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One-step fabrication of superhydrophobic surface on beryllium copper alloys and corrosion protection application
Colloids and Surfaces A 556 (2018) 291–298
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Colloids and Surfaces A journal homepage: www.elsevier.com/locate/colsurfa
One-step fabrication of superhydrophobic surface on beryllium copper alloys and corrosion protection application Han Wanga,b, Shuliang Donga,b, Zhenlong Wanga,b, a b
T
⁎
Key Laboratory of Micro-systems and Micro-structures Manufacturing of Ministry of Education, Harbin Institute of Technology, Harbin 150001, Heilongjiang, China School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001, Heilongjiang, China
G R A P H I C A L A B S T R A C T
A R T I C LE I N FO
A B S T R A C T
Keywords: Superhydrophobic Electrodeposition Beryllium copper alloy Corrosion resistance Self-cleaning
Superhydrophobic surfaces have a wide application prospect in the future industrial production due to its special abilities. The fabrication of superhydrophobic coating on metal surfaces can improve its performance. A one-step electrodeposition method is proposed to construct nanostructures on the surface of beryllium copper (Be-Cu) alloys, and a mixture of copper chloride and stearic acid is used as the electrolytes. The static contact angle of water on the surface can reach up to 163 ± 4°, a sliding angle of 1.7 ± 0.2°. The nanostructure and chemical composition on the surface were evaluated by scanning electron microscopy and X-ray photoelectron spectroscopy respectively. The corrosion resistance was tested through electrochemical measurement. It was found that the as-prepared superhydrophobic coating improved the corrosion resistance significantly. In addition, the coating with excellent self-cleaning performance was proved. This method solves the problems of complicated process, improves the efficiency effectively, and the electrolyte is eco-friendly.
1. Introduction At present, the fabrication of superhydrophobic structure on the metal surfaces is a very hot research direction [1,2]. Superhydrophobic surfaces have expansive prospects applying to the industrial production
fields due to their special functions, such as self-cleaning, drag reduction, and corrosion protection [3–8]. Performance of equipment in industrial production can be significantly improved by using these properties [9–12]. Through experimental research, it has been found there are two major factors that determine the wettability of the
⁎ Corresponding author at: Key Laboratory of Micro-systems and Micro-structures Manufacturing of Ministry of Education, Harbin Institute of Technology, Harbin, 150001, Heilongjiang, China. E-mail address: [email protected] (Z. Wang).
https://doi.org/10.1016/j.colsurfa.2018.08.044 Received 13 June 2018; Received in revised form 13 August 2018; Accepted 16 August 2018 Available online 18 August 2018 0927-7757/ © 2018 Elsevier B.V. All rights reserved.
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Fig. 1. Schematic illustration of the main operational processes for one-step electrodeposition to fabricate superhydrophobic surface.
operation, eliminating the trouble of complicated multi-step process and reducing the risk of mis-operation effectively. The superhydrophobic coating can be changed by electrodeposition parameters adjustment according to different process requirements. The process is easy to control [15,36], and the superhydrophobic coating can be achieved within a few minutes. And its anti-corrosion capacity of the asprepared superhydrophobic surfaces was evaluated by electrochemical measurement, the results show that the corrosion resistance of the superhydrophobic surface is much higher than the ordinary surface. Broadly applied in aerospace and electronic, the superhydrophobic coating improves the performance of Be-Cu alloy products owe to corrosion resistance enhancement and self-cleaning performance. This method provides an idea for large-scale fabrication of superhydrophobic coating on Be-Cu alloy surface in industrial production due to the efficiency improvement, reducing the mis-operation effectively, simple in equipment low cost and environmentally friendly.
surface, they are the rough structure and the surface energy [13–15]. Based on these two factors, we should carry out superhydrophobic surface by fabricating a rough surface with micro-nanostructures and modifying the surface with low surface energy material simultaneously [16–18]. Be-Cu alloy has a very wide range of applications in the fields of aerospace, electromechanical products and communications equipment because of its good wear resistance, good electrical conductivity, good thermal conductivity and anti-interference of electromagnetic [19–21]. Due to the wide application of this alloy material, enhancing its corrosion resistance is very necessary. The superhydrophobic surface has good corrosion resistance [22–24], so to fabricate superhydrophobic coating on the surface of Be-Cu alloy material can improve the performance of the products and enhance the durability of the equipment. Up to now, there have been many studies on the fabrication of superhydrophobic surfaces by a variety of methods, including electrospinning [25], femtosecond laser technique [26–29], hydrothermal synthesis [30], self-assembly techniques [31], layer-by-layer deposition [17], chemical etching [32], and electrochemical process [33]. These methods are studied on the surface of glass, polymer [10], and metal materials. Chemical etching and electrochemical are the common techniques for fabricating superhydrophobic coating on metal substrates. Chen used a one-step method to etch the surface of the aluminum foils with a mixture of hydrochloric acid and stearic acid for 75 min to fabricate superhydrophobic surfaces [34]; Cui immersed the iron substrates in dilute hydrochloric acid then deposited in platinum chloride, followed by annealing at 170℃ [35]; Liu prepared a mixed solution of cerium nitrate and myristic acid and deposited nanostructures on the surfaces of the magnesium alloy by electrochemical method [36]; Shih-Fu Ou used anodizing on the surface of the NiTi shape memory alloy, and then modified with fluoroalkyl-silane to low the surface energy [37]. Through the previous researches, it has been found that the process of fabricating superhydrophobic surface is complicated, and it is accompanied by the toxicity problem of chemical reagents, moreover the expensive condition of facilities and inefficient process need to be solved. Here, a non-toxic, non-polluting, one-step electrodeposition method was proposed to fabricate superhydrophobic coating on the surface of Be-Cu alloys. Be-Cu alloy substrates were used as a cathode to deposit copper. The solution mixed cupric chloride, hydrochloric acid, and stearic acid were used as the electrolyte. The method combined the advantages of electrodeposition and low surface energy modification with inexpensive and non-toxic stearic acid at one-step, simple in
2. Experiment 2.1. Materials and reagents The Be-Cu alloy sheets (C17200) with the thickness of 2 mm were used as the substrates. The reagents used in the study including copper dichloride (CuCl2∙6H2O), hydrochloric acid (HCl), stearic acid (CH3(CH2)16COOH), sodium chloride (NaCl), acetone (C3H6O), ethanol (C2H5OH). All the reagents were analytically pure and used without further purification. Deionized water was used in the whole experiment process. 2.2. Fabrication of superhydrophobic surfaces Fig. 1 shows the main experimental process. The Be-Cu alloy was cut into sheets with a size of 25 mm × 10 mm × 2 mm. Then the sheets were sequentially polished with silicon carbide paper from 180 to 2000 mesh, ultrasonic pre-cleaned in acetone for 10 min, washed with deionized water, and dried in atmosphere condition. Measuring 60 mg stearic acid into the beaker loaded with 50 ml water, the mixture was dissolved in a water bath at 80℃ for 30 min, 2 ml 0.1 M CuCl2 and 3 ml 1 M HCl were added into the heated mixture, stirred uniformly. Electrodeposition used a DC voltage at room temperature, a Be-Cu alloy sheet as a cathode, a graphite sheet as an anode, a distance between the two electrodes of 15 mm. The operation was carried at a voltage of 5 V for different times (2 min, 5 min, 10 min, 15 min, 20 min), then cleaned 292
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with ethanol, dried under airflow, finally heated at 130℃ for 5 min. An electrodeposition for 10 min without stearic acid in the electrolyte was carried out as comparative study for chemical composition.
the obtained coating increased in thickness, the nanostructures nonuniformly shrunk during heating, resulting in gullies and nonuniform nanostructure forming where stearic acid accumulating. The wettability of the electrodeposition coating surfaces was measured by a contact angle meter. With the deposition time increasing, the static contact angle changed as shown in the Fig. 3a, from the curve it can be concluded that the water contact angles are all greater than 150°. When the deposition time is 10 min, the maximum contact angle is 163 ± 4°. As the deposition time goes on increase, the contact angle began to decrease. The sliding angle varies counter to the contact angle with the minimum of 1.7 ± 0.2°. Combined with the surface morphologies by SEM, it can be found that complex nanostructure plays a key role in the water-repel of the surfaces. Fig. 3d shows the change of surface roughness at different electrodeposition time measured by laser confocal microscope. It can be seen from the curve that the roughness Ra of the bare substrate is 0.51 μm, polished by sandpaper. When the deposition time increases, the surface roughness increases, which is consistent with the surface morphologies of SEM. When the electrodeposition time reaches 20 min, the surface roughness Ra is 1.12 μm. These coatings made the surface roughness increase not so largely, it can meet the roughness requirements of non-cooperation area. Although the surface roughness increases after 20 min of electrodeposition, the contact angle decreased due to the excessive deposition time that causes the undesirable content and distribution change of stearic acid on the coating. The air film formed by nanostructures effectively prevents the liquid from permeating the surface. As shown in the Fig. 3b, the superhydrophobic surface inserted into the water formed the air film, while the bare substrate not. A large amount of air exists in the contact interface, resulting in an increase on the contact angle. As the air film exists, the phenomenon can be explained according to the Cassie-Baxter model [39], when the proportion of air becomes larger, the contact angle increased.
