Nowadays, the exploration of electromagnetic (EM) wave absorbers with anticorrosion to improve the survivability and environmental adaptability of military targets in the harsh environments is ...becoming an attractive and unavoidable challenge. Herein, through modulation of the metal composition in the precursors, the core@shell structure Prussian blue analog‐derived NiCo@C, CoFe@C, NiFe@C, and NiCoFe@C are obtained with excellent EM wave absorption performance. As for NiCoFe@C, ascribed to the coupling effect of the dual magnetic alloy, a minimum reflection loss (RL) of −47.6 dB and an effective absorption bandwidthof 5.83 GHz are realized, which cover the whole Ku‐band. Meanwhile, four absorbers display the lower corrosion current density (10−4–10−6 A cm−2) and larger polarization resistance (104–106 Ω) under acid, neutral, and alkaline corrosion conditions over uninterrupted 30 days. Furthermore, due to the spatial barrier effect and the passivation effect of the graphitic carbon shell , the continuous salt spray test has little effect on RL performance and inconspicuously changes the surface morphologies of coating, demonstrating its excellent bifunctional performance. This work lays the foundation for the development of metal–organic frameworks‐derived materials with both anticorrosion and EM wave absorption performance.
A series of bifunctional prussian blue derivatives are prepared by component engineering and displayed an −47.6dB reflection loss and an effective absorption bandwidth of 5.83 GHz, as well as the anticorrosion ability due to the shell protection effect. This work provides rational design for fabricating other metal–organic framework based electromagnetic wave absorbers for the practical applications
The study investigates the effect of manganese addition in the hot-dip galvanized zinc coating on steel. The ZnMn hot-dip coatings were prepared under ambient conditions on a steel sheet using a ...custom-made galvanization simulator. The ZnMn hot-dip coatings were always covered with oxides formed during the withdrawal, giving patchy coloration. A novel approach is demonstrated to prevent patchy coloration due to these oxides and produce alloy coated surfaces with homogeneous coloration. The microstructures of the alloy coated sheets were investigated to identify the effect of the Mn addition. The microstructure changes in the alloy coating due to increasing Mn addition were correlated to the composition, hardness of the individual intermetallic layers, and the basal texture. Compared to the hot-dip Zn coating, Mn addition decreased the corrosion rate (icorr from potentiodynamic polarization test) in the alloy coating by 65%. The Mn addition also controlled the degree of the white rust formation and prolonged the life of the alloy coated steels in accelerated salt spray test (> 300 h of exposure, ASTM B117). The bend test results show that Mn addition does not affect the deformation tolerance of the hot-dip alloy coatings.
•Novel technique to achieve colorless ZnMn alloy coatings by hot-dip galvanization.•Manganese addition increased the TC of the basal plane and increased coating life.•Hot-dip galvanized alloy coating with Mn does not affect the formability of the metal.•Mn addition also controls patina formation in hot-dip galvanized ZnMn coating
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•Lysine was used to modify graphene oxide (LY-GO).•LY-GO is better compatible with water-borne epoxy (EP) than GO.•The anti-corrosion properties of LY-GO/EP are significantly ...improved.
To develop the compatibility of graphene oxide (GO) nanosheets with water-borne epoxy (EP) coatings, a natural amino acid with double amines (Lysine) was used to modify GO (LY-GO). Results obtained from Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) confirm that Lysine is successfully decorated on GO surface by formation of chemical bonds. Then LY-GO nanomaterials were introduced into EP coatings on the mild steel substrate. The SEM images demonstrate that distribution of LY-GO in EP coatings was remarkably improved due to Lysine modification. The effect of LY-GO and GO nanosheets on the anti-corrosion property of the EP coating was studied by potentiodynamic polarization test, electrochemical impedance spectroscopy (EIS), and salt spray test. Results reveal that well-distributed LY-GO nanosheets remarkably reinforce the anti-corrosion performance of the EP coatings. At the same filler content, LY-GO provides EP coating with better anti-corrosion property of than GO and the corrosion rate of LY-GO/EP coating is approximately two orders of magnitude lower than that of GO/EP. Moreover, LY-GO can also effectively decrease the coating delamination degree during salt spray test of 500 h.
