Simultaneously Improving the Anticorrosion and Antiscratch

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Materials and Interfaces

Simultaneously improving the anti-corrosion and anti-scratch performance of epoxy coatings with graphite fluoride via large-scale preparation Fan Lei, Bingyu wu, Haoyang Sun, Feng jiang, Junlong Yang, and Dazhi Sun Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.8b04405 • Publication Date (Web): 20 Nov 2018 Downloaded from http://pubs.acs.org on November 22, 2018

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Industrial & Engineering Chemistry Research

Simultaneously improving the anti-corrosion and anti-scratch performance of epoxy coatings with graphite fluoride via large-scale preparation Fan Lei, Bingyu Wu, Haoyang Sun, Feng Jiang, Junlong Yang, Dazhi Sun* Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China KEYWORDS: epoxy, coating, graphite fluoride, corrosion protection, scratch resistance

ABSTRACT: Hydrophobic graphite fluoride (GrF) reinforced epoxy coatings are fabricated on steel substrate with a simple, solventless and surfactant-free approach. The contact angle can be enhanced from 72o to 103o after the introduction of 1 wt% GrF to epoxy, suggesting the superior hydrophobic surface. The composite coatings on steel substrate exhibit the prominent corrosion protection performance as revealed by electrochemical impedance spectroscopy. The mechanism responsible for the corrosion resistance enhancement can be attributed to the synergistic effects of electrical insulating, water repellent and barrier properties, resulted from the well-dispersed superhydrophobic GrF platelets in epoxy matrix. Moreover, 1 wt% GrF/epoxy coatings also present significant scratch resistance performance due to the uniform dispersion of the inorganic platelets and the enhanced storage modulus. The results indicate that constructing GrF/epoxy

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coatings with improved corrosion protection and scratch resistance property is capable of preventing metals suffering from corrosion attack and crack damages with a scalable fashion.

1. INTRODUCTION Owing to its strong cohesive strength and intense adhesion to the substrate, epoxy coatings have been widely used in glass, plastic and metal protections 1-3. In terms of protecting metals against harsh corrosive environments, the primary function of epoxy coatings is to act as a physical barrier layer against the corrosive moieties, such as oxygen, water and corrosive ions 4-6. However, epoxy coatings are also accompanied with several weakness, such as low crack resistance, high brittleness, and inadequate physical barrier performance to corrosive medium 7-9. Consequently, the neat epoxy coating usually cannot meet the ever-increasing stringent demands for metal protections and modification is needed to further enhance the anti-corrosion performance. Recently, epoxy matrix incorporated with layered nanoplatelets as the reinforcements have attracted significant attraction from both scientific research and practical applications due to their excellent mechanical performance 10-17, gas barrier 18-19, fire retardation 20-21, thermal conductivity 22 and so on. The enhanced barrier performance against water, oxygen and corrosive ions, generally allows for the great improved corrosion prevention performance 23-26. Li and coworkers reported on the preparation of highly effective anti-corrosion epoxy spray coating containing self-assembled clay in smectic order 3. The well-dispersed epoxy/clay coatings exhibited advanced corrosion protection of aluminium alloy as compared with the neat epoxy, which is ascribed that the constructed nanocomposite coatings own excellent barrier performance against water and oxygen. Chang et al demonstrated the improved gas barrier performance accompanied with the hydrophobic property of epoxy/graphene coating was able to further


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provide a remarkable corrosion protection effect on cold-rolled steel 27. Furthermore, Chen et al. prepared graphene/epoxy anticorrosive coatings through the utilization of poly(2-butylaniline) (P2BA) as the noncovalent dispersant 4. The improved anticorrosion performance was resulted from the synergistic effects of the redox catalytic capability of P2BA, excellent mechanical and barrier performance of the well-dispersed graphene nanosheets in the epoxy matrix. Unfortunately, many researchers used solvents and surfactants to acquire good dispersion of layered nanoplatelets embedded in epoxy matrix 4, 9, 28, which is environmentally hazardous and limits their large-scale industrial applications. Besides, it is unavoidable to cause the decrease in glass transition temperature of the polymer matrices because of the introduction of low molecular weight supplements 2, 29-30. Compared with clay, graphite fluoride (GrF), as one of the graphite derivatives, is a novel twodimensional inorganic platelet with superior physical properties. GrF is one of the lowest surface energy materials known, which results in its remarkable lubrication performance 31-33. In our pervious study, it was demonstrated that GrF is able to form hydrogen bonding with polyamide 6 (PA6) 34 and epoxy 35, thus improving the dispersion of GrF in polymeric matrix without the help of surfactant and solvent. Consequently, the mechanical property of PA6 and epoxy are significantly enhanced at low concentration of GrF due to the strong interface interaction between GrF and polymer matrix. With its two-dimensional structure, the incorporation of GrF into epoxy coating are supposed to create “tortuous pathway” and prolong penetration paths for the oxygen, water, ions and electrolytes transport, thus enhancing the physical barrier performance. On the other hand, with its low surface energy, the addition of GrF into epoxy matrix is beneficial for fabricating hydrophobic coating, which further enhance the physical barrier effects 27, 36-38. Therefore, it is hypothesized that the incorporation of GrF into epoxy


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coating is capable of providing an effective barrier layer to protect the steel substrate from corrosive medium attacking. Besides the anti-corrosion property, anti-scratch performance is of equal importance for the practical application of metal protection owing to the inevitable scratch damages on coatings in use. The improved anti-scratch property can make great contribution to extend life service of metal protection coating 39. It has been reported that two-dimensional inorganic platelets are generally used for preparing polymer coating with high scratch resistance performance 2, 40-41. Sue et al. indicated that the incorporation of α-zirconium phosphates (ZrP) nanoplatelets into epoxy coating is able to delay microcracking and plowing damage, and remarkably reduce scratch coefficient of friction due to the well dispersion of ZrP 2. However, due to the introduction of low molecular weight surfactant that is used for dispersing ZrP nanoplatelets in solvent, the glass transition temperature of composites coating is severely decreased, which limits its practical applications. Hence, in this study, we developed an environmentally friendly process to fabricate anticorrosion coatings with excellent anti-scratch performance. Due to hydrogen bonding interaction between GrF platelets and curing agent, the GrF/epoxy composite coatings are directly fabricated by blending GrF platelets and curing agent, following by mixing with epoxy resin without involving any solvent and surfactant modification, and a good dispersion of GrF in epoxy matrix can be simply achieved. The influence of GrF concentration on the anti-corrosion and antiscratch performance of the prepared composite coatings on steel substrate is carefully investigated. The detailed protection mechanisms are evaluated based on the electrochemical corrosion measurements and nanoscratch tests. 2. EXPERIMENTAL SECTION