2.3. Characterization 2.3.1. Surface characterization The surface morphologies of the coating obtained on Be-Cu alloy sheets were observed by scanning electron microscope (SEM, Hitachi SU8000) at 10 kV, the 3D morphologies were characterized using a laser confocal microscope (OLS3000; Olympus, Japan) to evaluate the roughness of the coating surfaces, chemical composition of the as-prepared sample was characterized by energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). A contact angle meter system (JC2000C1; Shanghai Zhongchen Digital Technic Apparatus Co, Ltd. China) was used to measure contact angle and sliding angle in air at room temperature. And the water droplet of 5 μL was used in each test. The values of contact angle and roughness were obtained by average of five different areas. 2.3.2. Electrochemical experiments The corrosion resistance of the superhydrophobic coatings was examined by electrochemical tests [38], including potentiodynamic polarization curve (Tafel) and electrochemical impedance spectroscopy (EIS) in 3.5 wt% NaCl solution at room temperature on the electrochemical workstation (CHI660D, CH Instruments Inc.). A three-electrode system was used in the test: a saturated calomel electrode (Ag/ AgCl, 3 M KCl) was used as reference electrode, while the counter electrode and the working electrode severally used a graphite electrode and the as-prepared samples. The working area of the working electrode was 1 cm2. The scanning range of the Tafel curves was −0.05 V to −0.3 V, with scanning rate of 1 mV/s. The EIS tests were carried out from 105 to 1 Hz of the AC signal frequencies under open circuit potential with the amplitude of the perturbation voltage of 5 mV. The asprepared samples were immersed in the electrolyte for 20 min prior to electrochemical experiments, each test was repeated more than three times to verify the repeatability of the results.
3.2. Chemical composition The chemical composition of the surfaces was analyzed using energy dispersive X-ray spectroscopy (EDS). The coating electrodeposition for 10 min was measured and an electrolyte without stearic acid was used as a comparison. The EDS spectrums are shown in Fig. 4. Fig. 4a shows the result of the electrolyte containing stearic acid and Fig. 4b shows the result without stearic acid. The percentages of weight and atomicity of the coatings are shown in Table 1. Combined with the test results, it is found that the weight percentage of C element on the superhydrophobic surface is 6.13% and the number of atoms accounts for 24.12%. The surface without stearic acid doesn’t contain C element. Stearic acid plays a key role in the wettability of the coating to low surface energy. The O element of the superhydrophobic surface is mainly derived from stearic acid, while the O element weight percentage without stearic acid is 4.38%, and atomic percentage is 15.40%, higher than the superhydrophobic surface. It is because Cu electrodeposited on the surface is oxidized to form copper oxide. The study indicates that surface modified by low surface energy chemicals is not easily oxidized. X-ray photoelectron spectroscopy (XPS) was utilized to investigate the chemical composition of the superhydrophobic surface electrodeposition for 10 min. The results are shown in Fig. 5. Fig. 5a shows the survey spectrum of the superhydrophobic surface. The peaks of C, O and Cu element are indicated in the spectrum. It is found that a stearic acid layer has been linked on the superhydrophobic coating, which reduces the surface energy significantly. Fig. 5b is the high-resolution spectrum of C1s. The peaks of C element can be resolved into two components. The peak at 284.54 eV corresponds to methyl (eCH3) and methylene (eCH2), and the peak at 288.48 eV corresponds to carboxyl functional group (eCOOH) [34]. Comparing the peak areas, it implies that the peaks of methylene and methyl groups are significantly higher
3. Results and discussion 3.1. Surface morphology and wettability The microscopic morphologies of the surfaces were observed by SEM, as shown in Fig. 2, which shows the images of low-magnification and high-magnification surface morphologies obtained by one-step electrodeposition processing of different time. Fig. 2(c2) is a typical superhydrophobic surface nanostructure. As can be seen from the image, the structures exhibited a chain of particles, and they grew based on the surface. The enlarged view shows that the chain structure is small grainy crystals that piled up, and new chains were grown base on the branches, accumulated to form a layer nanostructure. Since the surface structure is a multimodal growth type, many tiny voids were generated, providing geometry conditions for forming superhydrophobic surfaces. Comparing the surface morphologies of different electrodeposition time, it is found that the original surface of the substrate can be observed at the deposition time of 2 min (shown in Fig. 2(a1)). The particle structures deposited were sparse, and the nanostructures on the surfaces were very nonuniform. With the deposition time increasing, the bare substrate was gradually covered by the cross-link chain structure, and the nanostructure on the surface tended to be uniform (shown in Fig. 2(b1)). As the deposition time increases continuously, the chains were more crossed, and the voids distribution became more uniform (shown in Fig. 2(c1)). When the deposition time exceeds 15 min (shown in Fig. 2(d1)), gullies appear on the coating, as can be seen in the Fig. 2(d2). Because the electrodeposition time is too long, 293
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Fig. 2. SEM images of electrodeposition coating on the Be-Cu alloy at different electrodeposition time (a1) 2 min (b1) 5 min (c1) 10 min (d1) 15 min (e1) 20 min, (a2)–(e2) are the accordingly magnification images, respectively.
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Fig. 4. EDS of the as-prepared surfaces. (a) electrodeposition for 10 min with stearic acid and (b) electrodeposition for 10 min without stearic acid.
Table 1 Summary of element composition in EDS research of the coating electrodeposition for 10 min with (a) / without (b) stearic acid. element
C O Cu
Fig. 3. (a) Variation in the water contact angle and sliding angle of the asprepared surfaces as function of electrodeposition time. (b) and (c) are the optical photographs of the coating electrodeposition for 10 min and the bare BeCu alloy substrate immersed in the water. (d) Variation in the roughness of the as-prepared surfaces as function of electrodeposition time.
with stearic acid
without stearic acid
weight/%
atomic/%
weight/%
atomic/%
6.13 2.71 91.16
24.12 8.02 67.86
– 4.38 95.62
– 15.40 84.60
processes on the cathode are as follows: Cu2+ + 2e− → Cu Cu2+ + 2CH3(CH2)16COOH →Cu [CH3(CH2)16COO]2 + 2H+
than those of carboxyl functional groups, which is corresponding to the molecular structure of stearic acid. Fig. 5c shows the high-resolution region of Cu2p. It can be seen that the two main peaks are 931.33 eV and 951.23 eV, corresponding to Cu2p3/2 and Cu2p1/2, respectively, representing the bonding mode of pure metallic copper, and there are two peaks at 943.51 eV and 961.34 eV, attributed to CueO coordination [13,40]. This means that O]Ce groups are bonded with Cu2+. From the aspect of the peak area ratio, CueO bonds are less, and the coating exists in the form of pure copper. In the mixed electrolyte, stearic acid is dissociated, and H+, CH3(CH2)16COO−, Cu2+ are present in the electrolyte and react under the electric field. The main reaction
2H+ + 2e− →H2 ↑
3.3. Corrosion resistance Metal surfaces would damage if contact liquid environment corrosive frequently, and improving the performance of the corrosion resistance of the metal is very necessary in engineering applications. For Be-Cu alloy, the service life of the product can be effectively enhanced when the corrosion resistance is improved. The superhydrophobic 295
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Fig. 6. Tafel curves of the bare Be-Cu alloy substrate, coatings electrodeposition for 10 min and 20 min in 3.5 wt% NaCl solution. Table 2 Electrochemical parameters from the Tafel curves of the bare Be-Cu alloy and surface coatings electrodeposited for different time. Sample
Ecorr(V)
icorr(A∙cm−2)
ηIE(%)
bare Be-Cu alloy electrodeposition for 10 min electrodeposition for 20 min
−1.20 × 10-1 −9.2 × 10-2 −9.1 × 10-2
2.609 × 10−4 3.710 × 10−5 6.309 × 10−5
– 85.8 75.8
ηIE =
i 0−icorr × 100% i0
(1)
Where i 0 and icorr are the current density of the bare Be-Cu alloy and the coatings respectively. In general, higher corrosion potential and lower corrosion current density represent for better corrosion resistance. The data shows that after electrodeposition, the surface was superhydrophobic, and the anticorrosion potential of the coating surface improved compared with the smooth surface, while the corrosion current density reduced. The thickness of the coating has a great influence on the corrosion current density [3,21]. The Ecorr of the bare Be-Cu alloy surface was −1.20 × 10−1 V, in contrast, the Ecorr of the surfaces electrodeposition for 10 min and 20 min were −9.2 × 10−2 V and −9.1 × 10−2 V correspondingly. The icorr of the bare surface was 2.609 × 10−4 A cm−2, the coating electrodeposition for 10 min was 3.710 × 10−5 A cm−2, electrodeposition for 20 min was 6.309 × 10−5 A cm−2, the corrosion current density of superhydrophobic surfaces reduced so much. As for ηIE , they were calculated that the electrodeposition for 10 min was 85.8%, electrodeposition for 20 min was 75.8%. The coating electrodeposition for 10 min performed the better corrosion resistance. Further research, EIS tests were carried out as the supplement of the Tafel curves to evaluate the anti-corrosion of the as-prepared superhydrophobic coatings. Fig. 7a is the Nyquist plot of the bare surface and the coatings. It can be found that the impedance semicircle diameter of the coating electrodeposition for 10 min is the largest, the bare Be-Cu alloy is the least, shown in the Nyquist plot, the largest impedance semicircle diameter was 25 times to the smallest one. It is known that the diameter represents the polarization resistance of the samples [36], the surface electrodeposition for 10 min performed the best anti-corrosion property. The Bode plot is shown in Fig. 7b, in the high-frequent part, |Z| of the three samples were much close, while in the low-frequent part, the |Z| of the coating electrodeposition for 10 min was up to 417 Ω cm2, 25 times of the bare surface. When electrodeposition for 20 min, the anticorrosion was lower than 10 min, because of the wettability of the coatings lower than electrodeposition for 10 min. The wetting of the coating surfaces is in accord with the Cassie-
Fig. 5. XPS of the as-prepared surface electrodeposition for 10 min. (a) survey spectrum, (b) C1s region, (c) Cu2p region.
