Next Article in Journal
Design of 1D Photonic Crystals Sustaining Optical Surface Modes
Next Article in Special Issue
Investigation of the Microstructures and Properties of B-Bearing High-Speed Alloy Steel
Previous Article in Journal
MOF-Derived Hetero-Zn/Co Hollow Core-Shell TMOs as Anode for Lithium-Ion Batteries
Previous Article in Special Issue
Effect of the Testing Temperature on the Impact Property of a Multilayered Soft–Hard Copper–Brass Block
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Coatings
Volume 12
Issue 10
10.3390/coatings12101488
coatings-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Microstructure and Corrosion Resistance of Two-Dimensional TiO2/MoS2 Hydrophobic Coating on AZ31B Magnesium Alloy

by
Longjie Lai
1,2,
Heng Wu
1,3,
Guobing Mao
1,2,
Zhengdao Li
4,*,
Li Zhang
5 and
Qi Liu
1,2,*
1
School of Materials Science and Engineering, Anhui Polytechnic University, Wuhu 241000, China
2
Anhui Key Laboratory of High-Performance Non-ferrous Metal Materials, Anhui Polytechnic University, Wuhu 241000, China
3
School of Mechanical Engineering, Anhui Institute of Information Technology, Wuhu 241100, China
4
Chemistry and Pharmaceutical Engineering College, Nanyang Normal University, Nanyang 473061, China
5
Faculty of Institute of Photoelectronics Thin Film Devices and Technique of Nankai University, Nankai University, Tianjin 300071, China
*
Authors to whom correspondence should be addressed.
Coatings 2022, 12(10), 1488; https://doi.org/10.3390/coatings12101488
Submission received: 23 August 2022 / Revised: 28 September 2022 / Accepted: 1 October 2022 / Published: 6 October 2022
(This article belongs to the Special Issue Advances of Ceramic and Alloy Coatings)
Browse Figures
Versions Notes

Abstract

:
The corrosion resistance of magnesium alloys can be effectively improved by surface treatment. In this study, a hydrophobic two-dimensional (2D) TiO2/MoS2 nanocomposite coating was fabricated on AZ31B magnesium alloy by an electrophoretic deposition method. The corrosion resistance of the coating was evaluated using potentiodynamic polarization and electrochemical impedance spectroscopy analyses. After being modified by a silane coupling agent (KH570), the TiO2/MoS2 coating changed from hydrophilic to hydrophobic, and the static water contact angle increased to 131.53°. The corrosion experiment results indicated that the hydrophobic 2D TiO2/MoS2 coating had excellent anticorrosion performance (corrosion potential: Ecorr = −0.85 VAg/AgCl, and corrosion current density: Icorr = 6.73 × 10−8 A·cm−2). TiO2/MoS2 films have promising applications in magnesium alloy corrosion protection.

1. Introduction

Magnesium alloys, widely used in the aerospace and automotive industries, have the advantages of high specific strength, low density, good manufacturability and recyclability, and abundant resources [1,2,3,4]. However, due to the relatively active chemical properties of magnesium, low standard electrode potential, and poor protection ability of natural oxide film, the corrosion resistance of magnesium alloys is poor [5,6,7], which limits their wider application. Therefore, improving the corrosion resistance of magnesium alloys can greatly expand their practical application. The commonly used methods to improve the corrosion resistance of magnesium alloys include chemical conversion coating [8], plasma electrolytic oxidation [9], laser surface melting [10], shot peening [11], cold spraying [12], etc. These methods can improve the corrosion resistance of magnesium alloys, but the process is complex, costly, energy-intensive, and poses various environmental issues. On the other hand, constructing a thin film on the surface of magnesium alloys by electrodeposition can effectively slow down the corrosion rate of materials and has the advantages of low cost, convenient operation, rapid film formation, and ease of control [13,14].
Two-dimensional materials have attracted more attention for their potential applications in optics, electrochemical energy storage, biosensing, and other fields due to their special physical properties [15,16,17,18,19,20]. The 2D materials are also used as coatings to form protective layers, which can act as physical barriers to prevent contact between the corrosive medium and the substrate and avoid corrosion [21,22]. Since graphene was discovered, it has been widely used in the field of corrosion resistance due to its good chemical stability, high strength, and low friction coefficient [23,24,25]. Single-layer defect-free graphene can prevent the permeation of molecules. However, defective graphene will accelerate galvanic corrosion [26,27]. In recent years, an increasing number of graphene-like 2D materials have been discovered, such as MoS2, TiO2, boron nitride, C3N4, and MXene [28,29,30,31,32]. TiO2 and MoS2 are two promising two-dimensional materials that have great development potential in the field of anticorrosion. TiO2 has good chemical and thermal stability. At the same time, due to the lack of interconnected pores in TiO2, the corrosion resistance of TiO2 is higher than that of other metal oxides [33,34,35,36,37]. For instance, Devikala et al. [38] showed that with the increase in TiO2 concentration the corrosion resistance efficiency of composites increased. Rostami et al. [39] demonstrated that the addition of TiO2 improved the corrosion resistance of the pure cobalt film. Shams Anwar et al. [40] indicated that the addition of TiO2 nanoparticles improved the corrosion resistance of Zn-Ni alloys. MoS2 has attracted extensive attention in the field of corrosion protection because of its special (S-Mo-S) three-atomic-layer structure and excellent chemical stability [41,42]. For example, Xia et al. [43] prepared SiO2 nanoparticles modified by MoS2 nanosheets, which showed robust corrosion resistance. Hu et al. [44] demonstrated that nano-MoS2 on a zinc phosphate coating effectively promoted the phosphating process, which improved the corrosion resistance of Q235 low-carbon steel. Chen et al. [45] loaded nano-MoS2 on the surface of graphene oxide flakes, which endowed the composite coating with excellent barrier properties and significantly improved the corrosion resistance of the coating.
In this work, we describe our recent progress in the synthesis of the hydrophobic nanocomposite coating, which is 2D TiO2/MoS2 modified by a silane coupling agent, KH570. This was synthesized to enhance the corrosion resistance of AZ31B magnesium alloy. Because 2D TiO2 and MoS2 have similar electronegativity, MoS2 was added to TiO2 dispersion to obtain an electrophoretic solution. Then, a TiO2/MoS2 thin film was prepared on the surface of the magnesium alloy by electrophoretic deposition. The prepared 2D TiO2/MoS2 thin film was modified by KH570. The as-prepared thin film has hydrophobic properties and excellent corrosion resistance, which satisfies the demands of society and has broad application prospects.

