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The morphology change of Co coatings prepared by cathode plasma electrolytic deposition
Materials Letters 153 (2015) 92–95
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
The morphology change of Co coatings prepared by cathode plasma electrolytic deposition Cheng Quan, Yedong He n Beijing Key Laboratory for Corrosion, Erosion and Surface Technology, University of Science and Technology Beijing, Beijing 100083, China
art ic l e i nf o
a b s t r a c t
Article history: Received 16 January 2015 Accepted 4 April 2015 Available online 14 April 2015
Co coatings were prepared by conventional electrode position and cathode plasma electrolytic deposition respectively in the electrolyte with different CoSO4 and H2SO4 concentration. The morphologies of coatings were investigated by optical microscope and scanning electron microscope. It is found that the morphology change of Co coatings prepared by cathode plasma electrolytic deposition is quite different from that of conventional electrodeposition. To obtain uniform and dense Co coatings by cathode plasma electrolytic deposition, lower CoSO4 concentration and higher H2SO4 concentration are required in the electrolyte, compared with that of conventional electrodeposition. Otherwise, the deposited Co coatings will be rough or dendritical in the electrolyte with higher CoSO4 concentration and lower H2SO4 concentration. & 2015 Elsevier B.V. All rights reserved.
Keywords: Electrodeposition Microstructure Cathode plasma electrolytic deposition Coating
1. Introduction Plasma electrolysis [1] is an advanced technique in coating preparation and surface modification with specific properties, such as high hardness [2–4], excellent adhesion [5,6], nanocrystalline structure [7–9], favorable corrosion and wear resistance [10–12]. Cathode plasma electrolytic deposition (CPED) is a part of plasma electrolysis. It’s an environmental friendly technique to prepare metal, alloy and composite coatings [1,11,13–16]. Compared with conventional electrodeposition, CPED requires a much higher voltage and the discharge breakdown of the gaseous envelope of the cathode surface [1,6]. There are also a lot of changes in the electrode process of CPED. Basing on the conventional electrolyte composition, people mayn’t obtain high quality metal coatings by CPED every time. The deposited coatings are always rough or porous [6,11]. In this study, Co coatings as examples were deposited by conventional electrodeposition and CPED respectively in the electrolyte with different CoSO4 and H2SO4 concentration. The morphology change of Co coatings were investigated in order to find the law to prepare uniform and dense metal coatings by CPED.
steels of 15 mm 10 mm 4 mm were selected as the samples after polished to 2000-grit and cleaned in ethanol ultrasonically. The distance between anode and cathode is about 6–8 mm. A vacuum pump was used for electrolyte recycling. A pulsed power supply was applied to coating preparation. In CPED process, the sample was covered with electrolyte sufficiently at first. Then the voltage was increased until bright micro-arcs can be observed on the surface of the sample. A traditional electrolytic bath was used for conventional electrodeposition. Table 1 shows the electrodeposition parameters and electrolyte composition of the two methods. The CoSO4 concentration should be adjusted to about 250 g L 1 to obtain uniform and dense coatings according to the conventional electrolyte composition [17]. There are no additives in the electrolyte, to avoid the formation of other compounds. The surface and cross-sectional morphologies of the deposited coatings were characterised by optical microscope (Kenyence VHX-600) and scanning electron microscope (JSM-6480A).
2. Material and methods Fig. 1 shows the schematic diagram of CPED device. High purity graphite with bottom holes was used as the anode. 304 stainless n
Corresponding author. Tel. /fax: þ86 10 62333957. E-mail address: [email protected] (Y. He).
http://dx.doi.org/10.1016/j.matlet.2015.04.024 0167-577X/& 2015 Elsevier B.V. All rights reserved.
Fig. 1. Schematic diagram of CPED device.
C. Quan, Y. He / Materials Letters 153 (2015) 92–95
3. Results Fig. 2 shows the surface and cross-sectional morphologies of Co coatings prepared in the electrolyte with different CoSO4 and H2SO4 concentration by conventional electrodeposition and CPED, respectively. In conventional electrodeposition process, uniform and dense Co coating was deposited with 250 g L 1 CoSO4 (Fig. 2a1); rough and porous Co coating was deposited with 80 g L 1 CoSO4 (Fig. 2a2); little Co powders and dendrites were deposited with 10 g L 1 CoSO4 (Fig. 2a3). However, in CPED process, a mass of typical Co dendrites of poor adhesion with the
Table 1 Electrodeposition parameters and electrolyte composition of the two methods.