coating can effectively improve the corrosion resistance of the material surface, so the use of this coating on the Be-Cu alloy products is significant. In order to test the corrosion resistance property of the asprepared coatings, the surface was subjected to electrochemical corrosion resistance analysis, the Tafel curves and EIS of the samples were measured in the 3.5 wt% NaCl solution at room temperature. The Tafel curves of the bare Be-Cu alloy and the surfaces electrodeposition for 10 min and 20 min are shown in the Fig. 6, some parameters related to the Tafel curves are listed in the Table 2 such as corrosion potential (Ecorr ), corrosion current density (icorr ) and the inhibition efficiency (ηIE), where ηIE can get by the formula [41]: 296
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Fig. 8. Self-cleaning performance evolution. (a) the as-prepared coating electrodeposition for 10 min, (b) the bare Be-Cu alloy substrate. (a2) and (b2) the substrates sloped by 5°, (a3) and (b3) the substrates laid flat and waterdrop added vertically.
Fig. 8a3 and b3. The superhydrophobic surface formed a sphere and the surrounding particles were rolled up, while the smooth surface droplets spread the surface. The results show that the as-prepared superhydrophobic surface has good self-cleaning property and can be used in practical pollution applications after verification. When water droplets flow through the coating surface, it can carry dust and escape from the surface together, which presents anti-fouling effect compared with the smooth substrate, the superhydrophobic surface has no water droplets remaining, reflecting the water resistance of the coating. Taking advantage of its non-wetting properties, the coating can be used in lossless liquid transport.
Fig. 7. EIS of the bare Be-Cu alloy substrate and coatings electrodeposition for 10 min and 20 min in 3.5 wt% NaCl solution. (a) the Nyquist plot, the inset is the magnification in the low impedance region, (b) the Bode plot (|Z| changes as the function of frequency ranging from 1 to 105 Hz).
Baxter case, that is related to heterogeneous wetting, there is air film between the liquid and the coating surface, where the coating has water repellent effect, so the real contact area between the electrolyte and surface nanostructure is very small. In the other hand, active corrosive sites are occupied by hydrophobic molecules, decreased the adsorption of corrosive ions on the surface effectively, which inhibits the corrosion reaction, at the same time, the hydrophobic molecular layer is a barrier for charge transfer, stearic acid chain inhibits charge transfer from coating to liquid [42,43]. In conclusion, superhydrophobic coating enhances the corrosion resistance of surface.
4. Conclusion In this paper, a method of one-step electrodeposition to fabricate superhydrophobic coating on the surface of C17200 substrates was proposed. Using an electrolyte mixture of heated stearic acid, hydrochloric acid, and cupric chloride, the Be-Cu alloy substrate acted as a cathode, forming a superhydrophobic coating on the surface. SEM, EDS and XPS tests were used to analyze the morphology and chemical composition of the surface. The effects of electrodeposition time of the superhydrophobic coating were studied. When the electrodeposition time was 10 min, the high static contact angle up to 163 ± 4° and sliding angle of 1.7 ± 0.2° was obtained. The corrosion resistance of superhydrophobic coatings can be improved by 25 times compared with bare Be-Cu alloy through electrochemical tested. The experiment results show that superhydrophobic surface has a good self-cleaning performance. In addition, this method is high fabrication efficiency by using electrodeposition method, and the working fluid is low-cost without pollution, solving the problem of complex process.
3.4. Self-cleaning property Self-cleaning is a property of superhydrophobic surface [15,44]. The fact that the lotus glowing beneath the dirt is an indication of the selfcleaning property of the super hydrophobic surface of the lotus leaf [13]. The self-cleaning property can be applied to many occasions such as anti-pollution and dustproof. Self-cleaning tests were performed on the as-prepared superhydrophobic surfaces. Fig. 8 shows an experimental comparison of a superhydrophobic coating with a smooth substrate, with quartz sand particles on the surfaces, as shown in Fig. 8a1 and b1. Sloped the substrates by 5°, and used a pipette to jet on the surface, as shown in Fig. 8a2 and b2. On the superhydrophobic surface, droplets carried the quartz sand particles off the surface, and the path of the droplets movement is shown in the photograph, while the droplets penetrated into particles on the smooth surface. Then the substrates laid flat and drops of water were dropped vertically, the results are shown in
Acknowledgement This work is supported by National Nature Science Foundation of China (Grant Nos. 51775145). 297
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References
[23] W. Xu, Y. Hu, W. Bao, X. Xie, Y. Liu, A. Song, J. Hao, Superhydrophobic copper surfaces fabricated by fatty acid soaps in aqueous solution for excellent corrosion resistance, Appl. Surf. Sci. 399 (2017) 491–498. [24] L.B. Boinovich, A.M. Emelyanenko, A.D. Modestov, A.G. Domantovsky, K.A. Emelyanenko, Synergistic effect of superhydrophobicity and oxidized layers on corrosion resistance of aluminum alloy surface textured by nanosecond laser treatment, ACS Appl. Mater. Interfaces 7 (2015) 19500–19508. [25] F. Yang, J.E. Efome, D. Rana, T. Matsuura, C. Lan, Metal–Organic frameworks supported on nanofiber for desalination by direct contact membrane distillation, ACS Appl. Mater. Interfaces 10 (2018) 11251–11260. [26] S. Ye, Q. Cao, Q. Wang, T. Wang, Q. Peng, A highly efficient, stable, durable, and recyclable filter fabricated by femtosecond laser drilling of a titanium foil for oilwater separation, Sci. Rep.-UK 6 (2016). [27] C. Ngo, D. Chun, Fast wettability transition from hydrophilic to superhydrophobic laser-textured stainless steel surfaces under low-temperature annealing, Appl. Surf. Sci. 409 (2017) 232–240. [28] S. Sarbada, Y.C. Shin, Superhydrophobic contoured surfaces created on metal and polymer using a femtosecond laser, Appl. Surf. Sci. 405 (2017) 465–475. [29] J. Long, P. Fan, D. Gong, D. Jiang, H. Zhang, L. Li, M. Zhong, Superhydrophobic Surfaces Fabricated by Femtosecond Laser with Tunable Water Adhesion: From Lotus Leaf to Rose Petal, ACS Appl. Mater. Interfaces 7 (2015) 9858–9865. [30] H. Wang, Q. Yao, C. Wang, B. Fan, Q. Sun, C. Jin, Y. Xiong, Y. Chen, A simple, onestep hydrothermal approach to durable and robust superparamagnetic, superhydrophobic and electromagnetic wave-absorbing wood, Sci. Rep.