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2.1 Materials A commercial Epoxy 44 (E-44) resin was bought from Shenzhen Jitian Chemical corporation. Polyetheramine D230 (D230) aliphatic curing agent was purchased from Aladdin Chemical Corporation. Graphite fluoride (GrF) with C: F = ~1:1 was supplied from Shenyang Xi Fu technology Co., Ltd. These materials were directly used as received. 2.2 Preparation of coating and film samples The typical procedure for the preparation of GrF/epoxy coating is as follows. Regarding to the 3 wt% GrF/epoxy coating, 0.63g GrF was added to 5.13g D230, and the whole suspension was stirred for at least 2h and sonicated for 0.5h. Then 15.13g epoxy was added to obtain a homogenous mixture. After mixing, the mixture was degassed in a rotary evaporator at 70 oC to remove the trapped air bubbles and the obtained suspension mixture is prepared for coating samples. Before coating, the Q235 steel electrode surface was polished using 400 grit sandpaper to remove possible residual rust products. After surface treatment, the 3 wt% GrF/epoxy suspensions were cast onto the Q235 steel substrate by a laboratory casting machine (MSKAFA-L800, Hefei Kejing Materials Technology Co., Ltd.). The coated steel samples were cured at 70 oC for 24h. For different concentrations of GrF fillers in the epoxy coatings, they are prepared through the similar procedure and denoted as 0.5%, 1%, 3% GrF/epoxy, respectively. Regrading to the neat epoxy and composites thin films, the prepared process is consistent with the above procedure through replacing Q235 steel substrate with polyethylene terephthalate (PET) films. And the free-standing films were acquired by peeling them off from PET substrate. The thickness of the prepared coating and thin film is controlled to around 50 µm. 2.3 Characterizations


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In order to observe the dispersion state of GrF platelets in the epoxy coating matrix, the thin films with pre-crack are quenched in liquid nitrogen and then brittle fractured to obtain the smooth surface. The fracture surfaces of the GrF/epoxy coatings and Q235 carbon steel surfaces were directly observed by scanning electron microscopy (SEM, VEGA 3 LMH, Tescan Co., Ltd) with an accelerating voltage of 10 kV. Before SEM measurements, the fracture surfaces of thin films were coated with a thin layer of platinum by ion sputtering. Thermo-mechanical properties of epoxy and GrF/epoxy thin films were investigated by dynamic mechanical analysis (DMA 8000, PerkinElmer, USA) through a tensile mode. The temperature was ranged from 30 oC to 120 oC at a frequency of 1 Hz, with a heating rate of 3 oC/min, and a strain of 0.05%. The glass transition temperature (Tg) was obtained from the curves of tan as a function of temperature. The transparency of different GrF/epoxy thin films was conducted using a Lambda 950 UV-visNIR spectrophotometer (PerkinElmer, USA). Surface roughness of neat epoxy coating and composites coating are measured using a 3D optical microscope (ContourGT-K, Bruker). The contact angle was measured by a contact angle meter (VCA optima, USA) with deionized water droplets of about 3 l at room temperature. The contact angle was obtained at five different locations for each sample to obtain the mean value. Water absorption of GrF/epoxy was measured according to ASTM D570 through weighing the mass of the thin film sample at stipulated time intervals. The specimens were removed from the water bath, quickly dried with non-woven fabrics and weighed. The water absorption (Mt) was then determined by the following equation 𝑀𝑡 =

𝑊𝑤𝑒𝑡 ― 𝑊𝑑𝑟𝑦 𝑊𝑑𝑟𝑦

× 100%

Corrosion protection properties of GrF/epoxy composites were performed by electrochemical impedance spectroscopy (EIS) analysis. The electrochemical corrosion test was conducted in 3.5


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wt% NaCl solution on electrochemical workstation, including Platinum as counter electrode, saturated calomel electrode (SCE) as reference electrode and coated steel specimen as working electrode. EIS measurement was carried out at the frequency range from 10 kHz to 10 mHz with 20 mV amplitude sinusoidal voltage. EIS analysis was conducted on 1 cm2 of the coated samples and the tests were performed for 3 times to ensure the repeatability of the measurements. The final corrosion parameters from EIS data were analyzed using the Zview software. The nanoscratch test was carried out on the Nano Indenter G200 with a diamond Berkovich tip. The scratch load was linearly increased from 0 mN to 5 mN at a constant scratch velocity of 30 µm/s with a scratch distance of 500 µm. The effective penetration scratch depth during the scratch and the residual scratch depth after scratch tests were obtained and plotted vs. the scratch distance. At least nine tests were performed on each sample to acquire more consistent results. The scratch load for obtaining the cross profile of the scratch path is 3 mN. The elastic and plastic deformation values are calculated based on Figure 1. As illustrated in Figure 1, the elastic deformation is the ratio of the area of elastic work to the whole area of plastic and elastic work. And the plastic deformation is the ratio of the area of plastic work to the whole area of plastic and elastic work.


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Figure 1. The schematic representation of loading and unloading curve during the scratch test.

3. RESULTS AND DISCUSSION 3.1 Characterization of GrF and GrF/epoxy coatings. The surface morphology of the used GrF platelets is indicated in Figure 2. As observed, GrF platelets prefer to stack together and develop laminated structure with a thickness of ~330 nm and an average size of ~5 µm. Thanks to the intercalation of fluorine atoms between the laminated structure of GrF platelets, it is easy for GrF to slide against each other42. In addition, it is demonstrated that GrF can be well-dispersed in epoxy matrix due to the hydrogen bonding between GrF filler and aliphatic amine curing agent 35.