CoSO4 (g L 1) H2SO4 (g L 1) Voltage (V) Current density (A dm 2) Frequency (Hz) Duty ratio (%) Time (min)
CPED
Conventional electrodeposition
250,80,10 250 40 80,120,160 100–120 60–100 100–300
250,80,10 40 2–5 3–4
2000 80 3
– – 60
93
substrate were deposited with 250 g L 1 CoSO4 (Fig. 2b1); Co coating with high roughness was deposited with 80 g L 1 CoSO4 (Fig. 2b2); uniform and dense Co coating with typical molten morphology was deposited with 10 g L 1 CoSO4 (Fig. 2b3). These experimental results demonstrate that the morphology change of Co coatings prepared in the electrolyte with different CoSO4 concentration by conventional electrodeposition and CPED are completely opposite. In addition, the increase of H2SO4 concentration has an obvious effect on coating morphology in CPED process. In the electrolyte with 250 g L 1 CoSO4, dense Co coating was deposited although there were still dendrites formed on the coating surface with 80 g L 1 H2SO4 (Fig. 2c1); Co coating with high roughness was deposited with 120 g L 1 H2SO4 (Fig. 2c2); uniform and dense Co coating with typical molten morphology was deposited with 160 g L 1 H2SO4 (Fig. 2c3). Furthermore, the depositing rate of CPED is much higher than that of conventional electrodeposition by comparing with the coating thicknesses.
4. Discussion Fig. 3a shows the concentration gradient of metal cations in the diffusion layer of the cathode surface in conventional electrodeposition process. If the transfer rate of metal cations in the
Fig. 2. Surface and cross-sectional morphologies of Co coatings prepared in the electrolyte with different CoSO4 concentration: (a1) 250 g L 1 (a2) 80 g L 1 (a3) 10 g L 1 by conventional electrodeposition and (b1) 250 g L 1 (b2) 80 g L 1 (b3) 10 g L 1 by CPED when the H2SO4 concentration is 40 g L 1, and with different H2SO4 concentration: (c1) 80 g L 1 (c2) 120 g L 1 (c3) 160 g L 1 by CPED when the CoSO4 concentration is 250 g L 1.
94
C. Quan, Y. He / Materials Letters 153 (2015) 92–95
Fig. 3. (a) The concentration gradient of metal cations in the diffusion layer of the cathode surface in conventional electrodeposition process; (b) The virtual condition of the diffusion layer on the cathode surface in CPED process.
diffusion layer equals to the electrochemical reduction rate at the cathode with the reaction:M n þ þ ne ¼ M, the current density iM is known as the steady state diffusion current density: iM ¼ iλ ¼ nFDM kS
c0M csM
δ
ð1Þ
where i is the current density, λ is the current efficiency of the electrochemical reduction reaction, n is the valence of metal cations, F is the Faraday constant, DM is the diffusion coefficient, c0M and csM are the concentration of metal cations in the bulk and at the cathode respectively, δ is the thickness of the diffusion layer. ks is defined as the ratio of the liquid phase per unit area, which is mainly determined by hydrogen evolution reaction:2H þ þ 2e ¼ H 2 . If there is only electrochemical reduction of metal cations without hydrogen evolution at the cathode, ks is 1. When csM -0, the concentration gradient of metal cations reaches maximum value, and the diffusion current density of metal cations reaches a limiting value id(M), which can be expressed as: idðMÞ ¼ id λ ¼ nFDM kS
c0M
δ
ð2Þ
where id is the limiting current density, corresponding to the limiting diffusion current density of metal cations id(M). If iM o idðMÞ , the electrode process is controlled by electrochemical reduction of metal cations, so the deposited coatings will be uniform and dense; if iM Z idðMÞ , the electrode process is controlled by mass transfer process, so metal cations are easier to be deposited on the bulges preferentially, leading to form rough or dendritical deposits [17]. In conventional electrodeposition process, ks is close to 1 for the weak hydrogen evolution reaction, and δA is thin (Fig. 