-UK 6 (2016). [31] L. Jia, A. Petretic, G. Molev, G. Guerin, I. Manners, M.A. Winnik, Hierarchical polymer–carbon nanotube hybrid mesostructures by crystallization-driven self-assembly, ACS Nano 9 (2015) 10673–10685. [32] H.M. Forooshani, M. Aliofkhazraei, A.S. Rouhaghdam, Superhydrophobic aluminum surfaces by mechanical/chemical combined method and its corrosion behavior, J. Taiwan Inst. Chem. E 72 (2017) 220–235. [33] H. Wang, Z. Hu, Y. Zhu, S. Yang, K. Jin, Y. Zhu, toward easily enlarged superhydrophobic materials with stain-resistant, oil–water separation and anticorrosion function by a water-based one-step electrodeposition method, Ind. Eng. Chem. Res. 56 (2017) 933–941. [34] C. Chen, S. Yang, L. Liu, H. Xie, H. Liu, L. Zhu, X. Xu, A green one-step fabrication of superhydrophobic metallic surfaces of aluminum and zinc, J. Alloy Compd. 711 (2017) 506–513. [35] S. Cui, S. Lu, W. Xu, B. Wu, Fabrication of superhydrophobic Pt 3 Fe/Fe surface for its application, J. Solid State Chem. 254 (2017) 14–24. [36] Y. Liu, J. Xue, D. Luo, H. Wang, X. Gong, Z. Han, L. Ren, One-step fabrication of biomimetic superhydrophobic surface by electrodeposition on magnesium alloy and its corrosion inhibition, J. Colloid Interface Sci. 491 (2017) 313–320. [37] S. Ou, K. Wang, Y. Hsu, Superhydrophobic NiTi shape memory alloy surfaces fabricated by anodization and surface mechanical attrition treatment, Appl. Surf. Sci. 425 (2017) 594–602. [38] H. Qian, M. Li, Z. Li, Y. Lou, L. Huang, D. Zhang, D. Xu, C. Du, L. Lu, J. Gao, Musselinspired superhydrophobic surfaces with enhanced corrosion resistance and dualaction antibacterial properties, Mater. Sci. Eng. C 80 (2017) 566–577. [39] A. Marmur, Wetting on hydrophobic rough surfaces: to be heterogeneous or not to be? Langmuir 19 (2003) 8343–8348. [40] W. Yang, J. Li, P. Zhou, L. Zhu, H. Tang, Superhydrophobic copper coating: Switchable wettability, on-demand oil-water separation, and antifouling, Chem. Eng. J. 327 (2017) 849–854. [41] S. Yuan, S.O. Pehkonen, B. Liang, Y.P. Ting, K.G. Neoh, E.T. Kang, Superhydrophobic fluoropolymer-modified copper surface via surface graft polymerisation for corrosion protection, Corros. Sci. 53 (2011) 2738–2747. [42] L.B. Boinovich, A.M. Emelyanenko, A.D. Modestov, A.G. Domantovsky, A.A. Shiryaev, K.A. Emelyanenko, O.V. Dvoretskaya, A.A. Ganne, Corrosion behavior of superhydrophobic aluminum alloy in concentrated potassium halide solutions: when the specific anion effect is manifested, Corros. Sci. 112 (2016) 517–527. [43] L.B. Boinovich, A.M. Emelyanenko, K.A. Emelyanenko, A.D. Modestov, A.G. Domantovsky, Not simply repel water: the diversified nature of corrosion protection by superhydrophobic coatings, Mendeleev Commun. 27 (2017) 254–256. [44] W. Sun, L. Wang, Z. Yang, S. Li, T. Wu, G. Liu, Fabrication of polydimethylsiloxanederived superhydrophobic surface on aluminium via chemical vapour deposition technique for corrosion protection, Corros. Sci. 128 (2017) 176–185.
[1] H. Yang, Y. He, Z. Wu, J. Miao, F. Yang, Z. Lu, Fabrication of a superhydrophobic and high-glossy copper coating on aluminum substrates, Appl. Surf. Sci. 433 (2018) 1192–1196. [2] E.J.Y. Ling, V. Uong, J. Renault-Crispo, A. Kietzig, P. Servio, Reducing ice adhesion on nonsmooth metallic surfaces: wettability and topography effects, ACS Appl. Mater. Interfaces 8 (2016) 8789–8800. [3] Y. Tuo, H. Zhang, W. Chen, X. Liu, Corrosion protection application of slippery liquid-infused porous surface based on aluminum foil, Appl. Surf. Sci. 423 (2017) 365–374. [4] E. Liu, L. Li, G. Wang, Z. Zeng, W. Zhao, Q. Xue, Drag reduction through selftexturing compliant bionic materials, Sci. Rep.-UK 7 (2017) 40038. [5] S. Bano, U. Zulfiqar, U. Zaheer, M. Awais, I. Ahmad, T. Subhani, Durable and recyclable superhydrophobic fabric and mesh for oil-water separation, Adv. Eng. Mater. 20 (2018) 1700460. [6] G. Wang, Z. Zeng, H. Wang, L. Zhang, X. Sun, Y. He, L. Li, X. Wu, T. Ren, Q. Xue, Low drag porous ship with superhydrophobic and superoleophilic surface for oil spills cleanup, ACS Appl. Mater. Interfaces 7 (2015) 26184–26194. [7] Z. Zhang, H. Wang, Y. Liang, X. Li, L. Ren, Z. Cui, C. Luo, One-step fabrication of robust superhydrophobic and superoleophilic surfaces with self-cleaning and oil/ water separation function, Sci. Rep.-UK 8 (2018). [8] Y. Qing, C. Hu, C. Yang, K. An, F. Tang, J. Tan, C. Liu, Rough structure of electrodeposition as a template for an ultrarobust self-cleaning surface, ACS Appl. Mater. Interfaces 9 (2017) 16571–16580. [9] E. Battista, M.L. Coluccio, A. Alabastri, M. Barberio, F. Causa, P.A. Netti, E. Di Fabrizio, F. Gentile, Metal enhanced fluorescence on super-hydrophobic clusters of gold nanoparticles, Microelectron. Eng. 175 (2017) 7–11. [10] L. Xiao, M. Deng, W. Zeng, B. Zhang, Z. Xu, C. Yi, G. Liao, Novel robust superhydrophobic coating with self-cleaning properties in air and oil based on rare earth metal oxide, Ind. Eng. Chem. Res. 56 (2017) 12354–12361. [11] J. Brassard, J. Laforte, C. Blackburn, J. Perron, D.K. Sarkar, Silicone based superhydrophobic coating efficient to reduce ice adhesion and accumulation on aluminum under offshore arctic conditions, Ocean Eng. 144 (2017) 135–141. [12] V. Jokinen, E. Kankuri, S. Hoshian, S. Franssila, R.H.A. Ras, Superhydrophobic blood-repellent surfaces, Adv. Mater. (2018) 1705104. [13] W. Jiang, M. Mao, W. Qiu, Y. Zhu, B. Liang, Biomimetic superhydrophobic engineering metal surface with hierarchical structure and tunable adhesion: design of microscale pattern, Ind. Eng. Chem. Res. 56 (2017) 907–919. [14] N. Karthik, T.N.J.I. Edison, Y.R. Lee, M.G. Sethuraman, Fabrication of corrosion resistant mussel-yarn like superhydrophobic composite coating on aluminum surface, J. Taiwan Inst. Chem. E 77 (2017) 302–310. [15] Z. Kang, W. Li, Facile and fast fabrication of superhydrophobic surface on magnesium alloy by one-step electrodeposition method, J. Ind. Eng. Chem. 50 (2017) 50–56. [16] L.B. Boinovich, E.B. Modin, A.R. Sayfutdinova, K.A. Emelyanenko, A.L. Vasiliev, A.M. Emelyanenko, Combination of functional nanoengineering and nanosecond laser texturing for design of superhydrophobic aluminum alloy with exceptional mechanical and chemical properties, ACS Nano 11 (2017) 10113–10123. [17] T. Xiang, Y. Han, Z. Guo, R. Wang, S. Zheng, S. Li, C. Li, X. Dai, Fabrication of inherent anticorrosion superhydrophobic surfaces on metals, ACS Sustain. Chem. Eng. 6 (2018) 5598–5606. [18] I. Vilaró, J.L. Yagüe, S. Borrós, Superhydrophobic Copper Surfaces with Anticorrosion Properties Fabricated by Solventless CVD Methods, ACS Appl. Mater. Interfaces 9 (2016) 1057–1065. [19] Y. Yildiz, M.M. Sundaram, K.P. Rajurkar, Empirical modeling of the white layer thickness formed in electrodischarge drilling of beryllium–copper alloys, Int. J. Adv. Manuf. Technol. 66 (2013) 1745–1755. [20] S. Dong, Z. Wang, Y. Wang, High-speed electrochemical discharge drilling (HSECDD) for micro-holes on C17200 beryllium copper alloy in deionized water, Int. J. Adv. Manuf. Technol. 88 (2017) 827–835. [21] S. Dong, Z. Wang, Y. Wang, X. Bai, Y.Q. Fu, B. Guo, C. Tan, J. Zhang, P. Hu, Roll-toRoll Manufacturing of Robust Superhydrophobic Coating on Metallic Engineering Materials, ACS Appl. Mater. Interfaces 10 (2018) 2174–2184. [22] Y. Cheng, S. Lu, W. Xu, R. Boukherroub, S. Szunerits, W. Liang, Controlled fabrication of NiO/ZnO superhydrophobic surface on zinc substrate with corrosion and abrasion resistance, J. Alloy. Compd. 723 (2017) 225–236.