2. Materials and Methods

2.1. Materials

AZ31B magnesium alloy (thickness of 1 mm, composition: 2.5–3.5 wt % Al, 0.6–1.4 wt % Zn, 0.2–1.0 wt % Mn, 0.04 wt % Ca, 0.003 wt % Fe, 0.001 wt % Ni, 0.08 wt % Si, 0.01 wt % Cu) was purchased from Dongguan Hongdi Metal Materials Co., Ltd. (Dongguan, China). Silane coupling agent KH570 was purchased from Jinan Xingfeilong Chemical Co., Ltd. (Jinan, China).

2.2. Preparation of TiO2/MoS2 Films

The TiO2 colloid and MoS2 were synthesized according to previous studies [46,47]. We added 0.7 mL of 1.0 mg/mL MoS2 aqueous solution to 100 mL of 70% ethanol solution containing 1 mL of TiO2 colloid. The two magnesium alloy substrates were kept at a distance of 15–20 mm in 5 mL of electrophoresis solution and electrophoresed for 90 s at a constant voltage of 20 V. After electrophoresis, the excess precipitates on the surface were washed with deionized water, dried at room temperature for 48 h, and heated at 150 °C for 60 min to obtain TiO2/MoS2 coating.

2.3. Preparation of TiO2/MoS2 Films Modified by KH570

The prepared samples were immersed in a beaker containing silane coupling agent, KH570 solution, for 30 min. After repeated rinsing with anhydrous ethanol, the silane-modified TiO2/MoS2 surface layer was obtained. The resultant product was denoted as TiO2/MoS2-K.

2.4. Analysis of Zeta Potential

The zeta potential of TiO2 and MoS2 was determined by Nanometrics (Malvern Zetasizer Nano ZS90, malvernpanalytical). Figure 1 shows the zeta potential diagrams of TiO2 and MoS2 measured at 25 °C. The measured electronegativity results are shown in Table 1. On the basis of Figure 1 and Table 1, it is shown that TiO2 and MoS2 have similar electronegativity. Therefore, MoS2 was added to the TiO2 dispersion, and both were deposited on the anode during electrophoresis deposition.

2.5. Characteristics of Morphology, Chemical Composition, and Hydrophobic and Anticorrosion Properties

The surface morphology of the samples was observed using an S-4800 scanning electron microscope (SEM, S-4800, Japan Hitachi Corporation, Tokyo, Japan). The phase structure of the samples was characterized by a D-8 X-ray diffractometer (XRD, D8, Beijing Brook Technology Co., Ltd., Beijing, China). The X-ray photoelectron spectroscopy (XPS) analysis was performed using a Thermo ESCALAB 250XI. Fourier transform infrared spectroscopy (FTIR, IRPrestige-21, Shanghai Yixiang Instrument Co., Ltd., Shanghai, China) was carried out for TiO2/MoS2 and TiO2/MoS2-K. Measurement of the static water contact angle on the sample surface was performed using a contact angle measuring instrument (SDC-100S, Dongguan Shengding Precision Instrument Co., Ltd., Dongguan, China); 6 μL was set as the drip volume in the test, and multiple measurements were performed at different positions on the surface of each sample, with the average value of multiple measurements taken for analysis. Metal corrosion in the atmosphere was simulated by a salt spray corrosion test box (DF-YWX/Q-150, Nanjing Defu Test Equipment Co., Ltd., Nanjing, China); 5 wt % NaCl solution was prepared as the test solution. The experimental temperature was controlled at 35 ± 2 °C, and the pressure of the atomized salt solution was maintained in the range of 69~172 kPa. The sample size was 10 × 10 × 1 mm. An electrochemical workstation (CHI760E, Shanghai Chenhua, Shanghai, China) was used to test the corrosion polarization curve of the magnesium alloy samples. A 3.5% NaCl solution was used as the electrolyte, and a three-electrode system was adopted, in which AgCl was used as the reference electrode and Pt was used as the counter electrode, and the scanning speed was 5 mV/s. The determination of Ecorr is the abscissa corresponding to the intersection of the cathode zone and the anode zone, and Icoor is the intersection of the tangent of the cathode zone and the vertical line corresponding to Ecorr.

3. Results and Discussion

3.1. Morphology Analysis of TiO2/MoS2 Films

The surface morphology of the films deposited on the magnesium alloy substrate at different magnifications is presented in Figure 2. According to Figure 2a,b, a layer of a fog-like film composed of nanosheets is evenly spread on the surface of AZ31B. The bright white point is due to the tiny residual particles of titanate when it is exfoliated into TiO2. In Figure 2c,d, the cracks are clearly displayed, which are caused by the accumulation of large amounts of MoS2 in the substrate surface solution during electrophoretic deposition. Figure 2d shows the microscopic magnification of the relatively flat area. The nanosheets are stacked together to form large particles. The surface roughness was increased, and obvious cracks could be observed. As shown in Figure 2e, the surface layer completely and uniformly covers the surface of AZ31B, and there is no honeycomb connection between the nanosheets, which becomes very dense. The contact between the surface of AZ31B and air or corrosive substances is completely isolated, and a good protective barrier is formed [48,49]. Figure 2f shows that the coating becomes denser after KH570 modification.