3a), according to Eq. (2), id(M) is very high. Therefore, the electrode process may be controlled by the electrochemical reduction reaction, or the mass transfer of metal cations in the diffusion layer. According to Eq. (2), the CoSO4 concentration c0M is proportional to id(M), so high CoSO4 concentration will increase id(M), which makes iM o idðMÞ , leading to form uniform and dense Co coatings (Fig. 2a1). On the contrary, low CoSO4 concentration will decrease id(M), which makes iM Z idðMÞ , leading to form rough and porous deposits (Fig. 2a2), even powders or dendrites (Fig. 2a3). Fig. 3b shows the virtual condition of the diffusion layer on the cathode surface in CPED process. Owing to the formation of massive hydrogen bubbles and plasma arcs in the diffusion layer [11], ks is much less than 1 and δB is very thick, resulting in id(M) is much smaller than that of conventional electrodeposition. In addition, the depositing current density iM is very high, so iM c idðMÞ . Therefore, the electrode process is completely controlled
by the mass transfer process of metal cations in the diffusion layer of the cathode surface. If there’re no plasma arcs, the deposited coatings will always be rough or dendritical. However, in the electrolyte with low CoSO4 concentration, the depositing rate is slow, so the bits of deposits can be melted by plasma arcs sufficiently and solidify rapidly [1,11]. As a result, the deposited Co coating becomes uniform and dense, demonstrating a typical molten morphology (Fig. 2b3). On the other hand, the depositing rate is so fast in the electrolyte with high CoSO4 concentration that the energy of plasma arcs is not enough to melt the massive Co deposits. In the end, the Co coating becomes rough (Fig. 2b2) or dendritical (Fig. 2b1). The addition of H2SO4 will decrease the current efficiency and depositing rate greatly, leading to form uniform and dense Co coatings in the electrolyte with high CoSO4 concentration (Fig. 2c).
5. Conclusions In conclusion, the morphology change of Co coatings is determined by the depositing rate and the effect of plasma arcs in CPED process. Uniform and dense Co coatings will be deposited in the electrolyte with lower CoSO4 concentration and higher H2SO4 concentration, because Co deposits can be modified by plasma arcs sufficiently with slow depositing rate. But rough or dendritical Co coatings will be formed as the CoSO4 concentration is increased or the H2SO4 concentration is decreased in the electrolyte, since Co deposits are too many to be modified by plasma arcs with fast depositing rate. This law can be a general guide to prepare uniform and dense metal coatings by CPED.
Acknowledgements This work was supported by the National Natural Science Foundation of China (Grant no. 51171021). References [1] Yerokhin A, Nie X, Leyland A, Matthews A, Dowey S. Surf Coat Technol 1999;122:73–93. [2] Shen D-J, Wang Y-L, Nash P, Xing G-Z. Mater Sci Eng, A 2007;458:240–3. [3] Béjar M, Henríquez R. Mater Des 2009;30:1726–8. [4] Guo J, Wang H, Zhu J, Zheng K, Zhu M, Yan H, et al. Electrochem Commun 2007;9:1824–7. [5] Nie X, Leyland A, Song H, Yerokhin A, Dowey S, Matthews A. Surf Coat Technol 1999;116:1055–60. [6] Gupta P, Tenhundfeld G, Daigle E, Ryabkov D. Surf Coat Technol 2007;201:8746–60. [7] Aliofkhazraei M, Sabour Rouhaghdam A, Heydarzadeh A, Elmkhah H. Mater Chem Phys 2009;113:607–12.
C. Quan, Y. He / Materials Letters 153 (2015) 92–95
[8] Paulmier T, Bell JM, Fredericks PM. Thin Solid Films 2007;515:2926–34. [9] Aliofkhazraei M, Rouhaghdam AS, Gupta P. Crit Rev Solid State Mater Sci 2011;36:174–90. [10] Nie X, Meletis E, Jiang J, Leyland A, Yerokhin A, Matthews A. Surf Coat Technol 2002;149:245–51. [11] Meletis E, Nie X, Wang F, Jiang J. Surf Coat Technol 2002;150:246–56. [12] Hussein R, Nie X, Northwood D. Electrochim Acta 2013;112:111–9.