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Figure 2. The scanning electron microscopy images of GrF platelets.

The dispersion state of GrF platelets in the epoxy coating matrix was investigated by SEM, which are shown in Figure 3. Before SEM morphology measurements, all the free-standing thin films were brittle fractured in liquid nitrogen in order to acquire the smooth surface. As clearly observed in Figure 3a, the fracture surface of the neat epoxy coating is quite smooth due to the poor resistance of epoxy to crack initiation and plastic deformation resulted from the high degree of crosslinking 7. At low concentrations of GrF (0.5% and 1%), the fracture surfaces of the composites are a little bit smooth and GrF are well-dispersed in the epoxy coatings. With increasing the concentration of GrF to 3%, the fracture surface is much rough and many large GrF agglomerations can be observed in the epoxy matrix, indicating the poor dispersion of GrF platelets at a high loading. The results are well consistent with our previous study in GrF reinforced polyamide 6 matrix 34.


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Figure 3. SEM images of fracture surfaces of (a, b) epoxy, and GrF/epoxy composites at different GrF loading of (c, d) 0.5%, (e, f) 1% and (g, h) 3%. The white arrows represent GrF platelets in the epoxy matrix.


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The thermo-mechanical behaviors of the neat epoxy and GrF/epoxy thin films were investigated using standard DMA measurements for characterizing their temperature-dependent mechanical properties. Figure 4 provides the specific information about storage modulus and Tan δ as a function of time. The storage modulus represents the ability of the epoxy composites to store elastic energy. As observed, throughout the investigated temperature range, the low GrF loading in epoxy matrix, such as 0.5% and 1%, can effectively enhance the storage modulus, which is attributed to the well-dispersion of GrF, and suppression and hindrance of the molecular mobility of the matrices by the incorporation of inorganic platelet materials 43. However, with further increasing the GrF concentration to 3%, the storage modulus experiences a decrease trend but is still higher than that of the neat epoxy. It can be attributed to the fact that, at a high concentration of GrF (3%), the poor dispersion and large aggregations of GrF embedded in epoxy weakens the interface interaction between GrF platelets and epoxy matrix. The glass transition temperature Tg, which is defined by the temperature corresponding to the peak value of tan δ, is another important parameter for characterizing epoxy materials. As observed in Figure 4b, Tg of the GrF/epoxy composites exhibits a slight increase compared with that of the neat epoxy, indicating no obvious decrease in Tg in our GrF/epoxy composite system due to our surfactant-free process. The Tg improvements of the GrF/epoxy composites can be attributed to the fact that the multi-linkage of fillers with epoxy matrix can effectively confine the polymer chain movements 44-45.


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Figure 4. DMA plots of the neat epoxy and GrF/epoxy thin film (a) storage modulus as a function of temperature. (b) Tan δ as a function of temperature.

The optical transmittance spectra of the neat epoxy as well as the GrF/epoxy composite films are shown in Figure 5. As observed in Figure 5a, the transparency of the films with GrF loading below 1% is almost the same as that of the neat epoxy, which indicates the uniform dispersion of GrF in epoxy matrix and no micro-size GrF aggregations present. However, with the incorporation of 3% GrF in epoxy matrix, the transparency of the film shows a significant drop. this phenomenon is attributed to the poor dispersion and the formation of large GrF aggregates which cause more light scattering. The images shown in Figure 5b indicate that the GrF/epoxy thin films with loading of 0.5% and 1% GrF platelets are nearly colorless and exhibit great optical transparencies. The transparency of the composites with 0.5% and 1% GrF at 550 nm is above 85%, which also qualifies for flexible electronics packaging coating protections 46. However, the 3% GrF/epoxy thin film becomes grayish due to the presence of large GrF aggregations. The above results illustrate that GrF platelets at the loading of 0.5% and 1% can be well-dispersed in epoxy matrix, and GrF platelets will spontaneously aggregate at a higher


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concentration (i.e. 3%). The GrF aggregates can also affect the anti-corrosion and anti-scratch performance of the coating, as well, which will be discussed later.

Figure 5. (a) The transparency of the neat epoxy, GrF/epoxy thin film. (b) images show the transparency of the thin films when the films and the picture underneath are direct contact with each other.

Generally, the water repellent performance and water transportation through the organic coatings is the primary cause of coating failure. In order to detect the influence of GrF concentration on the surface wettability of epoxy, the contact angle results are illustrated in Figure 6a. As shown, the contact angle of the neat epoxy is about 72o due to its hydrophilicity. After the incorporation of hydrophobic GrF platelets, the contact angle of composites can be substantially improved. With the loading of 1% GrF platelets, the contact angle of composites can be as high as 103o, suggesting the superior hydrophobic surface of GrF/epoxy compared with the neat epoxy due to the superhydrophobic nature of GrF. During the film formation, the units of fluorinated atoms in GrF structure preferentially migrates to the external surface of coating,


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leading to a more hydrophobic surface containing a high fluorine content 45. Apparently, the hydrophobicity is beneficial for repelling the moisture, further reducing the water and corrosive moieties adsorption on the coating surface, finally preventing the underlying steel substrate from corrosion attack. Besides, the water absorption of the neat epoxy and GrF/epoxy thin film are obtained through the weight change before and after immersing in the deionized water. As shown in Figure 6b, the saturation for all epoxy samples is reached after 9 days. The water uptake of the neat epoxy at saturation is about 1.19 wt%, which is much higher than those of GrF/epoxy composites. The water absorption of 0.5%, 1%, 3% GrF/epoxy is 0.88 wt%, 0.61 wt%, 0.46 wt%, respectively, indicating that the introduction of GrF can effectively reduce the water absorption of composites. It should be noted there that the hydrophobicity of 3% GrF/epoxy slightly is lesser than that of 1% GrF/epoxy. The reason can be attributed to the poor dispersion of GrF platelets at a high loading, which decreases the hydrophobicity. The water absorption of 3% GrF/epoxy is also lower than that of 1% GrF/epoxy, which can be resulted from the high weight concentration of GrF into epoxy reducing the water absorption and transportation. The reduced water absorption of composites is due to the following two reasons: (1) The addition of superhydrophobic GrF platelets into epoxy matrix decrease the penetration and absorption of water in the composites; (2) The well-dispersed two-dimensional GrF platelets in epoxy matrix is able to fabricate a tortuous path for preventing water, oxygen and electrolyte penetrating through the composites. The improved hydrophobicity and the reduced media transportation through the organic coatings are supposed to enhance the corrosion resistance performance.