3.2. Compositional Analysis of TiO2/MoS2 Films

Figure 3 shows the XRD patterns of the AZ31B substrate, TiO2 and MoS2 powder and TiO2/MoS2 film. The difference in peak position represents the difference in TiO2 layer spacing, which proves that TiO2 with random layer spacing is prepared [50,51]. The peaks of MoS2 powder correspond to the hexagonal MoS2 standard card (JCPDS No. 37-1492). Notably, after preparing TiO2/MoS2 film on the surface of the magnesium alloy, the peaks of TiO2 and MoS2 are not obvious due to the strong peak of the AZ31B substrate. Combined with the results of the energy spectrum analysis of the corrosion products of the samples, TiO2/MoS2 films were successfully prepared.

3.3. XPS of TiO2/MoS2 Coating

XPS measurements were conducted to characterize the surface compositions. As shown in Figure 4, TiO2 features two characteristic peaks at around 463.9 and 458.2 eV, corresponding to the Ti 2p1/2 and Ti 2p3/2 components, respectively. In Figure 4c, two peaks at 233.1 and 229.9 eV are assigned to Mo 3d3/2 and Mo d5/2, which suggests that the majority of Mo at the surface is Mo4+. Simultaneously, the peak at 227.1 eV belongs to the S 2s orbital of MoS2. The S 2p XPS spectrum shows that two peaks located at 163.9 and 162.9 eV correspond to S 2p1/2 and S 2p3/2, which is consistent with the −2 oxidation state of sulfur. This confirms the successful synthesis of TiO2/MoS2.

3.4. Hydrophilicity Test of TiO2/MoS2 Films

The wettability of the material surface also has an important influence on the corrosion resistance of the material. It is generally believed that the hydrophobic surface makes it more difficult for water molecules or chloride ions to penetrate the metal surface due to the isolation effect, thereby inhibiting the corrosion of the metal [52,53,54]. The contact angles (CA) of the magnesium alloy and the TiO2/MoS2 and TiO2/MoS2-K films are presented in Figure 5a. As shown in Figure 5a, the CA of the magnesium alloy is 36.08°, indicating that the surface of the AZ31B substrate without coatings is hydrophilic. When the TiO2/MoS2 surface layer was electrophoretically deposited on the surface of the AZ31B substrate, the CA increased to 65.43°. When the TiO2/MoS2 film was modified by KH570, the CA value was 131.53°. Another important observation is that the surface of the alloy changes from hydrophilic to hydrophobic. This is because the silane coupling agent KH570 is hydrolyzed into silanol in the solution, and the silanol is condensed with -OH on the TiO2/MoS2 film [55]. The hydrophilic functional group (-OH) of the TiO2/MoS2 coating was replaced by the organic functional group in silanol, and the reaction process is shown in Formulas (1)–(3). Figure 5b shows the FTIR spectra of TiO2/MoS2 and TiO2/MoS2-K. Two new peaks of TiO2/MoS2-K at about 1240 and 1280 cm−1 are attributed to stretching vibrations of C-O-C. Meanwhile, the absorption peak at 1710 cm−1 is assigned to the stretching vibration of C=O. The intensity of TiO2/MoS2-K is weaker than that of TiO2/MoS2 because the organic functional groups in silanol replace -OH on the surface of silane-modified TiO2/MoS2. These results indicate that the surface of the TiO2/MoS2 surface layer is modified by KH570, thereby enhancing the surface hydrophobicity of TiO2/MoS2 [56]. This effectively isolates the magnesium alloy from making contact with liquid, making it more difficult for water molecules or chloride ions to penetrate the metal surface and effectively enhancing the corrosion resistance of the magnesium alloy [57].
CH2=C(CH3)COO(CH2)3Si(OCH3)3 + 3H2O → CH2=C(CH3)COO(CH2)3Si(OH)3 + 3CH3OH
CH2=C(CH3)COO(CH2)3Si(OH)3 + HO-(TiO2)n → CH2=C(CH3)COO(CH2)3Si-O-(TiO2)n + H2O + 2OH−
CH2=C(CH3)COO(CH2)3Si(OH)3 + HO-(MoS2)n → CH2=C(CH3)COO(CH2)3Si-O-(MoS2)n + H2O + 2OH−

3.5. Electrochemical Test of TiO2/MoS2 Films

Figure 6 shows the potentiodynamic polarization curves of all the samples in 3.5 wt % NaCl aqueous solution. The results of the test are summarized in Table 2. On the basis of Figure 6 and Table 2, it is shown that the corrosion current density (Icorr) of the magnesium alloy decreases after electrophoresis. The polarization curve shape of the sample after deposition is similar to that of the magnesium alloy substrate, indicating that the 2D films do not change the corrosion kinetics process of the magnesium alloy. The contact between the substrate and the corrosion medium is isolated by the surface thin film, which improves the corrosion resistance of the magnesium alloy to a certain extent. The corrosion potential (Ecorr) of the AZ31B magnesium alloy is −1.47 V and the Icorr is 6.81 × 10−4 A·cm−2, indicating that the corrosion resistance of the magnesium alloy matrix is poor [58]. The results show that the Ecorr of TiO2/MoS2-K has a higher potential compared with TiO2, MoS2, and TiO2/MoS2 composite coatings. Among them, TiO2/MoS2-K has the lowest Icorr. The Icorr values for the TiO2 and MoS2 surface layer are 5.13 × 10−6 and 2.19 × 10−5 A·cm−2, respectively, whereas that of the TiO2/MoS2 film is 3.69 × 10−7 A·cm−2. The Icorr of the TiO2/MoS2 film decreases by two orders of magnitude compared to the MoS2 film, which is due to the dense state of the TiO2/MoS2 coating. The Ecorr of the TiO2/MoS2-K film is −0.85 V, and the Icorr is 6.73 × 10−8 A·cm−2. Compared with the TiO2/MoS2 film, the Ecorr of the TiO2/MoS2-K film shifted positively by 0.15 V, and the Icorr decreased by six times. This indicates that the KH570 modification improved the corrosion resistance of the TiO2/MoS2 protective layer, which is ascribed to its effectively isolating the magnesium alloy from contacting the corrosive liquid.
To further characterize corrosion resistance, we used EIS to analyze the anticorrosion of the sample. Figure 7 shows the electrochemical impedance spectroscopy of magnesium alloy, TiO2, TiO2/MoS2-K. The electrochemical impedance spectroscopy data are described in detail by the numerical fitting of experimental data. The corresponding equivalent circuit was selected to fit the impedance data, as shown in Figure 8. The fitting circuit of the magnesium alloy substrate is shown in Figure 8a, and the fitting circuit of the samples with TiO2 film and those with TiO2/MoS2-K films is shown in Figure 8b [59]. The results are shown in Table 3. The circuit involves the solution resistance (Rs), the charge transfer resistance (Rct) of the Mg particles, and the electric double-layer capacitance (CPEdl) at the interface between the electrolyte and magnesium particles. Rp is the inductance resistance, and CPLfilm is the inductance, corresponding to the electrode reaction between the film layer and the electrolyte interface. It is reported that Rct is closely related to the corrosion process, that is, the higher the Rct, the better the corrosion resistance. It can be seen from the results that the impedance radius of the TiO2/MoS2-K sample is the largest, and the Rct value is the largest at 871.9 Ω·cm2, which is significantly higher than that of the magnesium alloy sample and the sample with the TiO2 film. It shows that the corrosion resistance of TiO2/MoS2-K is the highest, which is consistent with the results of the polarization curve.