95
[13] Aliofkhazraei M, Sabour Roohaghdam A. Electrochem Commun 2007;9:2686–91. [14] Zhao G, He Y. Surf Coat Technol 2012;206:4411–6. [15] Tokushige M, Nishikiori T, Lafouresse M, Michioka C, Yoshimura K, Fukunaka Y, et al. Electrochim Acta 2010;55:8154–9. [16] Quan C, He Y. Surf Coat Technol 2015;269:319–23. [17] Schlesinger M, Paunovic M. Modern electroplating. John Wiley & Sons; 2011.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
The morphology change of Co coatings prepared by cathode plasma electrolytic deposition Cheng Quan, Yedong He n Beijing Key Laboratory for Corrosion, Erosion and Surface Technology, University of Science and Technology Beijing, Beijing 100083, China
art ic l e i nf o
a b s t r a c t
Article history: Received 16 January 2015 Accepted 4 April 2015 Available online 14 April 2015
Co coatings were prepared by conventional electrode position and cathode plasma electrolytic deposition respectively in the electrolyte with different CoSO4 and H2SO4 concentration. The morphologies of coatings were investigated by optical microscope and scanning electron microscope. It is found that the morphology change of Co coatings prepared by cathode plasma electrolytic deposition is quite different from that of conventional electrodeposition. To obtain uniform and dense Co coatings by cathode plasma electrolytic deposition, lower CoSO4 concentration and higher H2SO4 concentration are required in the electrolyte, compared with that of conventional electrodeposition. Otherwise, the deposited Co coatings will be rough or dendritical in the electrolyte with higher CoSO4 concentration and lower H2SO4 concentration. & 2015 Elsevier B.V. All rights reserved.
Keywords: Electrodeposition Microstructure Cathode plasma electrolytic deposition Coating
1. Introduction Plasma electrolysis [1] is an advanced technique in coating preparation and surface modification with specific properties, such as high hardness [2–4], excellent adhesion [5,6], nanocrystalline structure [7–9], favorable corrosion and wear resistance [10–12]. Cathode plasma electrolytic deposition (CPED) is a part of plasma electrolysis. It’s an environmental friendly technique to prepare metal, alloy and composite coatings [1,11,13–16]. Compared with conventional electrodeposition, CPED requires a much higher voltage and the discharge breakdown of the gaseous envelope of the cathode surface [1,6]. There are also a lot of changes in the electrode process of CPED. Basing on the conventional electrolyte composition, people mayn’t obtain high quality metal coatings by CPED every time. The deposited coatings are always rough or porous [6,11]. In this study, Co coatings as examples were deposited by conventional electrodeposition and CPED respectively in the electrolyte with different CoSO4 and H2SO4 concentration. The morphology change of Co coatings were investigated in order to find the law to prepare uniform and dense metal coatings by CPED.
steels of 15 mm 10 mm 4 mm were selected as the samples after polished to 2000-grit and cleaned in ethanol ultrasonically. The distance between anode and cathode is about 6–8 mm. A vacuum pump was used for electrolyte recycling. A pulsed power supply was applied to coating preparation. In CPED process, the sample was covered with electrolyte sufficiently at first. Then the voltage was increased until bright micro-arcs can be observed on the surface of the sample. A traditional electrolytic bath was used for conventional electrodeposition. Table 1 shows the electrodeposition parameters and electrolyte composition of the two methods. The CoSO4 concentration should be adjusted to about 250 g L 1 to obtain uniform and dense coatings according to the conventional electrolyte composition [17]. There are no additives in the electrolyte, to avoid the formation of other compounds. The surface and cross-sectional morphologies of the deposited coatings were characterised by optical microscope (Kenyence VHX-600) and scanning electron microscope (JSM-6480A).
2. Material and methods Fig. 1 shows the schematic diagram of CPED device. High purity graphite with bottom holes was used as the anode. 304 stainless n
Corresponding author. Tel. /fax: þ86 10 62333957. E-mail address: [email protected] (Y. He).
http://dx.doi.org/10.1016/j.matlet.2015.04.024 0167-577X/& 2015 Elsevier B.V. All rights reserved.
Fig. 1. Schematic diagram of CPED device.
C. Quan, Y. He / Materials Letters 153 (2015) 92–95
3. Results Fig. 2 shows the surface and cross-sectional morphologies of Co coatings prepared in the electrolyte with different CoSO4 and H2SO4 concentration by conventional electrodeposition and CPED, respectively. In conventional electrodeposition process, uniform and dense Co coating was deposited with 250 g L 1 CoSO4 (Fig. 2a1); rough and porous Co coating was deposited with 80 g L 1 CoSO4 (Fig. 2a2); little Co powders and dendrites were deposited with 10 g L 1 CoSO4 (Fig. 2a3). However, in CPED process, a mass of typical Co dendrites of poor adhesion with the
Table 1 Electrodeposition parameters and electrolyte composition of the two methods.