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Figure 6. (a) Contact angle and (b) water uptake for the neat epoxy, GrF/epoxy thin films.

3.2 Anti-corrosion properties of GrF/epoxy coatings on steel substrate. Electrochemical impedance spectroscopy (EIS) measurement is used to understand the protective nature of the coatings. The Bode plots of bare steel, the neat epoxy and GrF/epoxy with different concentration of GrF coated on steel substrate are exhibited in Figure 7. The impedance modulus at the lowest frequency in Bode plot is usually used to determine the resistance of the coating to the transportation of electrons and charges. As shown in Figure 7a, it is clearly observed that after the introduction of the neat epoxy coating, the impedance modulus at the lowest frequency exhibits a five orders of magnitude increase compared with that of the bare steel. With the incorporation of GrF platelets into epoxy coating, the impedance modulus experiences a gradual increase. And the composites coating with 1% GrF platelets owns the highest impedance modulus, indicating that the 1% GrF/epoxy composite coating has the best corrosion resistance performance to the steel substrate. Besides, the best anti-corrosion behavior of 1% GrF/epoxy composites can also be reflected by the higher phase angles at low frequency compared with that of other coating, which is illustrated in Figure 7b. At a high frequency, the


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corresponding phase angles of composites coating are almost -90o, which suggests that the coatings act as a perfect capacitor. Moreover, one time constant is found in the impedance spectra of different coatings, further demonstrating the barrier characteristics of composites coatings.

Figure 7. Bode plots of bare steel, the neat epoxy and GrF/epoxy with different concentration of GrF coated on steel substrate.

The EIS results are further fitted by Zview software based on the equivalent electric circuits. As stated above, all the unbroken coating exhibits one time constant at the initial stage of immersion. In the inserted equivalent circuits indicated in Figure 8, Rs is the solution resistance, Rc is the coating resistance, Cc is the coating capacitance 25, 47. The higher Rc suggests that the coating has better resistance ability to the transportation of electrons and charges. As observed from the fitted electrochemical results shown in Figure 8, Rc of the neat epoxy coating is 8.5 × 107 ohm.cm2. After the introduction of 0.5%, 1%, 3% GrF platelets, the coating resistance of composites is 8.6 × 108, 2.43 × 109, 1.9 × 109 ohm.cm2, respectively. The resistance of composites coating with 1% GrF platelets still maintains the highest value, which is beneficial for the improvement of corrosion resistance performance. With increasing the loading of GrF to


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3%, Rc does not display an increase due to the bad dispersion of GrF platelets in epoxy matrix (Figure 3g and 3h) although 3% GrF/epoxy coating with lower water absorption. And the hydrophobicity coating surface influenced by the dispersion state of GrF platelets also have a positive effect on the corrosion behavior. To further study the influence of coatings on the underlying steel surface, SEM analysis were conducted on the steel surface after the coatings were peeled off for 20 days of exposure to 3.5% NaCl solution. As observed in Figure S1, the carbon steel before corrosion exhibits obvious scratches because of rubbing the surface with sandpaper (Figure S1a). However, the steel surface after 20 days of immersion in 3.5% NaCl solution displays invisible polishing grooves and abundant accumulation of corrosion products with severe cracks (Figure S1b). In case of neat epoxy and 0.5% and 3% GrF/epoxy coatings, the steel surface also shows minimal accumulation of corrosion products when coatings were peeled off after 20 days of exposure to saline environment. In contrast, no obvious corrosion region is found in terms of steel covered by 1% GrF/epoxy coating. The visual observations shown in Figure S1 are complementary to EIS results shown in Figure 7 and Figure 8. Generally, for the coated steel substrate surfaces, electroactive species need to penetrate through the coating and then reach the steel surface for corrosion to take place. Consequently, the mechanism responsible for the improved corrosion resistance of 1% GrF platelets in this study can be ascribed to the following three reasons: (1) the introduction of GrF platelets is able to further improve the physical barrier performance of epoxy by providing a tortuous path for preventing water, oxygen and electrolyte penetrating through the coating, (2) the addition of superhydrophobic GrF platelets into epoxy can repel water, moisture and corrosive media adoption on the composites coating surface, preventing the underlying steel substrate from corrosion damage, (3) unlike conductive graphene, the GrF platelets are electrical insulating


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materials due to the covalence of C-F bond 48, which enable the GrF/epoxy coatings to insulate the cathodic and anodic sites on the steel substrate surface. Consequently, the corrosive species diffusion into the steel surface and the electron transfer from the anodic sites to cathodic regions can be remarkably restricted, resulting in the decrease of the steel corrosion rate.

Figure 8. The fitting results of the collected EIS results of different coatings. The inserted image is the equivalent electric circuits for fitting analysis.