3.6. Salt Spray Corrosion Experiment of TiO2/MoS2 Films

Figure 9 shows the comparison of the surface morphology of the magnesium alloy samples, electrophoretically deposited TiO2, and TiO2/MoS2-K after the neutral salt spray test for 24, 48, and 72 h. Table 4 shows the results of the energy spectrum analysis of the corrosion products of the samples. It can be seen from the data in Table 4 that, in addition to the original elements, Na and Cl elements were also added to all the corrosion products of the samples, indicating that the chemical corrosion process occurred in the samples and salt spray. Combined with the SEM images, it can be seen that pitting corrosion occurred on the samples with TiO2/MoS2-K film, which is similar to that on the samples with TiO2 coating. With increasing time, the corrosion area increased gradually, but it was smaller than that on the surface of the magnesium alloy and the samples with the TiO2 layer. This was mainly due to the good chemical stability of TiO2 and MoS2 and the formation of the dense protective layer after electrophoresis. The hydrophobic thin film modified by KH570 further delayed the corrosion of the magnesium alloy.
Figure 10 shows the salt spray corrosion weight gain of the magnesium alloy samples after electrophoretic deposition of TiO2 and TiO2/MoS2-K films. The weight gain rate of the sample with TiO2/MoS2-K is higher at the beginning of the test than that of the magnesium alloy sample and the sample with TiO2 coating. With increasing salt spray corrosion time, the weight gain rate of the sample gradually slows down because the corrosion products on the surface of the sample increase, which hinders the continuous reaction of chloride ion contact with the magnesium alloy surface. In addition, the weight gain of the sample with the TiO2/MoS2-K film is significantly lower than that of the former two samples, and the corrosion rate is the lowest. This result indicates that the TiO2/MoS2-K protective layer delayed the corrosion of the magnesium alloy to a greater extent and had the best corrosion resistance.

4. Conclusions

The TiO2/MoS2 coating was successfully prepared on the surface of the magnesium alloy by adding MoS2 in the electrophoretic deposition of TiO2. After the TiO2/MoS2 layer was modified by the silane coupling agent KH570, the wettability of the magnesium alloy surface was changed from hydrophilic to hydrophobic. The as-prepared TiO2/MoS2-K film had a contact angle of 131.53°. Combined with the electrochemical test and salt spray corrosion analysis, it can be seen that the TiO2/MoS2-K film developed a significantly improved anticorrosion property compared to the magnesium alloy. In addition, we anticipate a promising potential to transfer this technology to other metal substrates for important applications.

Author Contributions

Conceptualization, Q.L. and Z.L.; methodology, H.W.; investigation, L.L.; writing-original draft preparation, L.L.; writing-review and editing, G.M.; supervision, Q.L.; project administration, L.Z.; funding acquisition, Q.L. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the Natural Science Foundation of Anhui Province (No. 2008085ME132) and the Key Project of Anhui Provincial Department of Education (No. KJ2019A0157).