CoSO4 (g L 1) H2SO4 (g L 1) Voltage (V) Current density (A dm 2) Frequency (Hz) Duty ratio (%) Time (min)
CPED
Conventional electrodeposition
250,80,10 250 40 80,120,160 100–120 60–100 100–300
250,80,10 40 2–5 3–4
2000 80 3
– – 60
93
substrate were deposited with 250 g L 1 CoSO4 (Fig. 2b1); Co coating with high roughness was deposited with 80 g L 1 CoSO4 (Fig. 2b2); uniform and dense Co coating with typical molten morphology was deposited with 10 g L 1 CoSO4 (Fig. 2b3). These experimental results demonstrate that the morphology change of Co coatings prepared in the electrolyte with different CoSO4 concentration by conventional electrodeposition and CPED are completely opposite. In addition, the increase of H2SO4 concentration has an obvious effect on coating morphology in CPED process. In the electrolyte with 250 g L 1 CoSO4, dense Co coating was deposited although there were still dendrites formed on the coating surface with 80 g L 1 H2SO4 (Fig. 2c1); Co coating with high roughness was deposited with 120 g L 1 H2SO4 (Fig. 2c2); uniform and dense Co coating with typical molten morphology was deposited with 160 g L 1 H2SO4 (Fig. 2c3). Furthermore, the depositing rate of CPED is much higher than that of conventional electrodeposition by comparing with the coating thicknesses.
4. Discussion Fig. 3a shows the concentration gradient of metal cations in the diffusion layer of the cathode surface in conventional electrodeposition process. If the transfer rate of metal cations in the
Fig. 2. Surface and cross-sectional morphologies of Co coatings prepared in the electrolyte with different CoSO4 concentration: (a1) 250 g L 1 (a2) 80 g L 1 (a3) 10 g L 1 by conventional electrodeposition and (b1) 250 g L 1 (b2) 80 g L 1 (b3) 10 g L 1 by CPED when the H2SO4 concentration is 40 g L 1, and with different H2SO4 concentration: (c1) 80 g L 1 (c2) 120 g L 1 (c3) 160 g L 1 by CPED when the CoSO4 concentration is 250 g L 1.
94
C. Quan, Y. He / Materials Letters 153 (2015) 92–95
Fig. 3. (a) The concentration gradient of metal cations in the diffusion layer of the cathode surface in conventional electrodeposition process; (b) The virtual condition of the diffusion layer on the cathode surface in CPED process.
diffusion layer equals to the electrochemical reduction rate at the cathode with the reaction:M n þ þ ne ¼ M, the current density iM is known as the steady state diffusion current density: iM ¼ iλ ¼ nFDM kS
c0M csM
δ
ð1Þ
where i is the current density, λ is the current efficiency of the electrochemical reduction reaction, n is the valence of metal cations, F is the Faraday constant, DM is the diffusion coefficient, c0M and csM are the concentration of metal cations in the bulk and at the cathode respectively, δ is the thickness of the diffusion layer. ks is defined as the ratio of the liquid phase per unit area, which is mainly determined by hydrogen evolution reaction:2H þ þ 2e ¼ H 2 . If there is only electrochemical reduction of metal cations without hydrogen evolution at the cathode, ks is 1. When csM -0, the concentration gradient of metal cations reaches maximum value, and the diffusion current density of metal cations reaches a limiting value id(M), which can be expressed as: idðMÞ ¼ id λ ¼ nFDM kS
c0M
δ
ð2Þ
where id is the limiting current density, corresponding to the limiting diffusion current density of metal cations id(M). If iM o idðMÞ , the electrode process is controlled by electrochemical reduction of metal cations, so the deposited coatings will be uniform and dense; if iM Z idðMÞ , the electrode process is controlled by mass transfer process, so metal cations are easier to be deposited on the bulges preferentially, leading to form rough or dendritical deposits [17]. In conventional electrodeposition process, ks is close to 1 for the weak hydrogen evolution reaction, and δA is thin (Fig. 3a), according to Eq. (2), id(M) is very high. Therefore, the electrode process may be controlled by the electrochemical reduction reaction, or the mass transfer of metal cations in the diffusion