold metal transfer (CMT) technology. The effects of TiC particles adding content on the microstructure, mechanical properties and corrosion resistance were investigated. After adding 1.0 wt% TiC particles, the average length of the γ grains decreased from 301 ± 61 µm to 114 ± 15 µm and the structure of grains changed from columnar dendrite into equiaxed dendritic at the top of each layer, which is results of the heterogeneous nucleation and increase of constitutional supercooling caused by TiC particles. The difference between horizontal and vertical mechanical properties of WAAM Ni690 component disappeared because the heterogeneous nucleation caused by TiC particles prevented the epitaxial growth. The ultimate tensile strength of the WAAM 1.0TiC-Ni690 component reached 590 MPa in both directions, which increased 10 % compared with no TiC addition. The improvement of mechanical properties was owing to the grain refinement and the formation of reinforcing TiC/(Ti, Nb)C second-phase particles. The potentiodynamic polarization tests showed that the improved corrosion resistance with the increased content of TiC particles. The electrochemical impedance spectroscopy (EIS) tests results showed that due to the refined γ columnar grains providing more nucleation sites, a denser and thicker passive film was formed, which improved the corrosion resistance. The composition of the passive film was analyzed by X-ray photoelectron spectroscopy (XPS). The results reflected the more content of oxides and hydroxides of Cr in the passive film of WAAM 1.0TiC-Ni690 sample represented the denser passive film and better corrosion resistance. • Nickel alloy 690 (Ni690) were fabricated by wire arc additive manufacturing (WAAM) with different kinds of TiC particles adding contents. The TiC particles improved the mechanical properties and corrosion resistance • With the addition of TiC particles, the anisotropy in strength of WAAM Ni690 component disappeared for heterogeneous nucleation and the reinforcing TiC/(Ti, Nb)C particles improved the strength of WAAM 1.0TiC-Ni690 component in both directions reaching 590 MPa. • The refiner columnar γ grains offered more nucleation sites on the grain boundaries for the formation of thicker passive film. The more content of oxides and hydroxides of Cr in the passive film of WAAM 1.0TiC-Ni690 component represented the denser passive film and better corrosion resistance. [ABSTRACT FROM AUTHOR]

Various strategies have been developed to fabricate mechanical robust superhydrophobic membranes on the original substrates. However, for superhydrophobic coatings that have to be homologous to the inherently fragile substrate, their mechanical stability problems have not been satisfactorily solved. Herein, we prepared three hierarchical superhydrophobic Cu coating via facile pulse electrodeposition with microstructure size of 10–15, 30–40, and 60–70 µm, respectively. The resulting superhydrophobic coatings simultaneously exhibit excellent self-cleaning, mechanical robustness, and corrosion resistance. A hydrophobic mechanism suitable for worn superhydrophobic surfaces was proposed, which can well analyze the influence of microstructure changes on wettability. Moreover, these three coatings can withstand 15, 50, and 100 cycles of sandpaper abrasion, respectively, as the size of the microstructure increases. The results demonstrate a size effect of microstructure, which means surfaces with larger-sized microstructures can better maintain their superhydrophobicity under mechanical damage. Our findings offer a reference for improving the mechanical robustness of other superhydrophobic coatings that are homologous to the substrate. [Display omitted] • Three superhydrophobic Cu coatings with mechanical robustness, self-cleaning, and corrosion resistance were fabricated. • A hydrophobic mechanism suitable for worn superhydrophobic surfaces was proposed. • The size effect of microstructure on resisting mechanical damage was investigated. • A strategy in improving the mechanical stability of fragile coatings homologous to the substrate was found. [ABSTRACT FROM AUTHOR]

[Display omitted] • A superhydrophobic hierarchical Cu cone-flower structure was fabricated. • Correlation of roughness skewness and void volume ratio to wettability was studied. • A new hydrophobic model was proposed to explain effect of structural parameters. Superhydrophobic films have been successfully prepared on various substrates by finely controlling surface micro/nanostructure's roughness and reducing surface energy. However, there is no unified conclusion about the correlation of surface roughness and 3D volume parameters to wettability. Herein, we fabricated a superhydrophobic film composed of hierarchical Cu cone-flowers via facile one-step pulse electrodeposition with a 30% duty cycle for 20 min. Based on this film, the relationship between roughness/volume parameters and hydrophobicity was well studied. The resulting cone-flower film exhibits excellent corrosion resistance and self-cleaning properties due to a high water contact angle (WCA) of ~160° and a low sliding angle (SA) of ~3°. The large roughness skewness (Rsk = 0.7–1.3) and void volume ratio (Vvc/Vmc > 1.5) are shown to be more desirable to achieve superhydrophobic surfaces. Moreover, a new hydrophobic model is proposed to explain the above results, which means that the nanoscale air cushions share most of the gravity of water droplets to help microscale air cushions closer to the Cassie state. Further experiments by adding or destroying the nanostructures to observe the change of hydrophobicity well verified our conjecture. [ABSTRACT FROM AUTHOR]