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Contents lists available at ScienceDirect
Colloids and Surfaces A journal homepage: www.elsevier.com/locate/colsurfa
One-step fabrication of superhydrophobic surface on beryllium copper alloys and corrosion protection application Han Wanga,b, Shuliang Donga,b, Zhenlong Wanga,b, a b
T
⁎
Key Laboratory of Micro-systems and Micro-structures Manufacturing of Ministry of Education, Harbin Institute of Technology, Harbin 150001, Heilongjiang, China School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001, Heilongjiang, China
G R A P H I C A L A B S T R A C T
A R T I C LE I N FO
A B S T R A C T
Keywords: Superhydrophobic Electrodeposition Beryllium copper alloy Corrosion resistance Self-cleaning
Superhydrophobic surfaces have a wide application prospect in the future industrial production due to its special abilities. The fabrication of superhydrophobic coating on metal surfaces can improve its performance. A one-step electrodeposition method is proposed to construct nanostructures on the surface of beryllium copper (Be-Cu) alloys, and a mixture of copper chloride and stearic acid is used as the electrolytes. The static contact angle of water on the surface can reach up to 163 ± 4°, a sliding angle of 1.7 ± 0.2°. The nanostructure and chemical composition on the surface were evaluated by scanning electron microscopy and X-ray photoelectron spectroscopy respectively. The corrosion resistance was tested through electrochemical measurement. It was found that the as-prepared superhydrophobic coating improved the corrosion resistance significantly. In addition, the coating with excellent self-cleaning performance was proved. This method solves the problems of complicated process, improves the efficiency effectively, and the electrolyte is eco-friendly.
1. Introduction At present, the fabrication of superhydrophobic structure on the metal surfaces is a very hot research direction [1,2]. Superhydrophobic surfaces have expansive prospects applying to the industrial production
fields due to their special functions, such as self-cleaning, drag reduction, and corrosion protection [3–8]. Performance of equipment in industrial production can be significantly improved by using these properties [9–12]. Through experimental research, it has been found there are two major factors that determine the wettability of the
⁎ Corresponding author at: Key Laboratory of Micro-systems and Micro-structures Manufacturing of Ministry of Education, Harbin Institute of Technology, Harbin, 150001, Heilongjiang, China. E-mail address: [email protected] (Z. Wang).
https://doi.org/10.1016/j.colsurfa.2018.08.044 Received 13 June 2018; Received in revised form 13 August 2018; Accepted 16 August 2018 Available online 18 August 2018 0927-7757/ © 2018 Elsevier B.V. All rights reserved.
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Fig. 1. Schematic illustration of the main operational processes for one-step electrodeposition to fabricate superhydrophobic surface.
operation, eliminating the trouble of complicated multi-step process and reducing the risk of mis-operation effectively. The superhydrophobic coating can be changed by electrodeposition parameters adjustment according to different process requirements. The process is easy to control [15,36], and the superhydrophobic coating can be achieved within a few minutes. And its anti-corrosion capacity of the asprepared superhydrophobic surfaces was evaluated by electrochemical measurement, the results show that the corrosion resistance of the superhydrophobic surface is much higher than the ordinary surface. Broadly applied in aerospace and electronic, the superhydrophobic coating improves the performance of Be-Cu alloy products owe to corrosion resistance enhancement and self-cleaning performance. This method provides an idea for large-scale fabrication of superhydrophobic coating on Be-Cu alloy surface in industrial production due to the efficiency improvement, reducing the mis-operation effectively, simple in equipment low cost and environmentally friendly.
surface, they are the rough structure and the surface energy [13–15]. Based on these two factors, we should carry out superhydrophobic surface by fabricating a rough surface with micro-nanostructures and modifying the surface with low surface energy material simultaneously [16–18]. Be-Cu alloy has a very wide range of applications in the fields of aerospace, electromechanical products and communications equipment because of its good wear resistance, good electrical conductivity, good thermal conductivity and anti-interference of electromagnetic [19–21]. Due to the wide application of this alloy material, enhancing its corrosion resistance is very necessary. The superhydrophobic surface has good corrosion resistance [22–24], so to fabricate superhydrophobic coating on the surface of Be-Cu alloy material can improve the performance of the products and enhance the durability of the equipment. Up to now, there have been many studies on the fabrication of superhydrophobic surfaces by a variety of methods, including electrospinning [25], femtosecond laser technique [26–29], hydrothermal synthesis [30], self-assembly techniques [31], layer-by-layer deposition [17], chemical etching [32], and electrochemical process [33]. These methods are studied on the surface of glass, polymer [10], and metal materials. Chemical etching and electrochemical are the common techniques for fabricating superhydrophobic coating on metal substrates. Chen used a one-step method to etch the surface of the aluminum foils with a mixture of hydrochloric acid and stearic acid for 75 min to fabricate superhydrophobic surfaces [34]; Cui immersed the iron substrates in dilute hydrochloric acid then deposited in platinum chloride, followed by annealing at 170℃ [35]; Liu prepared a mixed solution of cerium nitrate and myristic acid and deposited nanostructures on the surfaces of the magnesium alloy by electrochemical method [36]; Shih-Fu Ou used anodizing on the surface of the NiTi shape memory alloy, and then modified with fluoroalkyl-silane to low the surface energy [37]. Through the previous researches, it has been found that the process of fabricating superhydrophobic surface is complicated, and it is accompanied by the toxicity problem of chemical reagents, moreover the expensive condition of facilities and inefficient process need to be solved. Here, a non-toxic, non-polluting, one-step electrodeposition method was proposed to fabricate superhydrophobic coating on the surface of Be-Cu alloys. Be-Cu alloy substrates were used as a cathode to deposit copper. The solution mixed cupric chloride, hydrochloric acid, and stearic acid were used as the electrolyte. The method combined the advantages of electrodeposition and low surface energy modification with inexpensive and non-toxic stearic acid at one-step, simple in
2. Experiment 2.1. Materials and reagents The Be-Cu alloy sheets (C17200) with the thickness of 2 mm were used as the substrates. The reagents used in the study including copper dichloride (CuCl2∙6H2O), hydrochloric acid (HCl), stearic acid (CH3(CH2)16COOH), sodium chloride (NaCl), acetone (C3H6O), ethanol (C2H5OH). All the reagents were analytically pure and used without further purification. Deionized water was used in the whole experiment process. 2.2. Fabrication of superhydrophobic surfaces Fig. 1 shows the main experimental process. The Be-Cu alloy was cut into sheets with a size of 25 mm × 10 mm × 2 mm. Then the sheets were sequentially polished with silicon carbide paper from 180 to 2000 mesh, ultrasonic pre-cleaned in acetone for 10 min, washed with deionized water, and dried in atmosphere condition. Measuring 60 mg stearic acid into the beaker loaded with 50 ml water, the mixture was dissolved in a water bath at 80℃ for 30 min, 2 ml 0.1 M CuCl2 and 3 ml 1 M HCl were added into the heated mixture, stirred uniformly. Electrodeposition used a DC voltage at room temperature, a Be-Cu alloy sheet as a cathode, a graphite sheet as an anode, a distance between the two electrodes of 15 mm. The operation was carried at a voltage of 5 V for different times (2 min, 5 min, 10 min, 15 min, 20 min), then cleaned 292
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with ethanol, dried under airflow, finally heated at 130℃ for 5 min. An electrodeposition for 10 min without stearic acid in the electrolyte was carried out as comparative study for chemical composition.
the obtained coating increased in thickness, the nanostructures nonuniformly shrunk during heating, resulting in gullies and nonuniform nanostructure forming where stearic acid accumulating. The wettability of the electrodeposition coating surfaces was measured by a contact angle meter. With the deposition time increasing, the static contact angle changed as shown in the Fig. 3a, from the curve it can be concluded that the water contact angles are all greater than 150°. When the deposition time is 10 min, the maximum contact angle is 163 ± 4°. As the deposition time goes on increase, the contact angle began to decrease. The sliding angle varies counter to the contact angle with the minimum of 1.7 ± 0.2°. Combined with the surface morphologies by SEM, it can be found that complex nanostructure plays a key role in the water-repel of the surfaces. Fig. 3d shows the change of surface roughness at different electrodeposition time measured by laser confocal microscope. It can be seen from the curve that the roughness Ra of the bare substrate is 0.51 μm, polished by sandpaper. When the deposition time increases, the surface roughness increases, which is consistent with the surface morphologies of SEM. When the electrodeposition time reaches 20 min, the surface roughness Ra is 1.12 μm. These coatings made the surface roughness increase not so largely, it can meet the roughness requirements of non-cooperation area. Although the surface roughness increases after 20 min of electrodeposition, the contact angle decreased due to the excessive deposition time that causes the undesirable content and distribution change of stearic acid on the coating. The air film formed by nanostructures effectively prevents the liquid from permeating the surface. As shown in the Fig. 3b, the superhydrophobic surface inserted into the water formed the air film, while the bare substrate not. A large amount of air exists in the contact interface, resulting in an increase on the contact angle. As the air film exists, the phenomenon can be explained according to the Cassie-Baxter model [39], when the proportion of air becomes larger, the contact angle increased.