3.3 Scratch resistance performance of GrF/epoxy coatings on steel substrate. In order to investigate whether the composites coating is capable of protecting the metal from crack attacking, the nanoscratch measurement has been carried out to describe the effective penetration scratch depth. Figure 9 shows the plot of the effective penetration scratch depth during the scratch process (lower curve in both plots) and the residual depth after scratch (upper curve in both plots) vs. the scratch distance for different coating on steel substrate. It can be observed that the effective penetration scratch depth of all the coatings experiences a linear increase with increasing the scratch distance during the scratch process, and the final scratch


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depth in the lower curve are almost the same. It should be noted here, there is no obvious sharp drop for the scratch depth during the scratch process, which is usually happened in quite brittle martials, like glass 35, 49. In terms of the residual depth after scratch described in the upper curve, the final scratch depth of 1% GrF/epoxy is much lower than that of other coatings, which indicates that our coating has better elastic recovery and less deformation. The enhanced scratch resistance of 1% GrF/epoxy can be attributed to the uniform dispersion of GrF platelets and the improved storage modulus and mechanical performance of composites35. What’s more, it can be clearly observed that the curve of 3% GrF/epoxy coating in Figure 9 is much rough and uneven, indicating large GrF aggregations embedded in the epoxy matrix leading to the high surface roughness of coating surface (Figure S2). It has been previously demonstrated that a relatively higher surface roughness (Ra) typically is corresponding to a lower surface friction coefficient, leading to the high scratch resistance for polymers coating 39, 50. Although 3% GrF/epoxy has higher surface roughness than that of 1% GrF/epoxy composites, the scratch resistant performance is still poorer than 1% GrF/epoxy due to the inferior mechanical performance.


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Figure 9. The plot of the effective penetration scratch depth during the scratch process (lower curve in both plots) and the residual depth after scratch (upper curve in both plots) vs. the scratch distance for different coating on steel substrate. (a) epoxy, (b) 0.5%, (c) 1%, (d) 3% GrF/epoxy.

To future investigate the scratch-resistant properties of our composite coatings, the elastic and plastic deformation as a function of GrF concentration obtained from nanoscratch test is described in Figure 10a. The elastic deformation of the neat epoxy coating is about 62%, while this value in composites coating with 0.5%, 1%, 3% GrF platelets is about 64%, 80%, 63%, respectively. The addition of 1% GrF endows a 29% increase in elastic deformation compared to the neat epoxy. The improvement of elastic deformation signifies that the incorporation of GrF in epoxy coating alters its elastic-plastic behavior via enhancing the portion related to the elastic work. Moreover, the highest elastic recovery in 1% GrF/epoxy is also reflected on the lowest residual scratch depth (upper curve) indicated in Figure 9. The increasing elastic recovery can


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also be ascribed to the uniform dispersion of GrF, the enhanced storage modulus and mechanical performance of composites. The pile-ups and residual depths are also the significant criteria that can be applied for investigating the mechanism occurred in the nanoscratch performance of composites 2, 51. The cross-profile topography of the neat epoxy and GrF/epoxy composites after the nanoscratch experiments is shown in Figure 10b. As observed, the height of pile-ups for composites coating are similar to the neat epoxy coating. Nevertheless, the depth of residual grooves in the neat coating is about 288 nm while this value in composites coating with 0.5, 1 and 3% GrF platelets is 174, 165 and 211 nm, respectively. The residual depth is reduced by 43% with the addition of 1% GrF into epoxy coating. It can be speculated that the addition of GrF platelets improve its elastic behavior and stiffness through hindering the mobility of epoxy chains, which correlates well with the DMA results shown in Figure 4a. Similar results have been observed in other research work on epoxy/MWNT 52 and epoxy/graphene 51 composites, as well. It can be found that the introduction of high scratch resistance composite coating is effectively preventing the steel substrate from crack attacking and is able to prolong the lifetime service of coatings. Given that scratch damage is usually encountered in most of the coating applications, such as highperformance packaging materials, lightweight vehicles, metal protections, aerospace structures etc., the excellent scratch resistance performance of our composite coatings demonstrated in our study would find extensive applications with high reliability.


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Figure 10. (a) The elastic and plastic deformation as a function of GrF concentration obtained from nanoscratch test. (b) The cross-profile topography of the neat epoxy and GrF/epoxy composites after the nanoscratch experiments.

By summarizing all the above studies, it is suggested that the introduction of 1% GrF platelets to epoxy can simultaneously improve the anti-corrosion and anti-scratch performance of the composites coating on steel substrate, which makes it very promising for the practical uses. As compared with conductive graphene/graphite platelets that are widely used in the corrosion protection applications 53-55, GrF owns much higher hydrophobicity and electric insulation performance, making it more suitable for corrosion-inhibiting coatings. The hydrophobicity provided by GrF is able to repel water and corrosive media diffusions into the steel surface while its favorable electrical insulation prevents the electron transfer from the anodic sites to cathodic regions. As a result, the corrosion resistance performance can be significantly improved. Meanwhile, the advanced scratch resistance, resulted from the uniform dispersion of GrF platelets and the increased storage modulus, can further extend the lifetime service for the coatings used in the corrosion protection applications. The multifunctional polymer coatings containing GrF are of great potential for metal protections of various harsh circumstances such as


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oil and gas pipelines, marine antifouling, architectural coatings, etc. Furthermore, GrF has a layered structure and is easy to be exfoliated into thinner nanosheets or even single-layered fluorographene 56-58. Therefore, it’s expected that the superhydrophobic fluorographene derived from the exfoliation of graphite fluoride in polymers would have greater potential uses as high performance multi-functional coatings.

4. CONCLUSIONS The current research offers a facile, solventless and surfactant-free method to prepare the advanced multi-functional GrF/epoxy coating with high anti-corrosion and anti-scratch performance. Good dispersion of GrF platelets in epoxy coating at low loading can be achieved without decreasing Tg of composites. The incorporation of 1% GrF into epoxy possesses the optimal properties, which showing excellent hydrophobicity, transparency, corrosion protection and scratch resistance performance. The coating resistance (Rc) exhibits a two orders of magnitude increase compared with that of the neat epoxy coating. The enhancement mechanism responsible for corrosion resistance can be ascribed to the following two factors: (1) the introduction of superhydrophobic GrF platelets prevents water, oxygen and electrolyte penetrating through the coating by providing a tortuous path, (2) the hydrophobic coating surface further repel water, moisture and corrosive media to approach the steel substrate, (3) the electron transfer from the anodic sites to cathodic regions can be remarkably restricted due to the excellent electrical insulating performance. Furthermore, the addition of 1% GrF endows a 29% increase in elastic deformation and 43% decrease in residual depth compared to the neat epoxy. It can be attributed to the uniform dispersion of GrF platelets and the improved storage modulus, thus prolonging the lifetime service of coating used in the corrosion protection applications. In


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addition, the preparation of GrF/epoxy multi-functional coating is economically attractive and environmentally friendly, which is able to be potentially applied in the large-scale commercial applications in enhancing the corrosion protection of metals.