To realize the potential application of the Co-DLC magnetic nanocomposite film in biosensor, it is necessary to obtain superparamagnetic property with high magnetization and good corrosion resistance in Co-DLC film. However, the cobalt carbide produced in the traditional preparation process will deteriorate the superparamagnetic property of Co-DLC film. To suppress the formation of cobalt carbide, strong magnetic target co-sputtering has been induced to prepare the Co-DLC nanocomposite films in this work. The results show that the cobalt particles are distributed in the amorphous DLC matrix. Most of cobalt exists in the form of metallic cobalt, and no cobalt carbide is formed during the film deposition process. The films maintain superparamagnetic property, which fits well with the Langevin equation. The saturation magnetization of the Co-DLC films increases with the increase of cobalt content, which reaches 0.068 T at cobalt content of 36 at. %. Meanwhile, when the cobalt content increases, the degree of graphitization of the film increases, which leads to a decrease in corrosion resistance of the film. Whereas, the polarization resistance of Co-DLC nanocomposite film is still higher than 1.03 × 105 Ω·cm2. The Co-DLC nanocomposite films with cobalt content between 29 and 36 at. % exhibit superparamagnetic property with high saturation magnetization and corrosion resistance. [Display omitted] • The method of strong magnetic target co-sputtering inhibits the formation of cobalt carbides in Co-DLC films successfully. • These films maintain superparamagnetic property, which is fitted well with Langevin equation. • The corrosion resistance of the Co-DLC film is above 10 times higher than that of the cobalt film. • The films with cobalt content between 29 and 36 at. % exhibit both high saturation magnetization and corrosion resistance. [ABSTRACT FROM AUTHOR]

• PASP-Zn films were constructed on Q235 steel by coordination self-assembly. • PASP-Zn films can improve the corrosion resistance of Q235 steel significantly. • Corrosion resistance is related to PASP/Zn ratio, pH value and assembly time. • The assembly and protection mechanism of PASP-Zn films are proposed. In this work, an economical and environmentally friendly polyaspartic acid-zinc (PASP-Zn) film was successfully prepared on the surface of Q235 steel by coordination self-assembly, and the preparation conditions of PASP-Zn film were optimized by single factor method. The surface morphology and thickness of PASP-Zn film were investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM), and the structure and composition of PASP-Zn film were determined by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The corrosion resistance of PASP-Zn film on Q235 steel in 3.5wt % NaCl solution was analyzed by electrochemical impedance spectroscopy (EIS) and polarization curves. The results show that PASP film and PASP-Zn film are successfully prepared on the surface of Q235 steel, and the single PASP film is self-assembled monolayers with thin thickness and loose structure. Whereas PASP-Zn film shows a rough morphology, accompanied by appearance of a large amount of nanoparticles, and the thickness of PASP-Zn film is about 98.0 nm. PASP-Zn film exhibits much better corrosion protective performance than PASP film in 3.5 wt % NaCl solution, and the highest protection efficiency can reach 94.48 %. The excellent coordination ability between PASP and zinc ions can effectively improve the compactness and thickness of PASP-Zn film, and prevent the corrosive ions from contacting the Q235 steel surface. By adjusting the preparation conditions, a PASP-Zn film with optimal corrosion resistance was prepared in the film-forming solution containing PASP/Zn ratio of 1:8 and pH value of 5.0 for 30 min. [ABSTRACT FROM AUTHOR]

A supersaturated solid solution layer with a fine-grained size of 30–50 μm was formed on a nickel–aluminum bronze via laser surface quenching technology, and its corrosion resistance was improved by 42.6%, which was attributed to the homogenized element distribution and the formation of a more protective film during corrosion process. • The microstructure of as-cast NiAl bronze was refined by laser surface quenching. • Selective phase corrosion was eliminated for the uniform element redistribution. • Corrosion rate decreased 42.6% after laser surface quenching. • Enhanced corrosion resistance was ascribed to formation of a more protective film. Laser surface quenching technology was utilized to modify the surface microstructure of as-cast nickel-aluminum bronze. A supersaturated solid solution layer with a fine-grained size of 30–50 μm was formed, and its corrosion behavior was studied by electrochemical measurements and long-term immersion corrosion test. It was found that laser surface quenching homogenized the distribution of elements in the constituent phases and eliminated the selective phase corrosion. Due to the formation of a more protective film on laser quenched NAB alloy, the corrosion rate reduced about 42.6% compared with that of as-cast NAB alloy. [ABSTRACT FROM AUTHOR]

• Cavitation erosion behaviours of surface chromizing layer were investigated. • The pitting and galvanic corrosion resistances were enhanced due to high Cr concentration. • Excellent combination of surface hardness and surface toughness was obtained. • The cavitation erosion mechanism of chromizing layer was proposed. To enhance the cavitation erosion resistance of industrial components, two types of Cr-rich diffusion layers were fabricated on 316L stainless steel through pack chromizing process. The chromizing layer before post heat treatments exhibited poor cavitation erosion performances, which could be ascribed to its high brittleness and the galvanic corrosion. The chromizing layer after post heat treatments showed the excellent cavitation erosion resistance with a 3.97 times lower erosion mass loss compared with that of 316L stainless steel. The corrosion resistance was significantly improved with a 12.5-time lower free corrosion current density than 316L stainless steel, and the surface mechanical properties of chromizing layer also exhibited great combination of hardness and toughness. Therefore, the higher cavitation resistance was attributed to the better corrosion and mechanical performances originating from the more homogeneous microstructure after post heat treatments. [ABSTRACT FROM AUTHOR]