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Luo, K.; Zhang, L.; Wu, G.; Liu, W.; Ding, W. Effect of Y and Gd content on the microstructure and mechanical properties of Mg–Y–RE alloys. J. Magnes. Alloy. 2019, 7, 345–354. [Google Scholar] [CrossRef]
  2. Yang, Y.; Xiong, X.; Chen, J.; Peng, X.; Chen, D.; Pan, F. Research advances in magnesium and magnesium alloys worldwide in 2020. J. Magnes. Alloy. 2021, 9, 705–747. [Google Scholar] [CrossRef]
  3. Liu, H.; Tong, Z.; Yang, Y.; Zhou, W.; Chen, J.; Pan, X.; Ren, X. Preparation of phosphate conversion coating on laser surface textured surface to improve corrosion performance of magnesium alloy. J. Alloys Compd. 2021, 865, 158701. [Google Scholar] [CrossRef]
  4. Xianhua, C.; Yuxiao, G.; Fusheng, P. Research Progress in Magnesium Alloys as Functional Materials. Rare Met. Mater. Eng. 2016, 45, 2269–2274. [Google Scholar] [CrossRef] [Green Version]
  5. Song, J.; She, J.; Chen, D.; Pan, F. Latest research advances on magnesium and magnesium alloys worldwide. J. Magnes. Alloy. 2020, 8, 1–41. [Google Scholar] [CrossRef]
  6. Siddique, S.; Bernussi, A.A.; Husain, S.W.; Yasir, M. Enhancing structural integrity, corrosion resistance and wear properties of Mg alloy by heat treated cold sprayed Al coating. Surf. Coat. Technol. 2020, 394, 125882. [Google Scholar] [CrossRef]
  7. Yeganeh, M.; Mohammadi, N. Superhydrophobic surface of Mg alloys: A review. J. Magnes. Alloy. 2018, 6, 59–70. [Google Scholar] [CrossRef]
  8. Chang, S.-H.; Niu, L.; Su, Y.; Wang, W.; Tong, X.; Li, G. Effect of the pretreatment of silicone penetrant on the performance of the chromium-free chemfilm coated on AZ91D magnesium alloys. Mater. Chem. Phys. 2016, 171, 312–317. [Google Scholar] [CrossRef]
  9. Ballam, L.R.; Arab, H.; Bestetti, M.; Franz, S.; Masi, G.; Sola, R.; Donati, L.; Martini, C. Improving the Corrosion Resistance of Wrought ZM21 Magnesium Alloys by Plasma Electrolytic Oxidation and Powder Coating. Materials 2021, 14, 2268. [Google Scholar] [CrossRef]
  10. Liu, C.; Liang, J.; Zhou, J.; Wang, L.; Li, Q. Effect of laser surface melting on microstructure and corrosion characteristics of AM60B magnesium alloy. Appl. Surf. Sci. 2015, 343, 133–140. [Google Scholar] [CrossRef]
  11. Lu, F.-F.; Ma, K.; Li, C.-X.; Yasir, M.; Luo, X.-T.; Li, C.-J. Enhanced corrosion resistance of cold-sprayed and shot-peened aluminum coatings on LA43M magnesium alloy. Surf. Coat. Technol. 2020, 394, 125865. [Google Scholar] [CrossRef]
  12. Yao, H.-L.; Yi, Z.-H.; Yao, C.; Zhang, M.-X.; Wang, H.-T.; Li, S.-B.; Bai, X.-B.; Chen, Q.-Y.; Ji, G.-C. Improved corrosion resistance of AZ91D magnesium alloy coated by novel cold-sprayed Zn-HA/Zn double-layer coatings. Ceram. Int. 2020, 46, 7687–7693. [Google Scholar] [CrossRef]
  13. Hosseini, M.R.; Ahangari, M.; Johar, M.H.; Allahkaram, S.R. Optimization of nano HA-SiC coating on AISI 316L medical grade stainless steel via electrophoretic deposition. Mater. Lett. 2021, 285, 129097. [Google Scholar] [CrossRef]
  14. Guan, S.; Hao, L.; Yoshida, H.; Itoi, T.; Cheng, Y.; Seki, S.; Nishina, Y.; Lu, Y. Enhanced photocatalytic activity and stability of TiO2/graphene oxide composites coatings by electrophoresis deposition. Mater. Lett. 2021, 286, 129258. [Google Scholar] [CrossRef]
  15. Sun, T.-Y.; Hao, Y.; Wu, Y.-H.; Zhao, W.-J.; Huang, L.-F. Corrosion Resistance of Ultrathin Two-Dimensional Coatings: First-Principles Calculations towards In-Depth Mechanism Understanding and Precise Material Design. Metals 2021, 11, 2011. [Google Scholar] [CrossRef]
  16. Mak, K.F.; Shan, J. Photonics and optoelectronics of 2D semiconductor transition metal dichalcogenides. Nat. Photonics 2016, 10, 216–226. [Google Scholar] [CrossRef]
  17. Lu, Q.; Yu, Y.; Ma, Q.; Chen, B.; Zhang, H. 2D Transition-Metal-Dichalcogenide-Nanosheet-Based Composites for Photocatalytic and Electrocatalytic Hydrogen Evolution Reactions. Adv. Mater. 2016, 28, 1917–1933. [Google Scholar] [CrossRef] [PubMed]
  18. Kumar, K.S.; Choudhary, N.; Jung, Y.; Thomas, J. Recent Advances in Two-Dimensional Nanomaterials for Supercapacitor Electrode Applications. ACS Energy Lett. 2018, 3, 482–495. [Google Scholar] [CrossRef]
  19. Choi, W.; Choudhary, N.; Han, G.H.; Park, J.; Akinwande, D.; Lee, Y.H. Recent development of two-dimensional transition metal dichalcogenides and their applications. Mater. Today 2017, 20, 116–130. [Google Scholar] [CrossRef]
  20. Bhandavat, R.; David, L.; Singh, G. Synthesis of Surface-Functionalized WS2 Nanosheets and Performance as Li-Ion Battery Anodes. J. Phys. Chem. Lett. 2012, 3, 1523–1530. [Google Scholar] [CrossRef]
  21. Ding, R.; Chen, S.; Lv, J.; Zhang, W.; Zhao, X.-d.; Liu, J.; Wang, X.; Gui, T.-J.; Li, B.-J.; Tang, Y.-Z.; et al. Study on graphene modified organic anti-corrosion coatings: A comprehensive review. J. Alloys Compd. 2019, 806, 611–635. [Google Scholar] [CrossRef]
  22. Seel, M.; Pandey, R. Proton and hydrogen transport through two-dimensional monolayers. 2D Mater. 2016, 3, 025004. [Google Scholar] [CrossRef]
  23. Prasai, D.; Tuberquia, J.C.; Harl, R.R.; Jennings, G.K.; Bolotin, K.I. Graphene: Corrosion-inhibiting coating. ACS Nano 2012, 6, 1102–1108. [Google Scholar] [CrossRef] [PubMed]
  24. Zhao, Z.; Hou, T.; Wu, N.; Jiao, S.; Zhou, K.; Yin, J.; Suk, J.W.; Cui, X.; Zhang, M.; Li, S.; et al. Polycrystalline Few-Layer Graphene as a Durable Anticorrosion Film for Copper. Nano Lett. 2021, 21, 1161–1168. [Google Scholar] [CrossRef] [PubMed]
  25. Bohm, S. Graphene against corrosion. Nat. Nanotechnol. 2014, 9, 741–742. [Google Scholar] [CrossRef] [PubMed]
  26. Cui, C.; Lim, A.T.O.; Huang, J. A cautionary note on graphene anti-corrosion coatings. Nat. Nanotechnol. 2017, 12, 834–835. [Google Scholar] [CrossRef] [PubMed]
  27. Zhang, Y.; Sun, J.; Xiao, X.; Wang, N.; Meng, G.; Gu, L. Graphene-like two-dimensional nanosheets-based anticorrosive coatings: A review. J. Mater. Sci. Technol. 2022, 129, 139–162. [Google Scholar] [CrossRef]
