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Micro-arc oxidation (MAO) is widely applied to improve the corrosion resistance of Mg alloys by forming a ceramic passivation film on their surface. The high cohesive strength and randomly distributed micro-porous structure of MAO films have significantly expanded their operation scope, serving as the base or bonding layer for composite or multi-functional coatings. However, mechanical scratches or impacts during installation and service periods can damage the protective performance of MAO films, leading to local corrosion or the rapid loss of mechanical integrity in Mg alloys. Therefore, the development of MAO coatings with self-healing properties has been extensively studied in recent decades. This paper aims to illustrate the gaps between the anti-corrosion characteristics and self-repairing mechanisms dependent on the oxide composition or porous structure of MAO films. The progress in preparation and the principle of inhibitor loading in self-healing functional MAO-based composite coatings are summarized, and future directions are highlighted. [ABSTRACT FROM AUTHOR]

[Display omitted] • Investigation of corrosion mechanism assisted by first-principle calculation. • Correlation between interface properties and electrochemical stability. • Reinforcement on interface stability by TiC/TaC and TaC/C contacting. • A low corrosion current density of 0.28 μA cm−2 for the TaC/TiC/TaC/C coating. In this study, first-principle calculation is used to investigate the TiC (1 1 1)/TaC (1 1 1) interface in terms of surface energy, work function, adhesion energy, and electronic structure. Compared with TaC (1 1 1), the TiC (1 1 1) surface shows a higher surface energy and a lower electronic work function. The surface passivation of TiC can be achieved by covering the TaC layer. Besides, the interface bonding configuration of TiC (1 1 1)/TaC (1 1 1) that relates to corrosion resistance is studied in detail. In experimental verification, a set of TiC-based coatings are investigated by potentiodynamic polarization, potentiostatic polarization, and impedance. Compared with pure TiC and TiC/C coatings, the TaC/TiC/TaC/C structure exhibits the lowest corrosion current density of 0.28 μA cm−2 and the lowest corrosion tendency. SEM observation also reveals its minimal morphological damage after potentiostatic polarization. The modified multilayer coating presented in this work is successfully used as the protecting structure of stainless-steel bipolar plate, which may be of great significance to the light weight metallic bipolar plate in proton exchange membrane fuel cells. [ABSTRACT FROM AUTHOR]

Ti6Al4V titanium alloy has been widely used as medical implant material in orthopedic surgery, and one of the obstacles preventing it from wide use is toxic metal ions release and bacterial implant infection. In this paper, in order to improve corrosion resistance and antibacterial performance of Ti6Al4V titanium alloy, ZnO doped tantalum oxide (TaxOy) multilayer composite coating ZnO-TaxOy/TaxOy/TaxOy-TiO2/TiO2/Ti (ZnO-TaxOy) was deposited by magnetron sputtering at room temperature. As a comparison, monolayer TaxOy coating was prepared on the surface of Ti6Al4V alloy. The morphology and phase composition of the coatings were investigated by field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD), the elemental chemical states of coating surfaces were investigated by X-ray photoelectron spectroscope (XPS). The adhesion strength and corrosion resistance of the coatings were examined by micro-scratch tester and electrochemical workstations, respectively. The results show that the adhesion strength of multilayer ZnO-TaxOy coating is 16.37 times higher than that of single-layer TaxOy coating. The ZnO-TaxOy composite coating has higher corrosion potential and lower corrosion current density than that of TaxOy coating, showing better corrosion inhibition. Furthermore, antibacterial test revealed that multilayer ZnO-TaxOy coating has a much better antibacterial performance by contrast. [ABSTRACT FROM AUTHOR]

• Ferrite coating layer can enhance SMCs' permeability, but lead to a relatively low DC-bias property. • C-SMCs exhibit lower P e of 20.2% of P cv as compared to that of 61.9% for R-SMCs coated alone with resin. • FeSi@SiO 2 &ferrite SMCs with fine magnetic properties faced shortcomings of long preparation time and high synthesis temperature. • SMC coated with inorganic material can be widely used in industry due to its friendly preparation conditions. The soft magnetic performances of the Fe-6.5 wt.%Si (FeSi) soft magnetic composites (SMCs) insulated with different materials, including organic, inorganic, and soft magnetic materials with high resistivity, and composite coating of inorganic-magnetic layer, under the same fabrication condition have been compared and analyzed by synchronously considering their coating preparation parameters. The core–shell structure of the coated powder was characterized by using a combination of SEM-EDS, FTIR, and XRD. Loss separation fitting model was established to evaluate the source of each part loss for the corresponding FeSi SMCs above. Due to the fact that the SMCs insulated with inorganic or/and magnetic ferrite materials exhibit high bulk resistivity more than 1.4 Ω·m, their eddy current losses account for lower contribution of only 20.2 ~ 22.1% of total core loss compared with that of 61.9% for the SMCs coated alone with organic resin. As compared to the other insulation materials, the SMCs coated using inorganic material (SiO 2 or TiO 2) exhibit a better DC-bias over 75.5%, higher retain real-part permeability exceed 44.6 at an applied field of 7960 A/m, a relatively low total core loss of 1040.6 kW/m3 at 100 kHz, 0.1 T, and can be fabricated at room temperature with a total preparation time of 70 min, which is favorable for being widely used in industry. The results of this work offered a referable ideal to design insulating layer for other SMCs. [ABSTRACT FROM AUTHOR]