ASSOCIATED CONTENT The supporting information is available free of charge on the ACS Publications website. Further details of SEM images of the samples before and after corrosion, and surface roughness of neat epoxy and composites coating can be found in the supporting information.

AUTHOR INFORMATION Corresponding Author *E-mail: [email protected] (Dazhi Sun) Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Notes The authors declare no competing financial interest. ACKNOWLEDGMENT This work was supported by the start-up funding from Southern University of Science and Technology (SUSTech), “The Recruitment Program of Global Youth Experts of China”, and the Foundation of Shenzhen Science and Technology Innovation Committee (Grant No.:


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JCYJ20170817110440310, KQJSCX20170726145415637, and JCYJ20160315164631204). Bingyu Wu acknowledges the “Innovation and Entrepreneurship Training Funding for Undergraduates” from SUSTech.

REFERENCES (1) Hand, R. J.; Ellis, B.; Whittle, B. R.; Wang, F. H. Epoxy based coatings on glass: strengthening mechanisms. J. Non-Cryst. Solids 2003, 315 (3), 276-287. (2) Lei, F.; Hamdi, M.; Liu, P.; Li, P.; Mullins, M.; Wang, H.; Li, J.; Krishnamoorti, R.; Guo, S.; Sue, H. J. Scratch behavior of epoxy coating containing self-assembled zirconium phosphate smectic layers. Polymer 2017, 112, 252-263. (3) Li, P.; He, X.; Huang, T. C.; White, K.; Zhang, X.; Liang, H.; Nishimura, R.; Sue, H. J. Highly effective anti-corrosion epoxy spray coatings containing self-assembled clay in smectic order. J. Mater. Chem. 2015, 3 (6), 2669-2676. (4) Chen, C.; Qiu, S.; Cui, M.; Qin, S.; Yan, G.; Zhao, H.; Wang, L.; Xue, Q. Achieving high performance corrosion and wear resistant epoxy coatings via incorporation of noncovalent functionalized graphene. Carbon 2017, 114, 356-366. (5) Behzadnasab, M.; Mirabedini, S. M.; Esfandeh, M. Corrosion protection of steel by epoxy nanocomposite coatings containing various combinations of clay and nanoparticulate zirconia. Corros. Sci. 2013, 75 (7), 134-141. (6) Sari, M. G.; Ramezanzadeh, B.; Shahbazi, M.; Pakdel, A. S. Influence of nanoclay particles modification by polyester-amide hyperbranched polymer on the corrosion protective performance of the epoxy nanocomposite. Corros. Sci. 2015, 92, 162-172.


25


Page 26 of 33

(7) Park, Y. T.; Qian, Y.; Chan, C.; Suh, T.; Nejhad, M. G.; Macosko, C. W.; Stein, A. Epoxy Toughening with Low Graphene Loading. Adv. Funct. Mater. 2015, 25 (4), 575-585. (8) Liu, W.; Hoa, S. V.; Pugh, M. Fracture toughness and water uptake of high-performance epoxy/nanoclay nanocomposites. Compos. Sci. Technol. 2005, 65 (15), 2364-2373. (9) Wong, M.; Ishige, R.; White, K. L.; Li, P.; Kim, D.; Krishnamoorti, R.; Gunther, R.; Higuchi, T.; Jinnai, H.; Takahara, A. Large-scale self-assembled zirconium phosphate smectic layers via a simple spray-coating process. Nat Commun. 2014, 5 (4). (10) Hu, Z.; Zhang, D.; Lu, F.; Yuan, W.; Xu, X.; Zhang, Q.; Liu, H.; Shao, Q.; Guo, Z.; Huang, Y. Multistimuli-responsive intrinsic self-healing epoxy resin constructed by host–guest interactions. Macromolecules 2018, 51 (14), 5294-5303. (11) Wu, Z.; Gao, S.; Chen, L.; Jiang, D.; Shao, Q.; Zhang, B.; Zhai, Z.; Wang, C.; Zhao, M.; Ma, Y. Electrically insulated epoxy nanocomposites reinforced with synergistic core–shell SiO2@ MWCNTs and montmorillonite bifillers. Macromol. Chem. Phys. 2017, 218 (23), 1700357. (12) Zhao, J.; Wu, L.; Zhan, C.; Shao, Q.; Guo, Z.; Zhang, L. Overview of polymer nanocomposites: Computer simulation understanding of physical properties. Polymer 2017. 133, 272-287 (13) Wang, C.; Zhao, M.; Li, J.; Yu, J.; Sun, S.; Ge, S.; Guo, X.; Xie, F.; Jiang, B.; Wujcik, E. K. Silver nanoparticles/graphene oxide decorated carbon fiber synergistic reinforcement in epoxy-based composites. Polymer 2017, 131, 263-271. (14) Rafiee, M. A.; Rafiee, J.; Wang, Z.; Song, H.; Yu, Z.-Z.; Koratkar, N. Enhanced mechanical properties of nanocomposites at low graphene content. ACS nano 2009, 3 (12), 3884-3890.