  28. Nurdiwijayanto, L.; Nishijima, H.; Miyake, Y.; Sakai, N.; Osada, M.; Sasaki, T.; Taniguchi, T. Solution-Processed Two-Dimensional Metal Oxide Anticorrosion Nanocoating. Nano Lett. 2021, 21, 7044–7049. [Google Scholar] [CrossRef]
  29. Shi, K.; Meng, X.; Xiao, S.; Chen, G.; Wu, H.; Zhou, C.; Jiang, S.; Chu, P.K. MXene Coatings: Novel Hydrogen Permeation Barriers for Pipe Steels. Nanomaterials 2021, 11, 2737. [Google Scholar] [CrossRef]
  30. Mujib, S.B.; Mukherjee, S.; Ren, Z.; Singh, G. Assessing corrosion resistance of two-dimensional nanomaterial-based coatings on stainless steel substrates. R. Soc. Open Sci. 2020, 7, 200214. [Google Scholar] [CrossRef]
  31. Shen, L.; Zhao, W.; Wang, K.; Xu, J. GO-Ti3C2 two-dimensional heterojunction nanomaterial for anticorrosion enhancement of epoxy zinc-rich coatings. J. Hazard. Mater. 2021, 417, 126048. [Google Scholar] [CrossRef] [PubMed]
  32. Xi, K.; Wu, H.; Zhou, C.; Qi, Z.; Yang, K.; Fu, R.K.Y.; Xiao, S.; Wu, G.; Ding, K.; Chen, G.; et al. Improved corrosion and wear resistance of micro-arc oxidation coatings on the 2024 aluminum alloy by incorporation of quasi-two-dimensional sericite microplates. Appl. Surf. Sci. 2022, 585, 152693. [Google Scholar] [CrossRef]
  33. Wang, X. Preparation and Corrosion Resistance of AKT-Waterborne Polyurethane Coating. Int. J. Electrochem. Sci. 2020, 15, 1450–1464. [Google Scholar] [CrossRef]
  34. Kavimani, V.; Prakash, K.S.; Gunashri, R.; Sathish, P. Corrosion protection behaviour of r-GO/TiO2 hybrid composite coating on Magnesium substrate in 3.5 wt.% NaCl. Prog. Org. Coat. 2018, 125, 358–364. [Google Scholar] [CrossRef]
  35. Li, Z.; Ding, S.; Kong, L.; Wang, X.; Ashour, A.; Han, B.; Ou, J. Nano TiO2-engineered anti-corrosion concrete for sewage system. J. Clean. Prod. 2022, 337, 130508. [Google Scholar] [CrossRef]
  36. Kumar, A.M.; Khan, A.; Hussein, M.A.; Khan, M.Y.; Dafalla, H.; Suresh, B.; Ramakrishna, S. Hybrid nanocomposite coatings from PEDOT and BN-TiO2 nanosheets: Enhanced invitro corrosion resistance, wettability and biocompatibility for biomedical applications. Prog. Org. Coat. 2022, 170, 106946. [Google Scholar] [CrossRef]
  37. Zhang, Y.; Zhang, K.; Lei, S.; Su, Y.; Yang, W.; Wang, J.; Qin, G.; Li, W. Formation and oxidation behavior of TiO2 modified Al2O3-Nb2O5/NbAl3 composite coating prepared by two-step methods. Surf. Coat. Technol. 2022, 433, 128081. [Google Scholar] [CrossRef]
  38. Devikala, S.; Kamaraj, P.; Arthanareeswari, M. Corrosion resistance behavior of PVA/TiO2 composite in 3.5% NaCl. Mater. Today Proc. 2018, 5, 8672–8677. [Google Scholar] [CrossRef]
  39. Rostami, S.; Mahdavi, S.; Alinezhadfar, M.; Mohseni, A. Tribological and corrosion behavior of electrochemically deposited Co/TiO2 micro/nano-composite coatings. Surf. Coat. Technol. 2021, 423, 127591. [Google Scholar] [CrossRef]
  40. Anwar, S.; Khan, F.; Zhang, Y. Corrosion behaviour of Zn-Ni alloy and Zn-Ni-nano-TiO2 composite coatings electrodeposited from ammonium citrate baths. Process. Saf. Environ. Prot. 2020, 141, 366–379. [Google Scholar] [CrossRef]
  41. Wang, K.; Wang, J.; Fan, J.; Lotya, M.; O’Neill, A.; Fox, D.; Feng, Y.; Zhang, X.; Jiang, B.; Zhao, Q.; et al. Ultrafast saturable absorption of two-dimensional MoS2 nanosheets. ACS Nano 2013, 7, 9260–9267. [Google Scholar] [CrossRef]
  42. Asan, G.; Asan, A.; Çelikkan, H. The effect of 2D-MoS2 doped polypyrrole coatings on brass corrosion. J. Mol. Struct. 2020, 1203, 127318. [Google Scholar] [CrossRef]
  43. Xia, Y.; He, Y.; Chen, C.; Wu, Y.; Chen, J. MoS2 nanosheets modified SiO2 to enhance the anticorrosive and mechanical performance of epoxy coating. Prog. Org. Coat. 2019, 132, 316–327. [Google Scholar] [CrossRef]
  44. Hu, S.; Muhammad, M.; Wang, M.; Ma, R.; Du, A.; Fan, Y.; Cao, X.; Zhao, X. Corrosion resistance performance of nano-MoS2-containing zinc phosphate coating on Q235 steel. Mater. Lett. 2020, 265, 127256. [Google Scholar] [CrossRef]
  45. Chen, C.; He, Y.; Xiao, G.; Xia, Y.; Li, H.; He, Z. Two-dimensional hybrid materials: MoS2-RGO nanocomposites enhanced the barrier properties of epoxy coating. Appl. Surf. Sci. 2018, 444, 511–521. [Google Scholar] [CrossRef]
  46. Sasaki, T.; Kooli, F.; Iida, M.; Michiue, Y.; Takenouchi, S.; Yajima, Y.; Izumi, F.; Chakoumakos, B.C.; Watanabe, M. A Mixed Alkali Metal Titanate with the Lepidocrocite-like Layered Structure. Preparation, Crystal Structure, Protonic Form, and Acid−Base Intercalation Properties. Chem. Mater. 1998, 10, 4123–4128. [Google Scholar] [CrossRef]
  47. Zhang, Z.; Li, W.; Yuen, M.F.; Ng, T.-W.; Tang, Y.; Lee, C.-S.; Chen, X.; Zhang, W. Hierarchical composite structure of few-layers MoS2 nanosheets supported by vertical graphene on carbon cloth for high-performance hydrogen evolution reaction. Nano Energy 2015, 18, 196–204. [Google Scholar] [CrossRef]
  48. Singh, S.; Singh, G.; Bala, N. Corrosion behavior and characterization of HA/Fe3O4/CS composite coatings on AZ91 Mg alloy by electrophoretic deposition. Mater. Chem. Phys. 2019, 237, 121884. [Google Scholar] [CrossRef]
  49. Hu, S.; Li, W.; Finklea, H.; Liu, X. A review of electrophoretic deposition of metal oxides and its application in solid oxide fuel cells. Adv. Colloid Interface Sci. 2020, 276, 102102. [Google Scholar] [CrossRef] [PubMed]
  50. Hoshide, T.; Zheng, Y.; Hou, J.; Wang, Z.; Li, Q.; Zhao, Z.; Ma, R.; Sasaki, T.; Geng, F. Flexible Lithium-Ion Fiber Battery by the Regular Stacking of Two-Dimensional Titanium Oxide Nanosheets Hybridized with Reduced Graphene Oxide. Nano Lett. 2017, 17, 3543–3549. [Google Scholar] [CrossRef]
  51. Maluangnont, T.; Matsuba, K.; Geng, F.; Ma, R.; Yamauchi, Y.; Sasaki, T. Osmotic Swelling of Layered Compounds as a Route to Producing High-Quality Two-Dimensional Materials. A Comparative Study of Tetramethylammonium versus Tetrabutylammonium Cation in a Lepidocrocite-type Titanate. Chem. Mater. 2013, 25, 3137–3146. [Google Scholar] [CrossRef]
