Showing papers on "Salt spray test published in 2021"

Graphene oxide–cerium oxide hybrids for enhancement of mechanical properties and corrosion resistance of epoxy coatings

Abstract: In this study, graphene oxide–cerium oxide (GO–CeO2) hybrids were synthesized through an in situ hydrothermal approach and were incorporated into epoxy resin to prepare a robust coating for aluminum alloy protection. The mechanical properties of the GO–CeO2-loaded coating were characterized by nano-indentation, friction-wear test and pull-off adhesion test, using pristine epoxy coating and GO-loaded epoxy coating for comparison. Results revealed that GO–CeO2 addition could increase the hardness, elastic modulus and the wear resistance and decrease the friction coefficient of the composite coating. Compared with pristine epoxy coating, the adhesion strength of GO–CeO2/epoxy coating increased from 7.3 MPa to 12.2 MPa. Such improvement in the mechanical properties can be explained by the good dispersion of GO–CeO2 in the composite coating. In addition, salt spray and electrochemical impedance spectroscopy (EIS) measurement results showed that the corrosion resistance of the GO–CeO2-loaded coating was significantly enhanced. After 30 days of salt spray test, the coating resistance of the GO–CeO2/epoxy coating was 17.8 and 3.5 times higher compared with that of the blank epoxy coating and GO/epoxy coating, respectively. The superior barrier performance of the composite coating was mainly ascribed to the synergistic effects of the prolonged pathway against corrosive media permeation and the corrosion inhibition effect of CeO2 particles.

Study on the Corrosion Resistance of Graphene Oxide-Based Epoxy Zinc-Rich Coatings.

Abstract: In order to improve the corrosion resistance of zinc-rich epoxy coatings and reduce the amount of zinc used, first, graphene oxide (GO) was modified by sulfonated multiwall carbon nanotubes (SMWCNTs) to obtain the modified graphene oxide (SM-GO). The samples were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and Raman spectroscopy. Then, four kinds of coatings were prepared, namely pure zinc-rich coating (0-ZRC), graphene oxide-based zinc-rich coating (GO-ZRC), sulfonated multiwall carbon nanotube-based zinc-rich coating (SM-ZRC) and SM-GO-based zinc-rich coating (SG-ZRC). The corrosion resistance of the above coatings was studied by open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), a salt spray test, 3D confocal microscope, and electron scanning electron microscope (SEM). The results indicate that GO is successfully non-covalently modified by SMWCNTs, of which the interlayer spacing increases and dispersion is improved. The order of the corrosion resistance is GO-ZRC > SG-ZRC > SM-ZRC > 0-ZRC. The addition of GO, SMWCNTs, and SM-GO increases the shielding effect and increases the electrical connection between Zn particles and metal substrates, which improves the corrosion resistance. However, SMWCNTs and SM-GO also strengthen the galvanic corrosion, which decreases the corrosion resistance to some extent.

Investigating the effects of g-C3N4/Graphene oxide nanohybrids on corrosion resistance of waterborne epoxy coatings

Abstract: Two dimensional nanomaterials including graphene oxide (GO), graphitic carbon nitride (CN), and their nanohybrids (GO@CN) are used for enhancing the corrosion resistance of waterborne epoxy coatings. The nanomaterials functionalized with 3-aminopropyltriethoxysilane are loaded in the waterborne epoxy matrix by solution mixing method through probe-sonication and mechanical mixing. The corrosion resistance of the pure waterborne epoxy (PE) and the nanocomposite coatings in 3.5 wt% NaCl solution is evaluated by electrochemical impedance spectroscopy and salt spray test; revealing that the epoxy coating loaded with 0.1 wt% silane functionalized GO@CN nanohybrid has the highest chemical stability and corrosion resistance, due to the well-distribution of the nanohybrid in the polymer matrix. This research exhibits the importance of developing nanocomposite coatings based on two dimensional nanohybrids to overcome the shortcomings of the nanomaterials and to simultaneously utilize from their advantages in a coating system.