26

Page 27 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(15) Sue, H. J.; Gam, K. T.; Bestaoui, N.; N. Spurr, A.; Clearfield, A. Epoxy Nanocomposites Based on the Synthetic α-Zirconium Phosphate Layer Structure. Chem. Mater., 2004, 16 (2), 242–249. (16) Song, B.; Wang, T.; Wang, L.; Liu, H.; Mai, X.; Wang, X.; Wang, N.; Huang, Y.; Ma, Y.; Lu, Y. Interfacially reinforced carbon fiber/epoxy composite laminates via in-situ synthesized graphitic carbon nitride (g-C3N4). Compos. Part B, 2018. (17) Song, B.; Wang, T.; Sun, H.; Liu, H.; Mai, X.; Wang, X.; Wang, L.; Wang, N.; Huang, Y.; Guo, Z. Graphitic carbon nitride (g-C3N4) interfacially strengthened carbon fiber epoxy composites. Compos. Sci. Technol. 2018, 167, 515-521. (18) Chang, C. H.; Hsu, M. H.; Weng, C. J.; Hung, W.; Chuang, T. L.; Chang, K. C.; Peng, C. W.; Yen, Y. C.; Yeh, J. M. 3D-bioprinting approach to fabricate superhydrophobic epoxy/organophilic clay as an advanced anticorrosive coating with the synergistic effect of superhydrophobicity and gas barrier properties. J. Mater. Chem. 2013, 1 (44), 13869-13877. (19) Triantafyllidis, K. S.; LeBaron, P. C.; Park, I.; Pinnavaia, T. J. Epoxy− clay fabric film composites with unprecedented oxygen-barrier properties. Chem. Mater. 2006, 18 (18), 43934398. (20) Luo, J.; Yang, S.; Lei, L.; Zhao, J.; Tong, Z. Toughening, synergistic fire retardation and water resistance of polydimethylsiloxane grafted graphene oxide to epoxy nanocomposites with trace phosphorus. Compos. Part A, 2017, 100. 275-284. (21) Raimondo, M.; Guadagno, L.; Speranza, V.; Bonnaud, L.; Dubois, P.; Lafdi, K. Multifunctional graphene/POSS epoxy resin tailored for aircraft lightning strike protection. Compos. Part B, 2018, 140, 44-56.


27


Page 28 of 33

(22) Su, Z.; Wang, H.; Tian, K.; Huang, W.; Guo, Y.; He, J.; Tian, X. Multifunctional Anisotropic Flexible Cycloaliphatic Epoxy Resin Nanocomposites Reinforced by Aligned Graphite Flake with Non-covalent Biomimetic Functionalization. Compos. Part A, 2018. 109. 472-480. (23) Kang, H.; Cheng, Z.; Lai, H.; Ma, H.; Liu, Y.; Mai, X.; Wang, Y.; Shao, Q.; Xiang, L.; Guo, X. Superlyophobic anti-corrosive and self-cleaning titania robust mesh membrane with enhanced oil/water separation. Sep. Purif. Technol. 2018, 201, 193-204. (24) Yu, Y. H.; Lin, Y. Y.; Lin, C. H.; Chan, C. C.; Huang, Y. C. High-performance polystyrene/graphene-based nanocomposites with excellent anti-corrosion properties. Poly. Chem. 2013, 5 (2), 535-550. (25) Li, Y.; Yang, Z.; Qiu, H.; Dai, Y.; Zheng, Q.; Li, J.; Yang, J. Self-aligned graphene as anticorrosive barrier in waterborne polyurethane composite coatings. J. Mater. Chem. 2014, 2 (34), 14139-14145. (26) Chang, C. H.; Huang, T. C.; Peng, C. W.; Yeh, T. C.; Lu, H. I.; Hung, W. I.; Weng, C. J.; Yang, T. I.; Yeh, J. M. Novel anticorrosion coatings prepared from polyaniline/graphene composites. Carbon 2012, 50 (14), 5044-5051. (27) Chang, K.-C.; Hsu, M.-H.; Lu, H.-I.; Lai, M.-C.; Liu, P.-J.; Hsu, C.-H.; Ji, W.-F.; Chuang, T.-L.; Wei, Y.; Yeh, J.-M. Room-temperature cured hydrophobic epoxy/graphene composites as corrosion inhibitor for cold-rolled steel. Carbon 2015, 82 (2), 611-611. (28) Pourhashem, S.; Vaezi, M. R.; Rashidi, A.; Bagherzadeh, M. R. Exploring corrosion protection properties of solvent based epoxy-graphene oxide nanocomposite coatings on mild steel. Corros. Sci. 2016, 115, 78-92.


28

Page 29 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(29) Yao, H.; Hawkins, S. A.; Sue, H. J. Preparation of epoxy nanocomposites containing welldispersed graphene nanosheets. Compos. Sci. Technol. 2017, 146. 161-168. (30) Liu, W.; Hoa, S. V.; Pugh, M. Organoclay-modified high performance epoxy nanocomposites. Compos. Sci. Technol. 2005, 65 (2), 307-316. (31) Fusaro, R. L.; Sliney, H. E. Graphite Fluoride (CFx)n—A New Solid Lubricant. Tribol. Trans. 1970, 13 (1), 56-65. (32) Allam, I. M. Solid lubricants for applications at elevated temperatures. J. Mater. SCI. 1991, 26 (15), 3977-3984. (33) Lazar, P.; Otyepková, E.; Karlický, F.; Čépe, K.; Otyepka, M. The surface and structural properties of graphite fluoride. Carbon 2015, 94, 804-809. (34) Sun, H.; Jiang, F.; Chen, L.; Zhang, H.; Leng, J.; Sun, D. Graphite Fluoride Reinforced PA6 Composites: Crystallization and Mechanical Properties. Materials Today Communications 2018.16. 217-225. (35) Lei, F.; Zhang, C.; Cai, Z.; Yang, J.; Sun, H.; Sun, D. Epoxy toughening with graphite fluoride: Toward high toughness and strength. Polymer 2018, 150, 44-51. (36) Yang, Z.; Sun, W.; Wang, L.; Li, S.; Zhu, T.; Liu, G. Liquid-phase exfoliated fluorographene as a two dimensional coating filler for enhanced corrosion protection performance. Corros. Sci. 2016, 103, 312-318. (37) Yang, Z.; Wang, L.; Sun, W.; Li, S.; Zhu, T.; Liu, W.; Liu, G. Superhydrophobic epoxy coating modified by fluorographene used for anti-corrosion and self-cleaning. Appl. Surf. Sci. 2017, 401. 146-155.