2.3. Characterization 2.3.1. Surface characterization The surface morphologies of the coating obtained on Be-Cu alloy sheets were observed by scanning electron microscope (SEM, Hitachi SU8000) at 10 kV, the 3D morphologies were characterized using a laser confocal microscope (OLS3000; Olympus, Japan) to evaluate the roughness of the coating surfaces, chemical composition of the as-prepared sample was characterized by energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). A contact angle meter system (JC2000C1; Shanghai Zhongchen Digital Technic Apparatus Co, Ltd. China) was used to measure contact angle and sliding angle in air at room temperature. And the water droplet of 5 μL was used in each test. The values of contact angle and roughness were obtained by average of five different areas. 2.3.2. Electrochemical experiments The corrosion resistance of the superhydrophobic coatings was examined by electrochemical tests [38], including potentiodynamic polarization curve (Tafel) and electrochemical impedance spectroscopy (EIS) in 3.5 wt% NaCl solution at room temperature on the electrochemical workstation (CHI660D, CH Instruments Inc.). A three-electrode system was used in the test: a saturated calomel electrode (Ag/ AgCl, 3 M KCl) was used as reference electrode, while the counter electrode and the working electrode severally used a graphite electrode and the as-prepared samples. The working area of the working electrode was 1 cm2. The scanning range of the Tafel curves was −0.05 V to −0.3 V, with scanning rate of 1 mV/s. The EIS tests were carried out from 105 to 1 Hz of the AC signal frequencies under open circuit potential with the amplitude of the perturbation voltage of 5 mV. The asprepared samples were immersed in the electrolyte for 20 min prior to electrochemical experiments, each test was repeated more than three times to verify the repeatability of the results.
3.2. Chemical composition The chemical composition of the surfaces was analyzed using energy dispersive X-ray spectroscopy (EDS). The coating electrodeposition for 10 min was measured and an electrolyte without stearic acid was used as a comparison. The EDS spectrums are shown in Fig. 4. Fig. 4a shows the result of the electrolyte containing stearic acid and Fig. 4b shows the result without stearic acid. The percentages of weight and atomicity of the coatings are shown in Table 1. Combined with the test results, it is found that the weight percentage of C element on the superhydrophobic surface is 6.13% and the number of atoms accounts for 24.12%. The surface without stearic acid doesn’t contain C element. Stearic acid plays a key role in the wettability of the coating to low surface energy. The O element of the superhydrophobic surface is mainly derived from stearic acid, while the O element weight percentage without stearic acid is 4.38%, and atomic percentage is 15.40%, higher than the superhydrophobic surface. It is because Cu electrodeposited on the surface is oxidized to form copper oxide. The study indicates that surface modified by low surface energy chemicals is not easily oxidized. X-ray photoelectron spectroscopy (XPS) was utilized to investigate the chemical composition of the superhydrophobic surface electrodeposition for 10 min. The results are shown in Fig. 5. Fig. 5a shows the survey spectrum of the superhydrophobic surface. The peaks of C, O and Cu element are indicated in the spectrum. It is found that a stearic acid layer has been linked on the superhydrophobic coating, which reduces the surface energy significantly. Fig. 5b is the high-resolution spectrum of C1s. The peaks of C element can be resolved into two components. The peak at 284.54 eV corresponds to methyl (eCH3) and methylene (eCH2), and the peak at 288.48 eV corresponds to carboxyl functional group (eCOOH) [34]. Comparing the peak areas, it implies that the peaks of methylene and methyl groups are significantly higher
3. Results and discussion 3.1. Surface morphology and wettability The microscopic morphologies of the surfaces were observed by SEM, as shown in Fig. 2, which shows the images of low-magnification and high-magnification surface morphologies obtained by one-step electrodeposition processing of different time. Fig. 2(c2) is a typical superhydrophobic surface nanostructure. As can be seen from the image, the structures exhibited a chain of particles, and they grew based on the surface. The enlarged view shows that the chain structure is small grainy crystals that piled up, and new chains were grown base on the branches, accumulated to form a layer nanostructure. Since the surface structure is a multimodal growth type, many tiny voids were generated, providing geometry conditions for forming superhydrophobic surfaces. Comparing the surface morphologies of different electrodeposition time, it is found that the original surface of the substrate can be observed at the deposition time of 2 min (shown in Fig. 2(a1)). The particle structures deposited were sparse, and the nanostructures on the surfaces were very nonuniform. With the deposition time increasing, the bare substrate was gradually covered by the cross-link chain structure, and the nanostructure on the surface tended to be uniform (shown in Fig. 2(b1)). As the deposition time increases continuously, the chains were more crossed, and the voids distribution became more uniform (shown in Fig. 2(c1)). When the deposition time exceeds 15 min (shown in Fig. 2(d1)), gullies appear on the coating, as can be seen in the Fig. 2(d2). Because the electrodeposition time is too long, 293
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Fig. 2. SEM images of electrodeposition coating on the Be-Cu alloy at different electrodeposition time (a1) 2 min (b1) 5 min (c1) 10 min (d1) 15 min (e1) 20 min, (a2)–(e2) are the accordingly magnification images, respectively.
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Fig. 4. EDS of the as-prepared surfaces. (a) electrodeposition for 10 min with stearic acid and (b) electrodeposition for 10 min without stearic acid.
Table 1 Summary of element composition in EDS research of the coating electrodeposition for 10 min with (a) / without (b) stearic acid. element
C O Cu
Fig. 3. (a) Variation in the water contact angle and sliding angle of the asprepared surfaces as function of electrodeposition time. (b) and (c) are the optical photographs of the coating electrodeposition for 10 min and the bare BeCu alloy substrate immersed in the water. (d) Variation in the roughness of the as-prepared surfaces as function of electrodeposition time.
with stearic acid
without stearic acid
weight/%
atomic/%
weight/%
atomic/%
6.13 2.71 91.16
24.12 8.02 67.86
– 4.38 95.62
– 15.40 84.60
processes on the cathode are as follows: Cu2+ + 2e− → Cu Cu2+ + 2CH3(CH2)16COOH →Cu [CH3(CH2)16COO]2 + 2H+
than those of carboxyl functional groups, which is corresponding to the molecular structure of stearic acid. Fig. 5c shows the high-resolution region of Cu2p. It can be seen that the two main peaks are 931.33 eV and 951.23 eV, corresponding to Cu2p3/2 and Cu2p1/2, respectively, representing the bonding mode of pure metallic copper, and there are two peaks at 943.51 eV and 961.34 eV, attributed to CueO coordination [13,40]. This means that O]Ce groups are bonded with Cu2+. From the aspect of the peak area ratio, CueO bonds are less, and the coating exists in the form of pure copper. In the mixed electrolyte, stearic acid is dissociated, and H+, CH3(CH2)16COO−, Cu2+ are present in the electrolyte and react under the electric field. The main reaction
2H+ + 2e− →H2 ↑
3.3. Corrosion resistance Metal surfaces would damage if contact liquid environment corrosive frequently, and improving the performance of the corrosion resistance of the metal is very necessary in engineering applications. For Be-Cu alloy, the service life of the product can be effectively enhanced when the corrosion resistance is improved. The superhydrophobic 295
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Fig. 6. Tafel curves of the bare Be-Cu alloy substrate, coatings electrodeposition for 10 min and 20 min in 3.5 wt% NaCl solution. Table 2 Electrochemical parameters from the Tafel curves of the bare Be-Cu alloy and surface coatings electrodeposited for different time. Sample
Ecorr(V)
icorr(A∙cm−2)
ηIE(%)
bare Be-Cu alloy electrodeposition for 10 min electrodeposition for 20 min
−1.20 × 10-1 −9.2 × 10-2 −9.1 × 10-2
2.609 × 10−4 3.710 × 10−5 6.309 × 10−5
– 85.8 75.8
ηIE =
i 0−icorr × 100% i0
(1)
Where i 0 and icorr are the current density of the bare Be-Cu alloy and the coatings respectively. In general, higher corrosion potential and lower corrosion current density represent for better corrosion resistance. The data shows that after electrodeposition, the surface was superhydrophobic, and the anticorrosion potential of the coating surface improved compared with the smooth surface, while the corrosion current density reduced. The thickness of the coating has a great influence on the corrosion current density [3,21]. The Ecorr of the bare Be-Cu alloy surface was −1.20 × 10−1 V, in contrast, the Ecorr of the surfaces electrodeposition for 10 min and 20 min were −9.2 × 10−2 V and −9.1 × 10−2 V correspondingly. The icorr of the bare surface was 2.609 × 10−4 A cm−2, the coating electrodeposition for 10 min was 3.710 × 10−5 A cm−2, electrodeposition for 20 min was 6.309 × 10−5 A cm−2, the corrosion current density of superhydrophobic surfaces reduced so much. As for ηIE , they were calculated that the electrodeposition for 10 min was 85.8%, electrodeposition for 20 min was 75.8%. The coating electrodeposition for 10 min performed the better corrosion resistance. Further research, EIS tests were carried out as the supplement of the Tafel curves to evaluate the anti-corrosion of the as-prepared superhydrophobic coatings. Fig. 7a is the Nyquist plot of the bare surface and the coatings. It can be found that the impedance semicircle diameter of the coating electrodeposition for 10 min is the largest, the bare Be-Cu alloy is the least, shown in the Nyquist plot, the largest impedance semicircle diameter was 25 times to the smallest one. It is known that the diameter represents the polarization resistance of the samples [36], the surface electrodeposition for 10 min performed the best anti-corrosion property. The Bode plot is shown in Fig. 7b, in the high-frequent part, |Z| of the three samples were much close, while in the low-frequent part, the |Z| of the coating electrodeposition for 10 min was up to 417 Ω cm2, 25 times of the bare surface. When electrodeposition for 20 min, the anticorrosion was lower than 10 min, because of the wettability of the coatings lower than electrodeposition for 10 min. The wetting of the coating surfaces is in accord with the Cassie-
Fig. 5. XPS of the as-prepared surface electrodeposition for 10 min. (a) survey spectrum, (b) C1s region, (c) Cu2p region.