Aiming to enhance the weathering resistance of UV curable coatings, this study prepared a series of UV-curable composite coatings using TiO2 particles as filler and systematically evaluated the ...influences of TiO2 on the UV-curing process and weathering performance. The effect of TiO2 on the curing process of the UV-cured coating was assessed by double bond conversion rate, gel content test and curing depth. The weathering resistance of the UV-cured coating was evaluated by color and gloss change, FTIR spectroscopy, SEM images as well as anticorrosion property through artificial accelerated UV aging test. The results showed that the presence of TiO2 has a negative effect on the curing efficiency, but by properly tuning the TiO2 content and coating thickness, a fully UV-cured coating with high double bond conversion and gel content could still be prepared. During accelerated UV aging test, the UV-cured TiO2 composite coating exhibited a much smaller change in color, gloss, morphology, and surface chemistry than pristine coatings, demonstrating the presence of TiO2 could remarkably enhance the weathering resistance of UV curable coatings. Salt spray test shows better anti-corrosion behavior of the aged composite coating compared to aged pure resin coating.
•UV-curable coatings with outstanding weather resistance were prepared using TiO2 particles as fillers.•A fully UV-cured coating could be prepared by properly tuning the coating thickness and TiO2 content.•TiO2 can significantly improve the weather resistance of the UV-cured coating.•Compared with aged pure resin coating, the aged composite coating has better anti-corrosion behavior.
•Homogeneous distribution of 8-hydroxyquinoline loaded nanocontainers in polyester powder coatings.•Controlled release of encapsulated 8-hydroxyquinoline at different pH.•Increased corrosion ...protection of nanocontainer-impregnated coatings over 1000h of salt spray test.•Loading of free inhibitor in the coating leads to the coating deterioration even after 260h of salt spray test.
We carried out comparative study of the effect of inhibitor-loaded nanocontainers on corrosion protection performance of polyepoxy powder coatings employing neutral salt-spray test (5% NaCl, 35°C, different time). We demonstrated that halloysites and mesoporous silica particles loaded with corrosion inhibitor 8-hydroxyquinoline can be homogeneously distributed in powder coating effectively reducing corrosion of the metal substrate over 1000h of salt-spray test. Addition of only 2wt.% of inhibitor encapsulated in both nanocontainers to the powder coating is sufficient to decrease the delamination effect by 2–3 times and suppress the formation of the pitting corrosion.
Corrosion testing of anodized aerospace alloys is often performed by immersion and salt spray tests, according to specific international standards. The two tests differ not only in the physical ...exposure conditions but also in the standard testing temperature. In this work, the individual effects of temperature and exposure type on the protective performance of different anodic oxides are considered. It is found that the testing temperature has a significant effect on the overall corrosion behavior of the anodized alloy during the immersion test, but it has a reduced effect during the salt spray test.
•The effect of temperature on the corrosion test of anodized AA2024T3 was investigated.•The temperature has a significant effect on corrosion behavior during immersion testing.•The temperature has little influence on the corrosion behavior during salt spray testing.•The performance of different anodic oxides depends both on test type and on test temperature.
•The addition of Cu reduces the corrosion resistance of the A356 aluminum alloy.•The number and size of pores in A356 cast aluminum alloys increases with the increase in the content of the metal ...element Cu.•Corrosion of the alloy occurs mainly in the non-precipitated regions at the edges of the Al2Cu particles and Si particles.
In this article, the pore and precipitation phases of A356 aluminum alloy were regulated by adding element Cu, and the corrosion kinetic behavior was investigated by electrochemical experiments and salt spray test (SST), while the corrosion mechanism of A356 aluminum alloy was studied by scanning electron microscopy (SEM), 3D laser confocal microscopy (LSCM) and atomic force microscopy (SKPFM). The results of both electrochemical and salt spray experiments showed that the corrosion rate increased with increasing Cu content, and the average corrosion rate increased from 0.040 mm y-1 to 0.329 mm y-1 when the Cu content increased from 0 wt% to 7 wt%, and the Cu free alloy exhibited a greater charge transfer resistance. This is mainly due to the addition of Cu on the one hand to increase the number of precipitation phase, Al2Cu become the main precipitation phase, SKPFM test results show that the precipitation phase relative to the Al matrix potential difference in order: Al2Cu (350 ∼ 380 mV), Si (250 ∼ 275 mV), Mg2Si (80 ∼ 110 mV), the increase in potential difference between the two phases to promote the corrosion of occurrence. On the other hand, CT results showed that the average diameter of pores increased from 89.95 µm to 281.00 µm, and the volume fraction increased from 0.05 % to 0.18 %, and the larger and more porous pores help promote corrosion. Therefore, how to control the porosity and precipitation phase is an important factor in regulating the corrosion behavior of A356 aluminum alloy.