• Poly-2-amiothiazole was successfully prepared to noncovalently modify the graphene (P-AT@rGO) via the in-situ polymerization. • P-TA@rGO acts as a functional nanofiller and an enhanced curing agent in the epoxy composite coatings. • The epoxy/P-AT@rGO composite coatings exhibit outstanding anticorrosion performance. In this work, an insulated poly-2-amiothiazole was successfully prepared to noncovalently modify the graphene (P-AT@rGO) via an in-situ polymerization. The superior anticorrosive performance of epoxy composite coatings was well demonstrated. Results exhibit that the epoxy composite coatings with 2.5 wt.% P-AT@rGO still maintain 2. 81 × 108 Ω cm2 of the polarization resistance after 30-days immersed in a 5.0 wt.% NaCl solution. Significantly enhanced protective performance of the epoxy composited coatings is attributable to the low electrical conductivity and the good dispersion of P-AT@rGO, the richer crosslinking densities, and the improved hydrophobicity. [ABSTRACT FROM AUTHOR]

• ZIF-8 was used as a multifunctional gatekeeper for HMSN-BTA. • HMSN-BTA@ZIF-8 was well-dispersed in epoxy matrix. • HMSN-BTA@ZIF-8 notably improved anticorrosion performance for epoxy coating. • HMSN-BTA@ZIF-8/epoxy coatings exhibited excellent self-healing performance. Zeolitic imidazole framework-8 (ZIF-8) with porous structure, pH-response and facile synthesis characteristics, as a molecule delivery and stimulus-response nanomaterial, has been widely investigated over the past decades. Here, we report for the first time a new corrosion inhibitor-encapsulated nanocontainer (denoted as HMSN-BTA@ZIF-8), successfully synthesized using ZIF-8 as self-sacrificial template, pH-responsive gatekeeper and interfacial compatibility assistant for hollow mesoporous silica nanoparticle (HMSN). Corrosion inhibitors of benzotriazole (BTA) are encapsulated in the cavity and mesopores of HMSN. The results demonstrate that there are outstanding pH-triggered activities to both acidic and alkaline conditions for HMSN-BTA@ZIF-8. Rather than physically dispersing nanocontainers in the coating matrix, the synthesized HMSN-BTA@ZIF-8 can covalently interact with epoxy resin, resulting in superior compatibility and more uniform dispersion behavior of nanocontainers in the coatings. Interestingly, the epoxy composite coating with HMSN-BTA@ZIF-8 exhibits excellent corrosion protection and outstanding self-healing performances, which are well characterized by potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS), salt spray test and Scanning Kelvin Probe (SKP) technique. The outstanding anticorrosion and impressive self-healing properties are attributed to the good compatibility of HMSN-BTA@ZIF-8, the hydrophobicity of ZIF-8, higher crosslinking densities, and the controllable release of BTA in the epoxy composite coating. It is believed that this work is very helpful for extending the service life of various anticorrosion coatings. [ABSTRACT FROM AUTHOR]

• Epoxidized biomass eucommia gum (EEUG) was successfully synthesized by an interfacial reaction. • EEUG/epoxy composite coatings with 1 wt% showed an improvement in the tensile strength. • EEUG/epoxy composite coatings with 1 wt% exhibited the outstanding anticorrosion protection performance. The design and preparation of a long term effective anticorrosion coating in a large scale in the harsh environment is still an enormous challenge for the anticorrosion technology. Herein, Eucommia gum, a natural biomass rubber material, had been epoxidized by a novel and green method involved in an interfacial reaction using the water as a dispersant. Epoxidized biomass eucommia gum (EEUG) is utilized as a functional filler in the synthesis of epoxy composite coating. The epoxy groups in the EEUG can react with the hardener, not only resulting in the event dispersion of EEUG in the composite coating, but also leading to the formation of the much richer crosslinking densities. A substantial improvement in the corrosion protection and the tensile strength were obtained. For example, EEUG/epoxy composite coatings with 1 wt% EEUG still maintains excellent anticorrosion performance with the high polarization resistance (R f) values of 8.846 × 108 Ω cm2 after 30 days of immersion times in the harsh environment (3.5 wt% NaCl solution, pH = 7). The implication of the present study for utilization of the natural biomass rubber material to enhance the physical and mechanical properties of polymeric matrixes has been discussed, and a great anticorrosion coating is provided. [ABSTRACT FROM AUTHOR]