Effect of TiB2 Particles on the Morphological, Mechanical and Corrosion Behaviour of Al7075 Metal Matrix Composite Produced Using Stir Casting Process

Abstract: Aluminium metal matrix composites are lightweight high-performance materials mostly applicable in aerospace, automobile and marine applications. In this study, the morphological, mechanical and corrosion behaviour of Al7075 metal matrix composites were investigated to find the effect of reinforcement of TiB2 particles for various weight percentage. Al7075-TiB2 composites were developed by reinforcing the 3–5 µm size TiB2 ceramic particles using stir casting process. The particles with different weight percentage of 2, 4, 6 and 8 were uniformly reinforced with the help of the mechanical stirrer. The energy dispersive X-ray diffraction (EDAX) pattern confirms the presence of TiB2 particles in the composites. SEM and optical microstructures clearly revealed the uniform distribution of TiB2 particles in the aluminium matrix. The additions of TiB2 particles enhance the tensile strength and micro hardness due to the strong interface and load sharing between the matrix and the reinforcement particles. Dry sliding wear test was conducted by varying the applied load and sliding distance. SEM microstructure of worn surfaces shows that addition of TiB2 particles decreases the wear rate due to the presence of stiffer and stronger reinforcement particles. The electrochemical potentiodynamic polarization and salt spray test were also conducted to study the corrosion behaviour of the Al-TiB2 composites. SEM microstructures confirm the occurrence of pitting corrosion and shows that addition of TiB2 particles improves the corrosion resistance.

Superhydrophobic Coatings with Photothermal Self-Healing Chemical Composition and Microstructure for Efficient Corrosion Protection of Magnesium Alloy.

Abstract: Self-healing superhydrophobic coatings have a wide potential for practical applications by prolonging their lifespan, but still suffer from some shortcomings, for example, difficulty in repairing microstructure damage, limited self-healing cycles, and more importantly the inability to self-heal while in service. Herein, we present the fabrication of superhydrophobic coatings having photothermal self-healing chemical composition and microstructure for the high performance anticorrosion of Mg alloy. The coatings contain a shape-memory polymer (SMP) primer and an upper superhydrophobic coating composed of fluorinated polysiloxane-modified multiwalled carbon nanotubes (PF-POS@MWCNTs). The coatings have good superhydrophobicity, photothermal effect, and anticorrosion performance. The coatings show excellent self-healing performance in response to chemical and microstructure damage, such as rapid self-healing under 1 sun irradiation in 10 min, complete self-healing after serious damage (e.g., 10 damage and self-healing cycles and complex microstructure damage), and even self-healing under natural sunlight in 4 h. Moreover, the self-healed coatings show good corrosion protection for magnesium alloy in the neutral salt spray test. These are because of the combination of the SMP primer with good shape-memory effect and the PF-POS@MWCNTs coating with good superhydrophobicity, photothermal effect, and embedded PF-POS. The coatings are self-healable under natural sunlight while in service and thus may find applications in diverse fields.

A study on corrosion behavior of micro-arc oxidation coatings doped with 2-aminobenzimidazole loaded halloysite nanotubes on AZ31 magnesium alloys

Abstract: Micro-Arc oxidation (MAO) coatings with actively protective functionality by incorporating 2-aminobenzimidazole (2-ABi) loaded halloysite nanotubes (HNTs) was presented. The coatings were characterized by SEM, EDX and XRD. Corrosion behavior was evaluated by EIS, PDP and salt spray test. With the SEM and EDX analysis, the existence of HNT or 2ABi-loaded HNT was confirmed. The OCP evolution, EIS complex spectra and the result of salt spray test showed the enhanced corrosion resistance of 2-ABi-HNT MAO coating owing to the self-healing effect, suggesting 2-ABi has good potential as corrosion inhibitor for Mg alloys.

Effect of manganese addition on the appearance, morphology, and corrosion resistance of hot-dip galvanized zinc coating

Abstract: The study investigates the effect of manganese addition in the hot-dip galvanized zinc coating on steel. The Zn Mn hot-dip coatings were prepared under ambient conditions on a steel sheet using a custom-made galvanization simulator. The Zn Mn 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.

