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Corrosion performance of ZnO-Based hybrid coated mild steel in concrete pore solutions
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Epoxy resins were reinforced with different ZnO nanofillers (commercial ZnO nanoparticles (ZnO NPs), recycled ZnO and functionalized ZnO NPs) in order to obtain ZnO–epoxy composites with suitable mechanical properties, high adhesion strength, and good resistance to corrosion. The final properties of ZnO–epoxy composites depend on several factors, such as the type and contents of nanofillers, the epoxy resin type, curing agent, and preparation methods. This paper aims to review the preparation methods, mechanical and anti-corrosion performance, and applications of ZnO–epoxy composites. The epoxy–ZnO composites are demonstrated to be valuable materials for a wide range of applications, including the development of anti-corrosion and UV-protective coatings, for adhesives and the chemical industry, or for use in building materials or electronics.
The effects of S addition on the corrosion behaviors of Sn–9Zn solder alloy in the acidic and alkaline solutions were investigated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) techniques, and weight loss test. The results show that 0.02–0.08 wt% S can enhance the corrosion resistance of Sn–9Zn solder alloy in both solutions, evidenced by much lower corrosion current density, higher impedance modulus, lower corrosion rate, and less weight loss. When the content of S is around 0.08 wt%, the solder alloy exhibits the best corrosion resistance in both solutions. SEM and XRD results show that the corroded surface of the S-containing Sn–9Zn solder alloy is mainly covered with shorter grooves and a more uniform ZnSn(OH)6 layer than that of Sn–9Zn without S when being exposed to the alkaline solution, which is favorable to provide better protection for the underlying solder alloy and improve its corrosion resistance. After being immersed in the acidic solution, Sn–9Zn–0.08S solder alloy shows more obvious and uniform intergranular corrosion characteristics, with a few shorter grooves and cracks on the corrosion surface compared to that of Sn–9Zn. The corrosion products formed on the exposed surface of Sn–9Zn–xS solder alloy in acidic conditions are SnO2, SnO, and Zn5(OH)8Cl2·H2O. The corrosion characterizations of Sn–9Zn–xS in acid and alkaline solutions were fully discussed, and the possible mechanisms were proposed.
This study aims to enhance the practical performance of PVDF/ZnO and PVDF/TiO2 composite coatings known for their distinctive properties. The coatings, applied through spray coating with PVDF and ZnO or TiO2 nanoparticles on glass, steel, and aluminum substrates, underwent a comprehensive evaluation. Surface wetting properties and morphology were respectively evaluated using a technique involving liquid droplets and an imaging method using high-energy electrons. Potentiodynamic polarization was used to compare corrosion resistance between coated and bare substrates. Nanoindentation was used to assess coating hardness, and bonding strength was subsequently quantified. The results revealed that PVDF/ZnO composite coatings had higher water contact angles (161 ± 5° to 138 ± 2°) and lower contact angle hysteresis (7 ± 2° to 2 ± 1°) compared to PVDF/TiO2 and PVDF coatings. Moreover, corrosion tests demonstrated superior protection for steel and aluminum surfaces coated with superhydrophobic PVDF/ZnO. Nanoindentation indicated enhanced mechanical properties with TiO2 nanoparticles, with adhesion results favoring TiO2 over ZnO nanoparticles.
This research presents novel findings by exploring the synergistic effects of incorporating nano-sized titanium dioxide (TiO₂) and zinc oxide (ZnO) nanoparticles into a high-performance concrete (HPC) matrix. The study utilized Response Surface Methodology (RSM) to determine the optimal combinations of TiO₂ and ZnO for achieving peak performance within the matrix. Various combinations of TiO₂ and ZnO, ranging from 0 % to 2 %, were incorporated into HPC mixes, focusing on evaluating their effects on compressive strength (CS), splitting tensile strength (STS), flexural strength (FS), durability, and photocatalytic properties. The results revealed that maintaining higher proportions of TiO₂ over ZnO led to superior mechanical properties, with the most effective combination determined to be 2 % TiO₂ and 1.33 % ZnO, which agrees with the prediction by the RSM model and verified through experimental testing. However, these combinations did not significantly enhance the durability properties of the HPC samples when exposed to acidic curing for three months.On the other hand, the photocatalytic properties of HPCs with different combinations of TiO₂ and ZnO were significantly improved. The combination with the maximum content of both nanoparticles had only 23.7 % of Rhodamine B remaining on its surface after 100 hours of UV radiation. Comparing the individual effects of TiO₂ with ZnO, it was observed that a higher TiO₂ dosage (2 %) caused earlier Rhodamine B discolouration compared to a higher ZnO dosage (2 %). Therefore, based on the photocatalytic degradation efficiency, it was concluded that the concrete can confer self-cleaning properties under UV radiation and serve as a precursor for developing self-cleaning concrete composites for more sustainable and resilient structures.
Corrosion, which damages the rebar, is one of the main issues faced by reinforced concrete. In this study, a PVDF binder was combined with Zinc oxide and Nickel to increase the corrosion resistance of mild steel. The improved coating was tested using a simulated concrete pore solution. Changes in the characterization of the coating due to corrosion were evaluated using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) at the beginning and end of the process. The corrosion inhibition capacity was evaluated via open-circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and potential polarization experiments. The experimental findings demonstrate that the mild steel plate coated with a compound consisting of 0.75ZnO-0.25Ni/PVDF has exceptional corrosion resistance properties. The electrochemical tests were verified by an accelerated gravimetric test, which produced equivalent results and showed that the 0.75ZnO-0.25Ni/PVDF composites had an 87.47% corrosion inhibition capability. The electrochemical findings will serve as boundary conditions in COMSOL to model the coating and evaluate its effectiveness in a concrete rebar environment. The plots obtained from COMSOL include the electrolyte potential, electrolyte current density, and electrode potential. These results were compared for different samples, and the final result showed that the 0.75ZnO-0.25Ni/PVDF coating had the highest corrosion inhibition efficiency in a concrete rebar environment.