  52. Peng, F.; Zhang, D.; Liu, X.; Zhang, Y. Recent progress in superhydrophobic coating on Mg alloys: A general review. J. Magnes. Alloy. 2021, 9, 1471–1486. [Google Scholar] [CrossRef]
  53. Zhang, M.; Xu, H.; Zeze, A.L.P.; Liu, X.; Tao, M. Coating performance, durability and anti-corrosion mechanism of organic modified geopolymer composite for marine concrete protection. Cem. Concr. Compos. 2022, 129, 104495. [Google Scholar] [CrossRef]
  54. Gong, C.; Jianzhong, L.; Cuicui, C.; Changfeng, L.; Liang, S. Study on silane impregnation for protection of high performance concrete. Procedia Eng. 2012, 27, 301–307. [Google Scholar] [CrossRef] [Green Version]
  55. Wang, S.; Wang, Y.; Zou, Y.; Wu, Y.; Chen, G.; Ouyang, J.; Jia, D.; Zhou, Y. A self-adjusting PTFE/TiO2 hydrophobic double-layer coating for corrosion resistance and electrical insulation. Chem. Eng. J. 2020, 402, 126116. [Google Scholar] [CrossRef]
  56. Parichehr, R.; Dehghanian, C.; Nikbakht, A. Preparation of PEO/silane composite coating on AZ31 magnesium alloy and investigation of its properties. J. Alloys Compd. 2021, 876, 159995. [Google Scholar] [CrossRef]
  57. Wu, C.; Liu, Q.; Chen, R.; Liu, J.; Zhang, H.; Li, R.; Takahashi, K.; Liu, P.; Wang, J. Fabrication of ZIF-8@SiO2 Micro/Nano Hierarchical Superhydrophobic Surface on AZ31 Magnesium Alloy with Impressive Corrosion Resistance and Abrasion Resistance. ACS Appl. Mater. Interfaces 2017, 9, 11106–11115. [Google Scholar] [CrossRef]
  58. Zhang, G.; Qin, S.; Yan, L.; Zhang, X. Simultaneous improvement of electromagnetic shielding effectiveness and corrosion resistance in magnesium alloys by electropulsing. Mater. Charact. 2021, 174, 111042. [Google Scholar] [CrossRef]
  59. Liu, H.; Tong, Z.; Zhou, W.; Yang, Y.; Jiao, J.; Ren, X. Improving electrochemical corrosion properties of AZ31 magnesium alloy via phosphate conversion with laser shock peening pretreatment. J. Alloys Compd. 2020, 846, 155837. [Google Scholar] [CrossRef]
Coatings 12 01488 g001 550
Figure 1. Zeta potential diagram of TiO2 and MoS2.
Figure 1. Zeta potential diagram of TiO2 and MoS2.
Coatings 12 01488 g001
Coatings 12 01488 g002 550
Figure 2. SEM images of films deposited on AZ31B: (a,b) TiO2, (c,d) MoS2, (e) TiO2/MoS2, (f) TiO2/MoS2-K.
Figure 2. SEM images of films deposited on AZ31B: (a,b) TiO2, (c,d) MoS2, (e) TiO2/MoS2, (f) TiO2/MoS2-K.
Coatings 12 01488 g002
Coatings 12 01488 g003 550
Figure 3. XRD patterns of magnesium alloy, TiO2, MoS2, and TiO2/MoS2 films.
Figure 3. XRD patterns of magnesium alloy, TiO2, MoS2, and TiO2/MoS2 films.
Coatings 12 01488 g003
Coatings 12 01488 g004 550
Figure 4. XPS spectra of TiO2/MoS2: (a) Ti 2p, (b) O 1s, (c) Mo 3d, (d) S 2p.
Figure 4. XPS spectra of TiO2/MoS2: (a) Ti 2p, (b) O 1s, (c) Mo 3d, (d) S 2p.
Coatings 12 01488 g004
Coatings 12 01488 g005 550
Figure 5. (a) Contact angles of magnesium alloy, TiO2/MoS2, and TiO2/MoS2-K; (b) FT-IR spectra of TiO2/MoS2 and TiO2/MoS2-K.
Figure 5. (a) Contact angles of magnesium alloy, TiO2/MoS2, and TiO2/MoS2-K; (b) FT-IR spectra of TiO2/MoS2 and TiO2/MoS2-K.
Coatings 12 01488 g005
Coatings 12 01488 g006 550
Figure 6. Polarization curves of magnesium alloy, TiO2, MoS2, TiO2/MoS2, TiO2/MoS2-K.
Figure 6. Polarization curves of magnesium alloy, TiO2, MoS2, TiO2/MoS2, TiO2/MoS2-K.
Coatings 12 01488 g006
Coatings 12 01488 g007 550
Figure 7. Electrochemical impedance spectroscopy of magnesium alloy, TiO2, TiO2/MoS2-K.
Figure 7. Electrochemical impedance spectroscopy of magnesium alloy, TiO2, TiO2/MoS2-K.
Coatings 12 01488 g007
Coatings 12 01488 g008 550
Figure 8. Equivalent circuits for EIS spectra: (a) magnesium alloy, (b) TiO2 thin film and TiO2/MoS2-K thin film.
Figure 8. Equivalent circuits for EIS spectra: (a) magnesium alloy, (b) TiO2 thin film and TiO2/MoS2-K thin film.
Coatings 12 01488 g008
Coatings 12 01488 g009 550
Figure 9. The microstructure of the sample surface after salt spray test at different times. Magnesium alloy: (a) 24 h, (b) 48 h, (c) 72 h; TiO2 film: (e) 24 h, (f) 48 h, (g) 72 h; TiO2/MoS2-K film: (i) 24 h, (j) 48 h, (k) 72 h. The (d,h,l) insets are partial enlargements of (c,g,k), respectively.
Figure 9. The microstructure of the sample surface after salt spray test at different times. Magnesium alloy: (a) 24 h, (b) 48 h, (c) 72 h; TiO2 film: (e) 24 h, (f) 48 h, (g) 72 h; TiO2/MoS2-K film: (i) 24 h, (j) 48 h, (k) 72 h. The (d,h,l) insets are partial enlargements of (c,g,k), respectively.
Coatings 12 01488 g009
Coatings 12 01488 g010 550
Figure 10. Salt spray corrosion weight gain diagram.
Figure 10. Salt spray corrosion weight gain diagram.
Coatings 12 01488 g010
Table
Table 1. Electronegativity of TiO2 and MoS2.
Table 1. Electronegativity of TiO2 and MoS2.
SampleZeta Potential/mV
TiO2−0.511
MoS2−0.356
Table
Table 2. Potentiodynamic polarization curves of samples in 3.5 wt % NaCl aqueous solution.
Table 2. Potentiodynamic polarization curves of samples in 3.5 wt % NaCl aqueous solution.
SampleEcorr/(VAg/AgCl)Icorr/(A·cm−2)
Magnesium alloy−1.476.81 × 10−4
TiO2−1.345.31 × 10−6
MoS2−1.112.19 × 10−5
TiO2/MoS2−1.003.69 × 10−7
TiO2/MoS2-K−0.856.73 × 10−8
Table
Table 3. Electrochemical data extracted from ECs fitting of the EIS curves.
Table 3. Electrochemical data extracted from ECs fitting of the EIS curves.
SampleRs
(Ω·cm2)		CPEfilm
(F/cm2)		Rp
(Ω·cm2)		CPEdl-T
(F/cm2)		CPEdl-P
(F/cm2)		Rct
(Ω·cm2)
Magnesium alloy10.2--7.11 × 10−6-111.9
TiO28.971.27 × 10−616.961.66 × 10−60.98659.6
TiO2/MoS2-K9.258.92 × 10−619.291.87 × 10−60.95871.9
Table
Table 4. Energy spectrum analysis of neutral salt spray test products (at. %).
Table 4. Energy spectrum analysis of neutral salt spray test products (at. %).
PointOMgMnTiNaClMoS
A57.6426.1812.0202.791.3700
B59.2325.4311.0802.511.7500
C55.3825.2812.602.403.151.1900
D53.8525.3211.063.993.981.8000
E55.6225.1611.103.692.171.120.220.92
F56.3825.0911.202.572.231.330.191.01
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