layer. According to Eq. (2), the CoSO4 concentration c0M is proportional to id(M), so high CoSO4 concentration will increase id(M), which makes iM o idðMÞ , leading to form uniform and dense Co coatings (Fig. 2a1). On the contrary, low CoSO4 concentration will decrease id(M), which makes iM Z idðMÞ , leading to form rough and porous deposits (Fig. 2a2), even powders or dendrites (Fig. 2a3). Fig. 3b shows the virtual condition of the diffusion layer on the cathode surface in CPED process. Owing to the formation of massive hydrogen bubbles and plasma arcs in the diffusion layer [11], ks is much less than 1 and δB is very thick, resulting in id(M) is much smaller than that of conventional electrodeposition. In addition, the depositing current density iM is very high, so iM c idðMÞ . Therefore, the electrode process is completely controlled
by the mass transfer process of metal cations in the diffusion layer of the cathode surface. If there’re no plasma arcs, the deposited coatings will always be rough or dendritical. However, in the electrolyte with low CoSO4 concentration, the depositing rate is slow, so the bits of deposits can be melted by plasma arcs sufficiently and solidify rapidly [1,11]. As a result, the deposited Co coating becomes uniform and dense, demonstrating a typical molten morphology (Fig. 2b3). On the other hand, the depositing rate is so fast in the electrolyte with high CoSO4 concentration that the energy of plasma arcs is not enough to melt the massive Co deposits. In the end, the Co coating becomes rough (Fig. 2b2) or dendritical (Fig. 2b1). The addition of H2SO4 will decrease the current efficiency and depositing rate greatly, leading to form uniform and dense Co coatings in the electrolyte with high CoSO4 concentration (Fig. 2c).
5. Conclusions In conclusion, the morphology change of Co coatings is determined by the depositing rate and the effect of plasma arcs in CPED process. Uniform and dense Co coatings will be deposited in the electrolyte with lower CoSO4 concentration and higher H2SO4 concentration, because Co deposits can be modified by plasma arcs sufficiently with slow depositing rate. But rough or dendritical Co coatings will be formed as the CoSO4 concentration is increased or the H2SO4 concentration is decreased in the electrolyte, since Co deposits are too many to be modified by plasma arcs with fast depositing rate. This law can be a general guide to prepare uniform and dense metal coatings by CPED.
Acknowledgements This work was supported by the National Natural Science Foundation of China (Grant no. 51171021). References [1] Yerokhin A, Nie X, Leyland A, Matthews A, Dowey S. Surf Coat Technol 1999;122:73–93. [2] Shen D-J, Wang Y-L, Nash P, Xing G-Z. Mater Sci Eng, A 2007;458:240–3. [3] Béjar M, Henríquez R. Mater Des 2009;30:1726–8. [4] Guo J, Wang H, Zhu J, Zheng K, Zhu M, Yan H, et al. Electrochem Commun 2007;9:1824–7. [5] Nie X, Leyland A, Song H, Yerokhin A, Dowey S, Matthews A. Surf Coat Technol 1999;116:1055–60. [6] Gupta P, Tenhundfeld G, Daigle E, Ryabkov D. Surf Coat Technol 2007;201:8746–60. [7] Aliofkhazraei M, Sabour Rouhaghdam A, Heydarzadeh A, Elmkhah H. Mater Chem Phys 2009;113:607–12.
C. Quan, Y. He / Materials Letters 153 (2015) 92–95
[8] Paulmier T, Bell JM, Fredericks PM. Thin Solid Films 2007;515:2926–34. [9] Aliofkhazraei M, Rouhaghdam AS, Gupta P. Crit Rev Solid State Mater Sci 2011;36:174–90. [10] Nie X, Meletis E, Jiang J, Leyland A, Yerokhin A, Matthews A. Surf Coat Technol 2002;149:245–51. [11] Meletis E, Nie X, Wang F, Jiang J. Surf Coat Technol 2002;150:246–56. [12] Hussein R, Nie X, Northwood D. Electrochim Acta 2013;112:111–9.
95
[13] Aliofkhazraei M, Sabour Roohaghdam A. Electrochem Commun 2007;9:2686–91. [14] Zhao G, He Y. Surf Coat Technol 2012;206:4411–6. [15] Tokushige M, Nishikiori T, Lafouresse M, Michioka C, Yoshimura K, Fukunaka Y, et al. Electrochim Acta 2010;55:8154–9. [16] Quan C, He Y. Surf Coat Technol 2015;269:319–23. [17] Schlesinger M, Paunovic M. Modern electroplating. John Wiley & Sons; 2011.