To increase the usage of high-strength steel and aluminium alloy sheets for lightweight automobile body panels, the joinability of sheet combinations including a 780-MPa high-strength steel and an ...aluminium alloy A5052 sheets by mechanical clinching and self-pierce riveting was investigated for different tool shapes in an experiment. All the sheet combinations except for the two steel sheets by self-pierce riveting, i.e., the two steel sheets, the two aluminium alloy sheets, and the steel-aluminium alloy sheets, were successfully joined by both the joining methods without the gaps among the rivet and the sheets. Then, to show the durability of the joined sheets, the corrosion behaviour and the joint strength of the aged sheets by a salt spray test were measured. The corrosion and the load reduction of the clinched and the riveted two aluminium alloy sheets were little. The corrosion of the clinched two steel sheets without the galvanized layer progressed, and then the load after 1176 h decreased by 85%. In the clinched two galvanized steel sheets, the corrosion progress slowed down by 24%. In the clinched steel and aluminium alloy sheets, the thickness reduction occurred near the minimum thickness of the upper sheet and in the upper surface on the edge of the lower aluminium alloy sheet, whereas the top surface of the upper sheet and the upper surface of the lower sheet were mainly corroded in the riveted joint. The load reduction was caused by the two thickness reductions, i.e., the reduction in the minimum thickness of the upper sheet and the reduction in the flange of the aluminium alloy sheet. Although the load of the clinched steel without the galvanized coating layer and aluminium alloy sheets decreased by about 20%, the use of the galvanized steel sheet brought the decrease by about 11%. It was found that the use of the galvanized steel sheets is effective for the decrease of strength reduction due to corrosion.
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•A thin, compact and few-cracking conversion coating was fabricated on EV31.•The self-healing property was performed due to addition of Ce in KMnO4 solution.•Ce / Mn coating reduced ...the corroded area to approximately 3% after 168 h SST.•The mechanism via self-healing of Ce / Mn conversion coating was proposed.
Magnesium alloys have been widely employed in the aerospace and aviation applications due to the unique properties. Nevertheless, Mg alloys were sensitive to corrosion attacks. The use of hexavalent chromium has been strictly banned because of severe toxicity and harm, even though it provided useful protective coating. Many efforts have been made to find the alternative process to hexavalent chromium conversion process.
In this study, the Ce / Mn conversion coating was developed on EV31 Mg alloy. A thin, homogeneous, and compact conversion coating layers was formed. The electrochemical impedance spectroscopy (EIS), potentiodynamic polarization tests and salt spray test (SST) were used to evaluate the corrosion resistance of the coatings accompanying with a cross-cut scratches. The total impedance of the Ce / Mn conversion coating rose to 2.3 × 103 Ω‧cm2 compared with 3.4 × 102 of the bare EV31. Furthermore, the Ce / Mn conversion coating passed the 168 h of SST with less than 3% corrosion area, and meanwhile the self-healing worked effectively. Both barrier protection and characteristic self-healing effect enhanced corrosion resistance on EV31. Furthermore, a corrosion mechanism for the coating in practice was proposed to discussion.
Abstract
In order to improve the service life of railway fasteners under various environmental conditions, the Zn and Zn-Mg coating were prepared on the railway fastener gaskets by powder ...impregnation. XRD and SEM were used to characterize the phase composition, microstructure and morphology before and after the salt spray. The neutral salt spray test (NSST) and the electrochemical workstation were used to characterize the corrosion resistance of the two coatings. Results show that there was a large area of red rust on Zn coating after 480 hours of NSST, while there was no red rust on Zn-Mg coating after 1920 hours of NSST. The impedance of the Zn-Mg coating reached 1015.6 Ω·cm
2
, about 3.65 times of the Zn coating. Zn-Mg coating’ current density was 3.27 μA·cm
−2
, which was only 21% of the Zn coating. MgZn
2
and Mg
2
Zn
11
phases were easier to formed in Zn-Mg coating due to the infiltration of magnesium, forming a dense and protective layer, thereby greatly improved its corrosion resistance.
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