29


Page 30 of 33

(38) Zhang, Y.; Zhao, M.; Zhang, J.; Shao, Q.; Li, J.; Li, H.; Lin, B.; Yu, M.; Chen, S.; Guo, Z. Excellent corrosion protection performance of epoxy composite coatings filled with silane functionalized silicon nitride. J. Polym. Res. 2018, 25 (5), 130. (39) Lei, F.; Yang, J.; Wu, B.; Chen, L.; Sun, H.; Zhang, H.; Sun, D. Facile design and fabrication of highly transparent and hydrophobic coatings on glass with anti-scratch property via surface dewetting. Prog. Org. Coat. 2018, 120, 28-35. (40) L, F.; E, M.; M, J.; A, H. Hard and flexible nanocomposite coatings using nanoclay-filled hyperbranched polymers. Acs Appl Mater Interfaces 2010, 2 (6), 1679-1684. (41) Ayatollahi, M. R.; Doagou‐Rad, S.; Shadlou, S. Nano‐/Microscale Investigation of Tribological and Mechanical Properties of Epoxy/MWNT Nanocomposites. Macromol. Mater. Eng. 2012, 297 (7), 689-701. (42) Fusaro, R. L.; Sliney, H. E. Graphite fluoride as a solid lubricant in a polyimide binder. 1972. Technical Report Washington, United States. (43) Zhang, H.; Chen, L.; Han, X.; Jiang, F.; Sun, H.; Sun, D. Enhanced mechanical properties of Nylon6 nanocomposites containing pristine α-zirconium phosphate nanoplatelets of various sizes by melt-compounding. RSC Adv. 2017, 7 (52), 32682-32691. (44) Zaman, I.; Phan, T. T.; Kuan, H.-C.; Meng, Q.; La, L. T. B.; Luong, L.; Youssf, O.; Ma, J. Epoxy/graphene platelets nanocomposites with two levels of interface strength. Polymer 2011, 52 (7), 1603-1611. (45) Zhang, P.; Zhao, J.; Zhang, K.; Bai, R.; Wang, Y.; Hua, C.; Wu, Y.; Liu, X.; Xu, H.; Li, Y. Fluorographene/polyimide composite films: Mechanical, electrical, hydrophobic, thermal and low dielectric properties. Compos. Part A. 2016, 84, 428-434.


30

Page 31 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(46) Chen, J. T.; Fu, Y. J.; An, Q. F.; Lo, S. C.; Zhong, Y. Z.; Hu, C. C.; Lee, K. R.; Lai, J. Y. Enhancing polymer/graphene oxide gas barrier film properties by introducing new crystals. Carbon 2014, 75 (8), 443-451. (47) Xia, W.; Xue, H.; Wang, J.; Wang, T.; Song, L.; Guo, H.; Fan, X.; Gong, H.; He, J. Functionlized graphene serving as free radical scavenger and corrosion protection in gammairradiated epoxy composites. Carbon 2016, 101, 315-323. (48) Yin, X.; Li, Y.; Feng, Y.; Feng, W. Polythiophene/graphite fluoride composites cathode for high power and energy densities lithium primary batteries. Synth. Met. 2016, 220, 560-566. (49) Crombez, R.; McMinis, J.; Veerasamy, V.; Shen, W. Experimental study of mechanical properties and scratch resistance of ultra-thin diamond-like-carbon (DLC) coatings deposited on glass. Tribol. Int. 2011, 44 (1), 55-62. (50) Jiang, H.; Browning, R.; Fincher, J.; Gasbarro, A.; Jones, S.; Sue, H.-J. Influence of surface roughness and contact load on friction coefficient and scratch behavior of thermoplastic olefins. Appl. Surf. Sci. 2008, 254 (15), 4494-4499. (51) Shokrieh, M. M.; Hosseinkhani, M. R.; Naimi-Jamal, M. R.; Tourani, H. Nanoindentation and nanoscratch investigations on graphene-based nanocomposites. Poly. Test. 2013, 32 (1), 4551. (52) Ayatollahi, M. R.; Doagou, Rad, S.; Shadlou, S. Nano/microscale investigation of tribological and mechanical properties of epoxy/mwnt nanocomposites. Macromol. Mater. Eng. 2012, 297 (7), 689-701. (53) Prasai, D.; Tuberquia, J. C.; Harl, R. R.; Jennings, G. K.; Rogers, B. R.; Bolotin, K. I. Graphene: corrosion-inhibiting coating. Acs Nano 2012, 6 (2), 1102-8.


31


Page 32 of 33

(54) Hsieh, Y. P.; Hofmann, M.; Chang, K. W.; Jian, G. J.; Li, Y. Y.; Chen, K. Y.; Yang, C. C.; Chang, W. S.; Chen, L. C. Complete Corrosion Inhibition through Graphene Defect Passivation. Acs Nano 2014, 8 (1), 443. (55) Raman, R. K. S.; Banerjee, P. C.; Lobo, D. E.; Gullapalli, H.; Sumandasa, M.; Kumar, A.; Choudhary, L.; Tkacz, R.; Ajayan, P. M.; Majumder, M. Protecting copper from electrochemical degradation by graphene coating. Carbon 2012, 50 (11), 4040-4045. (56) Zhang, M.; Ma, Y.; Zhu, Y.; Che, J.; Xiao, Y. Two-dimensional transparent hydrophobic coating based on liquid-phase exfoliated graphene fluoride. Carbon 2013, 63, 149-156. (57) Herraiz, M.; Dubois, M.; Batisse, N.; Hajjar, S.; Simon, L. Large-scale synthesis of fluorinated graphene by rapid thermal exfoliation of highly fluorinated graphite. Dalton Trans. 2018, 47(13), 4596-4606. (58) Yang, Y.; Lu, G.; Li, Y.; Liu, Z.; Huang, X. One-step preparation of fluorographene: a highly efficient, low-cost, and large-scale approach of exfoliating fluorographite. Acs Appl Mater Interfaces. 2013, 5 (24), 13478-13483.


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TOC

The hydrophobic coating surface is beneficial for the corrosion resistance improvement.


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Simultaneously Improving the Anticorrosion and Antiscratch

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