APTES Modification of Molybdenum Disulfide to Improve the Corrosion Resistance of Waterborne Epoxy Coating

Abstract: MoS2 has been regarded as a promising addition for the preparation of epoxy-based coatings with high anticorrosion ability. However, its dispersion and compatibility remain significant challenges. In the present work, an organic thin layer was well coated on lamellar molybdenum disulfide (MoS2) via a simple modification of 3-aminopropyltriethoxysilane (APTES). The modification of hydrolyzing APTES on lamellar MoS2 effectively improved the dispersity of MoS2 in water-borne epoxy (WEP) and successfully enhanced the compatibility and crosslinking density of MoS2 with WEP. The influence of introducing MoS2-APTES into WEP coating on anticorrosion property for N80 steel was tested by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and salt spray test. The results exhibited that the |Z|0.01Hz value of MoS2-APTES/WEP still reached 3.647 × 107 Ω·cm2 even after the immersion time of 50 days in 3.5 wt.% NaCl solution, showing an extraordinary performance of corrosion resistance. The enhanced anticorrosion performance of composite coating could be resulted from the apparently increased dispersibility and compatibility of MoS2 in WEP.

Mechanical clinching and self-pierce riveting for sheet combination of 780-MPa high-strength steel and aluminium alloy A5052 sheets and durability on salt spray test of joints

Abstract: 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.

Improved performance of Ti-based conversion coating in the presence of Ce/Co ions: Surface characterization, electrochemical and adhesion study

Abstract: Novel chromium-free conversion coatings based on titanium-cerium (Ti/Ce-CC) and titanium-cobalt (Ti/Co-CC) were prepared to enhance the anti-corrosion resistance and adhesion property of the organic coating applied on Al-2024 substrate. The surface characteristics of the modified titanium conversion coating (Ti-CC) were evaluated by field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), Tungsten microelectrode and contact angle measuring device. The electrochemical behavior of conversion coatings was evaluated by electrochemical impedance spectroscopy (EIS) measurement. Anti-corrosion and adhesion properties of polyurethane coating were evaluated by EIS, salt spray test and pull-off measurement. FE-SEM and AFM results show that by the addition of cerium and cobalt ions, the morphology of Ti-CC was completely changed. Oxide and hydroxide form of the different valence of cerium and cobalt ions were existed on the surface based on XPS spectra. The maximum surface energy is obtained for Ti/Ce-CC. Electrochemical data revealed that the Ti/Ce-CC enhance the anti-corrosion resistance to a significant degree (271.11 × 103 Ω.cm2) compare to the bare sample (3.70 × 103 Ω.cm2). The polyurethane coating applied on Ti/Ce-CC showed minimum delamination, highest anti-corrosion resistance and better adhesion strength in comparison with the Ti/Co-CC, Ti-CC and bare coated samples.

Microstructure and corrosion resistance of TiN/TiO2 nano-composite film on AZ31 magnesium alloy

Abstract: The high corrosion rate of Mg alloy restricts its application. In this paper, a nano-composite film as TiN/TiO2 was introduced to Mg alloy to improve the corrosion resistance. The nano-composited film was fabricated by atomic layer deposition (ALD) and in-situ oxidation (20 SCCM oxygen flow, at 250 °C, duration ≥ 20 min). When oxygen is introduced, the initial ALD-ed crystalline TiN layer is rapidly oxidized till the amorphous TiO2 layer is saturated. A stable TiN/TiO2 nano-composited film would be obtained then. X-ray photoelectron spectroscopy depth (XPS-depth) and transmission electron microscopy image (TEM) show that the nano-composite film has an interlayer structure. The nano-composite film shows good adhesion to the Mg alloy substrate in the nano-indentation analysis. Moreover, the nano-indentation scratches heal to a certain degree after 48 h, which means the film could self-heal. With the film, the surface potential mapping is not only overall higher but also less fluctuating by scanning Kelvin probe (SKP) analysis. There is a higher Ecorr (increasing ~0.42 V) and a much lower icorr (decreasing ~1/200) for potentiodynamic polarization (PDP) measurement. Equivalent circuit fitting for electrochemical impedance spectroscopy (EIS) profile changes from Rs(CPE1Rct) to Rs(CPE2(Rf(CPE1Rct))). The film makes less corroded withing a more uniformed corroded mode during neutral salt spray test (NSS). All these indicate that Mg alloy corrosion resistance is greatly improved. The work not only provides a flexible method for the interlayer composite film fabrication but also make an effective surface modification for Mg alloy corrosion resistance.