coating can effectively improve the corrosion resistance of the material surface, so the use of this coating on the Be-Cu alloy products is significant. In order to test the corrosion resistance property of the asprepared coatings, the surface was subjected to electrochemical corrosion resistance analysis, the Tafel curves and EIS of the samples were measured in the 3.5 wt% NaCl solution at room temperature. The Tafel curves of the bare Be-Cu alloy and the surfaces electrodeposition for 10 min and 20 min are shown in the Fig. 6, some parameters related to the Tafel curves are listed in the Table 2 such as corrosion potential (Ecorr ), corrosion current density (icorr ) and the inhibition efficiency (ηIE), where ηIE can get by the formula [41]: 296
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Fig. 8. Self-cleaning performance evolution. (a) the as-prepared coating electrodeposition for 10 min, (b) the bare Be-Cu alloy substrate. (a2) and (b2) the substrates sloped by 5°, (a3) and (b3) the substrates laid flat and waterdrop added vertically.
Fig. 8a3 and b3. The superhydrophobic surface formed a sphere and the surrounding particles were rolled up, while the smooth surface droplets spread the surface. The results show that the as-prepared superhydrophobic surface has good self-cleaning property and can be used in practical pollution applications after verification. When water droplets flow through the coating surface, it can carry dust and escape from the surface together, which presents anti-fouling effect compared with the smooth substrate, the superhydrophobic surface has no water droplets remaining, reflecting the water resistance of the coating. Taking advantage of its non-wetting properties, the coating can be used in lossless liquid transport.
Fig. 7. EIS of the bare Be-Cu alloy substrate and coatings electrodeposition for 10 min and 20 min in 3.5 wt% NaCl solution. (a) the Nyquist plot, the inset is the magnification in the low impedance region, (b) the Bode plot (|Z| changes as the function of frequency ranging from 1 to 105 Hz).
Baxter case, that is related to heterogeneous wetting, there is air film between the liquid and the coating surface, where the coating has water repellent effect, so the real contact area between the electrolyte and surface nanostructure is very small. In the other hand, active corrosive sites are occupied by hydrophobic molecules, decreased the adsorption of corrosive ions on the surface effectively, which inhibits the corrosion reaction, at the same time, the hydrophobic molecular layer is a barrier for charge transfer, stearic acid chain inhibits charge transfer from coating to liquid [42,43]. In conclusion, superhydrophobic coating enhances the corrosion resistance of surface.
4. Conclusion In this paper, a method of one-step electrodeposition to fabricate superhydrophobic coating on the surface of C17200 substrates was proposed. Using an electrolyte mixture of heated stearic acid, hydrochloric acid, and cupric chloride, the Be-Cu alloy substrate acted as a cathode, forming a superhydrophobic coating on the surface. SEM, EDS and XPS tests were used to analyze the morphology and chemical composition of the surface. The effects of electrodeposition time of the superhydrophobic coating were studied. When the electrodeposition time was 10 min, the high static contact angle up to 163 ± 4° and sliding angle of 1.7 ± 0.2° was obtained. The corrosion resistance of superhydrophobic coatings can be improved by 25 times compared with bare Be-Cu alloy through electrochemical tested. The experiment results show that superhydrophobic surface has a good self-cleaning performance. In addition, this method is high fabrication efficiency by using electrodeposition method, and the working fluid is low-cost without pollution, solving the problem of complex process.
3.4. Self-cleaning property Self-cleaning is a property of superhydrophobic surface [15,44]. The fact that the lotus glowing beneath the dirt is an indication of the selfcleaning property of the super hydrophobic surface of the lotus leaf [13]. The self-cleaning property can be applied to many occasions such as anti-pollution and dustproof. Self-cleaning tests were performed on the as-prepared superhydrophobic surfaces. Fig. 8 shows an experimental comparison of a superhydrophobic coating with a smooth substrate, with quartz sand particles on the surfaces, as shown in Fig. 8a1 and b1. Sloped the substrates by 5°, and used a pipette to jet on the surface, as shown in Fig. 8a2 and b2. On the superhydrophobic surface, droplets carried the quartz sand particles off the surface, and the path of the droplets movement is shown in the photograph, while the droplets penetrated into particles on the smooth surface. Then the substrates laid flat and drops of water were dropped vertically, the results are shown in
Acknowledgement This work is supported by National Nature Science Foundation of China (Grant Nos. 51775145). 297
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References
[23] W. Xu, Y. Hu, W. Bao, X. Xie, Y. Liu, A. Song, J. Hao, Superhydrophobic copper surfaces fabricated by fatty acid soaps in aqueous solution for excellent corrosion resistance, Appl. Surf. Sci. 399 (2017) 491–498. [24] L.B. Boinovich, A.M. Emelyanenko, A.D. Modestov, A.G. Domantovsky, K.A. Emelyanenko, Synergistic effect of superhydrophobicity and oxidized layers on corrosion resistance of aluminum alloy surface textured by nanosecond laser treatment, ACS Appl. Mater. Interfaces 7 (2015) 19500–19508. [25] F. Yang, J.E. Efome, D. Rana, T. Matsuura, C. Lan, Metal–Organic frameworks supported on nanofiber for desalination by direct contact membrane distillation, ACS Appl. Mater. Interfaces 10 (2018) 11251–11260. [26] S. Ye, Q. Cao, Q. Wang, T. Wang, Q. Peng, A highly efficient, stable, durable, and recyclable filter fabricated by femtosecond laser drilling of a titanium foil for oilwater separation, Sci. Rep.-UK 6 (2016). [27] C. Ngo, D. Chun, Fast wettability transition from hydrophilic to superhydrophobic laser-textured stainless steel surfaces under low-temperature annealing, Appl. Surf. Sci. 409 (2017) 232–240. [28] S. Sarbada, Y.C. Shin, Superhydrophobic contoured surfaces created on metal and polymer using a femtosecond laser, Appl. Surf. Sci. 405 (2017) 465–475. [29] J. Long, P. Fan, D. Gong, D. Jiang, H. Zhang, L. Li, M. Zhong, Superhydrophobic Surfaces Fabricated by Femtosecond Laser with Tunable Water Adhesion: From Lotus Leaf to Rose Petal, ACS Appl. Mater. Interfaces 7 (2015) 9858–9865. [30] H. Wang, Q. Yao, C. Wang, B. Fan, Q. Sun, C. Jin, Y. Xiong, Y. Chen, A simple, onestep hydrothermal approach to durable and robust superparamagnetic, superhydrophobic and electromagnetic wave-absorbing wood, Sci. Rep.