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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]

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]

• 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]