Preparation and comparative study of anticorrosion nanocomposites of polyaniline/graphene oxide/clay coating

Abstract: In this study, novel anticorrosion coatings including doped polyaniline, reduced graphene oxide (RGO) and modified clay sodium montmorillonite (Na-MMT) were synthesized. The nanocomposite particles were coated on carbon steel after optimal mixing and dispersion in epoxy resin. In order to increase the dispersibility and increase the functional groups between the graphene plates, the initial graphene oxide nanoparticles were re-oxidized and finally reduced to have a better dispersibility in the composite environment. Sodium dodecyl benzene sulfonic acid (SDBS) was used as a secondary dopant and surfactant. Synthesized nanocomposites were characterized using Fourier-transform infrared spectroscopy (FTIR), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Furthermore, Open Circuit Potential (OCP), Electrochemical Impedance Spectroscopy (EIS), Fourier-transform infrared spectroscopy (FFT), and salt spray test were used to investigate the electrochemical and anticorrosion behavior of the synthesized composite. The results showed that the initiative of adding certain ratios of RGO and Na-MMT to the polyaniline polymer significantly increased the anticorrosion properties of the coating. It was also found that at the same part ratios, the anticorrosion property of RGO is higher than the anticorrosion property of Na-MMT. According to the Tafel test, the corrosion current of the synthesized nanocomposite was 0.065 μA cm−2, which was lower than the corrosion current of other samples and shows the superiority of the anticorrosion property of this sample. Also, after 720 h of Salt spray test (In 3.5% wt NaCl), a very high and desirable durability of this sample (Sample a) has been observed.

Effect of Magnesium on Corrosion Behavior of Hot-Dip Zn-Al-Mg Coating

Abstract: The present study aims at to study the effect of Mg variation on corrosion behavior of Zn-5Al-xMg (where x = 1.5 and 4.5 wt.%) hot-dip coating. The hot-dip Zn-5Al-xMg coating on steel substrate was carried out using Hot-dip process simulator (HDPS). Microstructure of the Zn-5Al-xMg coating was characterized using scanning electron microscope and x-ray diffraction. Micro-harness of the Zn-5Al-4.5Mg coating has been found to be ~ 3 times higher than that of galvanized coating. The corrosion behavior of the coatings was studied using dynamic polarization and electrochemical impedance spectroscopy (EIS) techniques in 3.5% NaCl solution as well as salt spray test (SST) in 5% NaCl solution. Zn-5Al-4.5Mg coating has exhibited two times higher corrosion resistance as compared to that of Zn-5Al-1.5Mg coating and 10 times higher corrosion resistance than conventional galvanized coating. Mechanism of corrosion has been analysed and discussed. The spot weldability of Zn-5Al-xMg coated steels has been found to be comparable to that of conventional galvanized (GI) steel sheets.

Investigation of Mechanical Properties and Salt Spray Corrosion Test Parameters Optimization for AA8079 with Reinforcement of TiN + ZrO2

Abstract: This work mainly focuses on increasing the mechanical strength and improving the corrosion resistance of an aluminum alloy hybrid matrix. The composites are prepared by the stir casting procedure. For this work, aluminum alloy 8079 is considered as a base material and titanium nitride and zirconium dioxide are utilized as reinforcement particles. Mechanical tests, such as the ultimate tensile strength, wear, salt spray corrosion test and microhardness test, are conducted effectively in the fabricated AA8079/TiN + ZrO2 composites. L9 OA statistical analysis is executed to optimize the process parameters of the mechanical and corrosion tests. ANOVA analysis defines the contribution and influence of each parameter. In the tensile and wear test, parameters are chosen as % of reinforcement (3%, 6% and 9%), stirring speed (500, 550 and 600 rpm) and stirring time (20, 25 and 30 min). Similarly, in the salt spray test and microhardness test, the selected parameters are: percentage of reinforcement (3%, 6% and 9%), pH value (3, 6 and 9), and hang time (24, 48 and 72 h). The percentage of reinforcement highly influenced the wear and microhardness test, while the stirring time parameter extremely influenced the ultimate tensile strength. From the corrosion test, the hang time influences the corrosion rate. The SEM analysis highly reveals the bonding of each reinforcement particle to the base material.