-UK 6 (2016). [31] L. Jia, A. Petretic, G. Molev, G. Guerin, I. Manners, M.A. Winnik, Hierarchical polymer–carbon nanotube hybrid mesostructures by crystallization-driven self-assembly, ACS Nano 9 (2015) 10673–10685. [32] H.M. Forooshani, M. Aliofkhazraei, A.S. Rouhaghdam, Superhydrophobic aluminum surfaces by mechanical/chemical combined method and its corrosion behavior, J. Taiwan Inst. Chem. E 72 (2017) 220–235. [33] H. Wang, Z. Hu, Y. Zhu, S. Yang, K. Jin, Y. Zhu, toward easily enlarged superhydrophobic materials with stain-resistant, oil–water separation and anticorrosion function by a water-based one-step electrodeposition method, Ind. Eng. Chem. Res. 56 (2017) 933–941. [34] C. Chen, S. Yang, L. Liu, H. Xie, H. Liu, L. Zhu, X. Xu, A green one-step fabrication of superhydrophobic metallic surfaces of aluminum and zinc, J. Alloy Compd. 711 (2017) 506–513. [35] S. Cui, S. Lu, W. Xu, B. Wu, Fabrication of superhydrophobic Pt 3 Fe/Fe surface for its application, J. Solid State Chem. 254 (2017) 14–24. [36] Y. Liu, J. Xue, D. Luo, H. Wang, X. Gong, Z. Han, L. Ren, One-step fabrication of biomimetic superhydrophobic surface by electrodeposition on magnesium alloy and its corrosion inhibition, J. Colloid Interface Sci. 491 (2017) 313–320. [37] S. Ou, K. Wang, Y. Hsu, Superhydrophobic NiTi shape memory alloy surfaces fabricated by anodization and surface mechanical attrition treatment, Appl. Surf. Sci. 425 (2017) 594–602. [38] H. Qian, M. Li, Z. Li, Y. Lou, L. Huang, D. Zhang, D. Xu, C. Du, L. Lu, J. Gao, Musselinspired superhydrophobic surfaces with enhanced corrosion resistance and dualaction antibacterial properties, Mater. Sci. Eng. C 80 (2017) 566–577. [39] A. Marmur, Wetting on hydrophobic rough surfaces: to be heterogeneous or not to be? Langmuir 19 (2003) 8343–8348. [40] W. Yang, J. Li, P. Zhou, L. Zhu, H. Tang, Superhydrophobic copper coating: Switchable wettability, on-demand oil-water separation, and antifouling, Chem. Eng. J. 327 (2017) 849–854. [41] S. Yuan, S.O. Pehkonen, B. Liang, Y.P. Ting, K.G. Neoh, E.T. Kang, Superhydrophobic fluoropolymer-modified copper surface via surface graft polymerisation for corrosion protection, Corros. Sci. 53 (2011) 2738–2747. [42] L.B. Boinovich, A.M. Emelyanenko, A.D. Modestov, A.G. Domantovsky, A.A. Shiryaev, K.A. Emelyanenko, O.V. Dvoretskaya, A.A. Ganne, Corrosion behavior of superhydrophobic aluminum alloy in concentrated potassium halide solutions: when the specific anion effect is manifested, Corros. Sci. 112 (2016) 517–527. [43] L.B. Boinovich, A.M. Emelyanenko, K.A. Emelyanenko, A.D. Modestov, A.G. Domantovsky, Not simply repel water: the diversified nature of corrosion protection by superhydrophobic coatings, Mendeleev Commun. 27 (2017) 254–256. [44] W. Sun, L. Wang, Z. Yang, S. Li, T. Wu, G. Liu, Fabrication of polydimethylsiloxanederived superhydrophobic surface on aluminium via chemical vapour deposition technique for corrosion protection, Corros. Sci. 128 (2017) 176–185.
[1] H. Yang, Y. He, Z. Wu, J. Miao, F. Yang, Z. Lu, Fabrication of a superhydrophobic and high-glossy copper coating on aluminum substrates, Appl. Surf. Sci. 433 (2018) 1192–1196. [2] E.J.Y. Ling, V. Uong, J. Renault-Crispo, A. Kietzig, P. Servio, Reducing ice adhesion on nonsmooth metallic surfaces: wettability and topography effects, ACS Appl. Mater. Interfaces 8 (2016) 8789–8800. [3] Y. Tuo, H. Zhang, W. Chen, X. Liu, Corrosion protection application of slippery liquid-infused porous surface based on aluminum foil, Appl. Surf. Sci. 423 (2017) 365–374. [4] E. Liu, L. Li, G. Wang, Z. Zeng, W. Zhao, Q. Xue, Drag reduction through selftexturing compliant bionic materials, Sci. Rep.-UK 7 (2017) 40038. [5] S. Bano, U. Zulfiqar, U. Zaheer, M. Awais, I. Ahmad, T. Subhani, Durable and recyclable superhydrophobic fabric and mesh for oil-water separation, Adv. Eng. Mater. 20 (2018) 1700460. [6] G. Wang, Z. Zeng, H. Wang, L. Zhang, X. Sun, Y. He, L. Li, X. Wu, T. Ren, Q. Xue, Low drag porous ship with superhydrophobic and superoleophilic surface for oil spills cleanup, ACS Appl. Mater. Interfaces 7 (2015) 26184–26194. [7] Z. Zhang, H. Wang, Y. Liang, X. Li, L. Ren, Z. Cui, C. Luo, One-step fabrication of robust superhydrophobic and superoleophilic surfaces with self-cleaning and oil/ water separation function, Sci. Rep.-UK 8 (2018). [8] Y. Qing, C. Hu, C. Yang, K. An, F. Tang, J. Tan, C. Liu, Rough structure of electrodeposition as a template for an ultrarobust self-cleaning surface, ACS Appl. Mater. Interfaces 9 (2017) 16571–16580. [9] E. Battista, M.L. Coluccio, A. Alabastri, M. Barberio, F. Causa, P.A. Netti, E. Di Fabrizio, F. Gentile, Metal enhanced fluorescence on super-hydrophobic clusters of gold nanoparticles, Microelectron. Eng. 175 (2017) 7–11. [10] L. Xiao, M. Deng, W. Zeng, B. Zhang, Z. Xu, C. Yi, G. Liao, Novel robust superhydrophobic coating with self-cleaning properties in air and oil based on rare earth metal oxide, Ind. Eng. Chem. Res. 56 (2017) 12354–12361. [11] J. Brassard, J. Laforte, C. Blackburn, J. Perron, D.K. Sarkar, Silicone based superhydrophobic coating efficient to reduce ice adhesion and accumulation on aluminum under offshore arctic conditions, Ocean Eng. 144 (2017) 135–141. [12] V. Jokinen, E. Kankuri, S. Hoshian, S. Franssila, R.H.A. Ras, Superhydrophobic blood-repellent surfaces, Adv. Mater. (2018) 1705104. [13] W. Jiang, M. Mao, W. Qiu, Y. Zhu, B. Liang, Biomimetic superhydrophobic engineering metal surface with hierarchical structure and tunable adhesion: design of microscale pattern, Ind. Eng. Chem. Res. 56 (2017) 907–919. [14] N. Karthik, T.N.J.I. Edison, Y.R. Lee, M.G. Sethuraman, Fabrication of corrosion resistant mussel-yarn like superhydrophobic composite coating on aluminum surface, J. Taiwan Inst. Chem. E 77 (2017) 302–310. [15] Z. Kang, W. Li, Facile and fast fabrication of superhydrophobic surface on magnesium alloy by one-step electrodeposition method, J. Ind. Eng. Chem. 50 (2017) 50–56. [16] L.B. Boinovich, E.B. Modin, A.R. Sayfutdinova, K.A. Emelyanenko, A.L. Vasiliev, A.M. Emelyanenko, Combination of functional nanoengineering and nanosecond laser texturing for design of superhydrophobic aluminum alloy with exceptional mechanical and chemical properties, ACS Nano 11 (2017) 10113–10123. [17] T. Xiang, Y. Han, Z. Guo, R. Wang, S. Zheng, S. Li, C. Li, X. Dai, Fabrication of inherent anticorrosion superhydrophobic surfaces on metals, ACS Sustain. Chem. Eng. 6 (2018) 5598–5606. [18] I. Vilaró, J.L. Yagüe, S. Borrós, Superhydrophobic Copper Surfaces with Anticorrosion Properties Fabricated by Solventless CVD Methods, ACS Appl. Mater. Interfaces 9 (2016) 1057–1065. [19] Y. Yildiz, M.M. Sundaram, K.P. Rajurkar, Empirical modeling of the white layer thickness formed in electrodischarge drilling of beryllium–copper alloys, Int. J. Adv. Manuf. Technol. 66 (2013) 1745–1755. [20] S. Dong, Z. Wang, Y. Wang, High-speed electrochemical discharge drilling (HSECDD) for micro-holes on C17200 beryllium copper alloy in deionized water, Int. J. Adv. Manuf. Technol. 88 (2017) 827–835. [21] S. Dong, Z. Wang, Y. Wang, X. Bai, Y.Q. Fu, B. Guo, C. Tan, J. Zhang, P. Hu, Roll-toRoll Manufacturing of Robust Superhydrophobic Coating on Metallic Engineering Materials, ACS Appl. Mater. Interfaces 10 (2018) 2174–2184. [22] Y. Cheng, S. Lu, W. Xu, R. Boukherroub, S. Szunerits, W. Liang, Controlled fabrication of NiO/ZnO superhydrophobic surface on zinc substrate with corrosion and abrasion resistance, J. Alloy. Compd. 723 (2017) 225–236.
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