Lai, L.; Wu, H.; Mao, G.; Li, Z.; Zhang, L.; Liu, Q. Microstructure and Corrosion Resistance of Two-Dimensional TiO2/MoS2 Hydrophobic Coating on AZ31B Magnesium Alloy. Coatings 2022, 12, 1488. https://doi.org/10.3390/coatings12101488

AMA Style

Lai L, Wu H, Mao G, Li Z, Zhang L, Liu Q. Microstructure and Corrosion Resistance of Two-Dimensional TiO2/MoS2 Hydrophobic Coating on AZ31B Magnesium Alloy. Coatings. 2022; 12(10):1488. https://doi.org/10.3390/coatings12101488

Chicago/Turabian Style

Lai, Longjie, Heng Wu, Guobing Mao, Zhengdao Li, Li Zhang, and Qi Liu. 2022. "Microstructure and Corrosion Resistance of Two-Dimensional TiO2/MoS2 Hydrophobic Coating on AZ31B Magnesium Alloy" Coatings 12, no. 10: 1488. https://doi.org/10.3390/coatings12101488

APA Style

Lai, L., Wu, H., Mao, G., Li, Z., Zhang, L., & Liu, Q. (2022). Microstructure and Corrosion Resistance of Two-Dimensional TiO2/MoS2 Hydrophobic Coating on AZ31B Magnesium Alloy. Coatings, 12(10), 1488. https://doi.org/10.3390/coatings12101488

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop