Corrosion Behavior and Mechanism of Carbon Ion-Implanted Magnesium Alloy

Abstract

Carbon ion implantation was conducted on an AM60 magnesium alloy with fluences between 1 × 10¹⁶ and 6 × 10¹⁶ ions/cm² and an energy of 35 keV. The microstructure and electrochemical properties of the samples were systematically characterized by X-ray photoelectron spectroscopy, X-ray diffraction, Raman scattering, scanning electron microscopy, transmission electron microscopy, and electrochemical methods. These studies reveal that a 250 nm-thick C-rich layer is formed on the surface and the Mg₂C₃ phase embeds in the ion-implanted region. The crystal structure of the Mg₂C₃ was constructed, and an electronic density map was calculated by density-functional theory calculation. The large peak in the density of states (DOS) shows two atomic p orbitals for Mg₂C₃. The main electron energy is concentrated between −50 and −40 eV, and the electron energy mainly comes from Mg (p) and Mg (s). The electrochemical experiments reveal that the E_corr is −1.35 V and I_corr is 20.1 μA/cm² for the sample implanted with the optimal fluence of 6 × 10¹⁶ ions/cm². The sample from C ion implantation gives rise to better corrosion resistance.

1. Introduction

Magnesium alloys have some obvious advantages such as light weight and recyclability, and they are more and more widely used [1,2,3,4,5]. However, the corrosion resistance of magnesium alloys is not good enough [6,7]. To date, many methods have been carried out to improve the corrosion properties of magnesium alloys such as microarc oxidation [8,9], laser cladding [10,11], and ion implantation [12,13,14,15,16]. Ion implantation causes the substrate and coating have a good binding force compared to other methods. Many ions can be used in the ion implantation. For example, Ti [17,18], Al [19,20], Zr [21,22], and Cr [23,24] ion implantation has been conducted on Mg alloys to improve the corrosion properties. Compared with that of an untreated sample, the corrosion potential of a Ti/N-treated coupon increases by over 600 mV, the corrosion current density decreases by over two orders of magnitude, and the polarization resistance increases by 66.4 times [17]. The Al ion-implanted AZ31 magnesium alloy with an ion implantation dose of 6 × 10¹⁶ ions/cm² achieved a high pitting breakdown potential of about −480 mV (saturated calomel electrode (SCE)) [20]. The Zr ion implantation sample shows a smaller I_corr due to the formation of ZrO₂ in the implanted layer [21].

In addition to metals, some nonmetals are also used for ion implantation. A Mg-Nd-Zn-Zr alloy was modified with C₂H₂ gas, and a diamond-like carbon film (DLC) was synthesized. Most of the surface region was protected in the aggressive NaCl solution [25]. The corrosion resistance of the AZ31 Mg alloy formed by N ion implantation was studied [26,27]. The results indicate that a Mg₃N₂ film is formed. The corrosion potential shift was 100 mV. Besides the corrosion resistance, the cytotoxicity properties of Mg alloys modified by ion implantation have also been investigated [28,29,30].

The corrosion performance of the magnesium alloys can be improved to a certain extent by ion implantation. The C element was also implanted into pure magnesium, and the electrochemical properties were studied by Xu [31], but the microstructure of a C layer is not well known. As a very important element, C has many physical and chemical properties, such as good electrical conductivity and tribological properties. Many new carbon-based materials are being developed, for instance, nanoporous carbon [32] and carbon layers [33].

The application of AM60 materials is limited by poor corrosion properties. The effects of C ion implantation on the AM60 magnesium alloy and related mechanism have not been reported previously. In this work, the AM60 magnesium alloy was implanted with C with different fluences, and the structural and electrochemical properties were studied in detail. The atomic structure is discussed based on both experimental and theoretical results. 2. Experimental and Theoretical Calculations

Commercially available AM60 magnesium alloy samples were cut into 15 mm × 15 mm × 2 mm pieces and used as substrates in the experiment. Before ion implantation, the samples were finely ground with SiC paper of 400, 800, 1200, 1500, and 2000 grits, sequentially, followed by polishing with fine diamond paste (average grain size, 0.5 μm) to a final roughness of approximately 0.08 ± 0.02 μm, and then they were cleaned in acetone by ultrasonication. Carbon ion implantation was performed on the PI-80A plasma ion implanter in the Plasma Laboratory of City University of Hong Kong, Hong Kong, China. During implantation, the base pressure in the vacuum chamber was 2 × 10⁻³ Pa and the acceleration voltage was 35 keV. The ion implantation fluences are shown in Table 1.

X-ray photoelectron spectroscopy (XPS, PHI-5000 versaprobe, Kanagawa, Japan) was carried with Al Kα irradiation at a sputtering rate of about 10 nm/min in order to analyze the depth of the implanted elements. The Raman scattering spectra were acquired on the HR LabRAM using a 514.5 nm argon laser, and the structure was confirmed by X-ray diffraction on the D2 Phaser X-ray diffractometer (XRD) (BRUKER, Karlsruhe, Germany) with Cu Kα radiation. The cross-sectional microstructure of the samples was observed under a transmission electron microscope (TEM, JEM-2100, Tokyo, Japan). A TEM sample with a thickness of 3 mm was cut from the center of the ion implantation surface, with a plane size of 3 mm × 0.5 mm. Then, the 0.5 mm particles were further ground and thinned. The hole was thinned near the ion implantation surface, and the observation surface was perpendicular to the ion-implanted surface. The corrosion tests were performed on an electrochemical workstation (CHI660E, Shanghai, China). A three-electrode configuration with a platinum sheet as the counter electrode, Mg sample as the working electrode (0.785 cm² exposed area), and saturated calomel electrode (SCE) as the reference electrode was adopted. The volume of the electrolyte was 1000 mL, the electrolyte was 3.5% NaCl solution, the temperature was 23 ± 1 °C, and the experiment was conducted three times to improve the statistics. The polarization curves were acquired at a scanning rate of 5.0 mV/s from −500 to 400 mV with respect to the open circuit potential. The samples soaked in 3.5% NaCl for 24 h were observed by scanning electron microscopy (SEM, ZEISS SIGMA500, Dresden, Germany).

In order to calculate the electronic structure, the crystal structure of Mg₂C₃ was constructed by a first-principle calculation with the CASTEP module in the Materials Studio software [34]. The unit cell constant of Mg₂C₃ and each atomic lattice were completely relaxed until the unit cell energy converged to a fixed value before the calculation. The result of the calculation ignores the rotation effect.

3. Results and Discussion

Figure 1 displays the XPS depth profile of the ion-implanted AM60 alloy of Sample C3. A carbon-rich layer is formed after C ion implantation with a depth of about 250 nm. The high-resolution XPS spectra of C, O, Al, and Mg acquired after sputtering for different times are displayed in Figure 2. As the sputtering time increases, the C peak intensity decreases (Figure 2a) and the Mg intensity increases gradually (Figure 2d). The Al intensity also increases (Figure 2c), and O is observed at the sputtering times of 0 and 15 min (Figure 2b). The C binding energy is 284.5 eV (Figure 2a), suggesting a sp² hybridization composed of three σ bonds and one π bond perpendicular to the σ bond. This observation is consistent with previous results, and it is generally believed that sp² hybridization is formed by low-energy ion implantation [35,36].

Figure 3 shows the Raman scattering spectra. Before ion implantation, there is no C peak, but after C ion implantation, a G peak at 1542.14 cm⁻¹ and D peak at 1331.66 cm⁻¹ arising from amorphous carbon with sp² and sp³ hybridization appear, being consistent with the XPS data. Figure 4 shows the XRD patterns, and α-Mg and Mg₁₇Al₁₂ are present. A weak Mg₂C₃ phase was formed after ion implantation, especially for high fluences such as for Samples C2 and C3. Figure 5 shows the TEM images of Sample C3. Figure 5a shows that the carbon-implanted sample is about 250 nm thick, consistent with the results of XPS. The white line shows the interface between the C layer and substrate. The black objects are the compound formed during ion implantation. A typical compound is revealed in the near surface as shown in Figure 5b. Figure 5c is a higher magnification of part of the white circle area in Figure 5b. The distance of the lattice space of the compound is 0.37 nm. According to the EDS results, the percent of Mg is 34.6%, the percent of C is 61.3%, and the percent of O is 4.1%. The compound is mainly composed of Mg and C. The diffraction patterns of the compound are displayed in Figure 5d. The results of TEM and XRD suggest that the compound is Mg₂C₃.

According to Find It soft, Mg₂C₃ has a complex cubic structure. The Mg₂C₃ space group is Pnnm (parameter code 58), and a = 6.4108 Å, b = 5.2786 Å, and c = 3.7283 Å, as shown in Table 2. Based on the data, a unit cell model and the electron density map are shown in Figure 6a,b, respectively. Figure 6c shows the density of states (DOS) of the Mg₂C₃ unit cell, and the large peak shows two kinds of atomic p orbitals. The main electron energy is concentrated between −50 and −40 eV, and the electron energy mainly comes from Mg (p) and Mg (s). In addition, the valence electron of C (s) and C (p) makes a small contribution. The structure is primarily responsible for the improved corrosion resistance, to be discussed later.

Figure 7 presents the potentiodynamic polarization curves of the different samples in the 3.5% NaCl solution. The corrosion potential (E_corr) and corrosion current density (I_corr) are determined by Tafel extrapolation. If a tangent is made to the cathodic polarization curve and the anodic polarization curve, the ordinate of the intersection of the two lines and the E_corr potential line is the I_corr. Compared to that of the un-implanted AM60 control sample, the E_corr of Sample C3 shifts from −1.48 to −1.35 V, indicative of better corrosion resistance in the NaCl solution. The I_corr of sample C3 is 20.1 μA/cm², which is much lower than that of the AM60 control sample (50.6 μA/cm²). The more positive E_corr and smaller I_corr demonstrate that C ion implantation improves the corrosion resistance of the Mg alloy by forming the modified structure as described previously [37,38].

The morphology of the different samples after immersion in 3.5% NaCl is shown in Figure 8. Lots of corrosion defects are observed from the surfaces of the control samples (Figure 8a-2). The SEM images were obtained from the marked part in the black box of the digital picture. It can be seen that the corrosion area of sample BM is larger than that of the other samples. The EDS performed on Point 1 as shown in Figure 8d-2 indicates that there are Mg, O, and C elements on the surface after C ion implantation.

Figure 9 is the schematic presentation of the corrosion of the different samples. The inner layer is composed of AM60 alloy, and a thin layer of MgO is attached to the outer layer. The MgO layer on the surface is hydrated during exposure to an aqueous environment, which converts the MgO into a larger stable Mg(OH)₂ layer [24], and H₂ is produced in the corrosion process as shown in Figure 9a. The reaction may be expressed as the sum of the following reactions:

Mg = Mg²⁺ + 2e        (anodic reaction)

2H₂O + 2e = H₂ + 2(OH)⁻     (cathodic reaction)

Mg²⁺ + 2(OH)⁻ = Mg(OH)₂    (product formation)

Mg + 2H₂O = Mg(OH)₂ + H₂   (overall reaction)

The anodic reaction (Equation (1)) probably involves intermediate steps, which may produce the monovalent magnesium ion (Mg⁺), which has a short lifetime [39]. The reduction process for hydrogen ions and the hydrogen overvoltage of the cathodic phase play an important role in the corrosion of magnesium [40]. After C ion implantation, there is a C layer on the surface. The sample from C ion implantation gives rise to better corrosion resistance. Mg₂C₃ scattered in the C layer and C layer can decrease the corrosion and prevent corrosion from entering the substrate as shown in Figure 9b.

4. Conclusions

(1) A 250 nm-thick C-rich coating is formed on the surface of AM60 after C implantation with an ion implantation dose of 6 × 10¹⁶ ions/cm², and a Mg₂C₃ phase is observed from the ion-implanted region.

(2) The large peak in the density of states (DOS) shows the two atomic p orbitals of Mg₂C₃. The main electron energy is concentrated between −50 and −40 eV, and the electron energy mainly comes from Mg (p) and Mg (s).

(3) The more positive E_corr and smaller I_corr demonstrate that C ion implantation gives rise to better corrosion resistance in AM60 magnesium alloys.

Figure 1. XPS element depth profile of the AM60 alloy after C ion implantation at 6 × 106 ions/cm2 with a sputtering rate of 10 nm/min.

Figure 2. High-resolution XPS spectra of the treated AM60 alloy at 6 × 106 ions/cm2 after sputtering for different times: (a) C 1s, (b) O 1s, (c) Al 2p, and (d) Mg 1s.

Figure 3. Raman scattering spectra of the carbon films.

Figure 4. XRD patterns of different samples.

Figure 5. Cross-sectional TEM images of Sample C3: (a) surface microstructure, (b) compound microstructure, (c) high resolution TEM images, and (d) diffraction patterns of the compound.

Figure 6. First-principle study of Mg2C3: (a) unit cell model, (b) electron density map, and (c) state density maps.

Figure 7. Polarization curves of different samples.

Figure 8. Morphology of the corroded samples: (a) BM, (b) C1, (c) C2, and (d) C3; (i-1) low-magnification SEM pictures, and (i-2) high-magnification SEM pictures. EDS results acquired from Point 1 (i = a, b, c, and d).

Figure 9. A schematic presentation of the corrosion of different samples: (a) corrosion of AM60 Mg alloy, and (b) corrosion of AM60 with C nanolayer.

Samples	BM	C1	C2	C3
Fluence (ions/cm2)	0	1 × 1016	3 × 1016	6 × 1016

Crystal	Space Group	Lattice Parameters			Elements	Atomic Coordinates
		a	b	c		X	Y	Z
Mg2C3	58	6.4108	5.2786	3.7283	Mg(I)	0.2903	0.3901	0
					C(I)	0.5	0	0
					C(II)	0.6188	0.2070	0

Author Contributions

Conceptualization, J.D. and P.K.C.; methodology, J.D. and Z.L.; software, Z.L. and B.Y.; validation, B.Y.; formal analysis, Q.R.; investigation, Z.L.; resources, J.D.; data curation, B.Y. and Q.R.; writing-original draft preparation, Z.L. and B.Y.; writing-review and editing, J.D. and P.K.C.; visualization, J.D.; supervision, J.D. and P.K.C.; project administration, P.K.C.; funding acquisition, J.D. and P.K.C. All authors have read and agreed to the published version of the manuscript.

Funding

The research was financially supported by the postdoctoral research funding plan in Jiangsu province under Grant No. 2018K055C, Jiangsu Shuang-Chuang project and City University of Hong Kong Strategic Research Grants (SRG) Nos. 7005105 and 7005264.

Acknowledgments

The authors would like to thank Xin Tong of City University of Hong Kong for providing assistance in the ion implantation experiments.

Conflicts of Interest

There are no conflicts of interest to declare.

References

1. Staiger, M.P.; Pietak, A.M.; Huadmai, J.; Dias, G. Magnesium and its alloys as orthopedic biomaterials: A review. Biomaterials 2006, 27, 1728-1734.

2. Gray, J.E.; Luan, B. Protective coatings on magnesium and its alloys-A critical review. J. Alloys Compd. 2002, 336, 88-113.

3. Rahmati, M.; Raeissi, K.; Toroghinejad, M.R. Effect of pulse current mode on microstructure, composition and corrosion performance of the coatings produced by plasma electrolytic oxidation on AZ31 Mg alloy. Coatings 2019, 9, 688.

4. Hagihara, K.; Li, Z.X.; Yamasaki, M.; Kawamura, Y.; Nakano, T. Strengthening mechanisms acting in extruded Mg-based long-period stacking ordered (LPSO)-phase alloys. Acta Mater. 2019, 163, 226-239.

5. Chen, M.S.; Yuan, W.Q.; Li, H.B.; Zou, Z.H. New insights on the relationship between flow stress softening and dynamic recrystallization behavior of magnesium alloy AZ31B. Mater. Charact. 2019, 147, 173-183.

6. Johnston, S.; Shi, Z.M.; Atrens, A. The influence of pH on the corrosion rate of high-purity Mg, AZ91 and ZE41 in bicarbonate buffered Hanks' solution. Corros. Sci. 2015, 101, 182-192.

7. Song, D.; Li, C.; Liang, N.N.; Yang, F.L.; Jiang, J.H.; Sun, J.P.; Wu, G.S.; Ma, A.; Ma, X.L. Simultaneously improving corrosion resistance and mechanical properties of a magnesium alloy via equal-channel angular pressing and post water annealing. Mater. Des. 2019, 166, 107621.

8. Jian, S.Y.; Ho, M.L.; Shih, B.C. Evaluation of the corrosion resistance and cytocompatibility of a bioactive micro-arc oxidation coating on AZ31 Mg alloy. Coatings 2019, 9, 396.

9. Guo, H.F.; An, M.Z. Growth of ceramic coatings on AZ91D magnesium alloys by micro-arc oxidation in aluminate-fluoride solutions and evaluation of corrosion resistance. Appl. Surf. Sci. 2005, 246, 229-238.

10. Subramanian, R.; Sircar, S.; Mazumder, J. Laser cladding of Zirconium on magnesium for improved corrosion properties. J. Mater. Sci. 1991, 26, 951-956.

11. Volovitch, P.; Masse, J.E.; Fabre, A.; Barrallier, L.; Saikaly, W. Microstructure and corrosion resistance of magnesium alloy ZE41 with laser surface cladding by Al-Si powder. Surf. Coat. Technol. 2008, 202, 4901-4914.

12. Wu, G.S.; Jamesh, M.I.; Chu, P.K. Surface design of biodegradable magnesium alloys-A review. Surf. Coat. Technol. 2013, 233, 2-12.

13. Zheng, Y.; Zhang, L.B.; Bi, Y.Z. Corrosion behavior of Fe/Zr composite coating on ZK60 Mg alloy by Ion implantation and deposition. Coatings 2018, 8, 261.

14. Jin, W.H.; Wu, G.S.; Feng, H.Q.; Wang, W.H.; Zhang, X.M.; Chu, P.K. Improvement of corrosion resistance and biocompatibility of rare-earth WE43 magnesium alloy by neodymium self-ion implantation. Corros. Sci. 2015, 94, 142-155.

15. Feliu, S.; Maffiotte, C.; Samaniego, A.; Galvan, J.C.; Barranco, V. Effect of the chemistry and structure of the native oxide surface film on the corrosion properties of commercial AZ31 and AZ61 alloys. Appl. Surf. Sci. 2011, 257, 8558-8568.

16. Wan, Y.Z.; Xiong, G.Y.; Luo, H.L.; He, F.; Huang, Y.; Wang, Y.L. Influence of zinc ion implantation on surface nanomechanical performance and corrosion resistance of biomedical magnesium-calcium alloys. Appl. Surf. Sci. 2008, 254, 5514-5516.

17. Liu, H.X.; Xu, Q.; Jiang, Y.H.; Wang, C.Q.; Zhang, X.W. Corrosion resistance and mechanical property of AZ31 magnesium alloy by N/Ti duplex ion implantation. Surf. Coat. Technol. 2013, 228, S538-S543.

18. Wu, G.S.; Ding, K.J.; Zeng, X.Q.; Wang, X.M.; Yao, S.S. Improving corrosion resistance of titanium-coated magnesium alloy by modifying surface characteristics of magnesium alloy prior to titanium coating deposition. Scr. Mater. 2009, 61, 269-272.

19. Xie, Z.W.; Chen, Q.; Chen, T.; Gao, X.; Yu, X.G.; Song, H.; Feng, Y.J. Microstructure and properties of nitrogen ion implantation/AlN/CrAlN/MoS2-phenolic resin duplex coatings on magnesium alloys. Mater. Chem. Phys. 2015, 160, 212-220.

20. Zhu, X.M.; Yang, H.G.; Lei, M.K. Corrosion resistance of Al ion implanted AZ31 magnesium alloy at elevated temperature. Surf. Coat. Technol. 2007, 201, 6663-6666.

21. Jamesh, M.I.; Wu, G.S.; Zhao, Y.; Jin, W.H.; McKenzie, D.R.; Bilek, M.M.; Chu, P.K. Effects of zirconium and nitrogen plasma immersion ion implantation on the electrochemical corrosion behavior of Mg-Y-RE alloy in simulated body fluid and cell culture medium. Corros. Sci. 2014, 86, 239-251.

22. Jamesh, M.I.; Wu, G.S.; Zhao, Y.; Jin, W.H.; McKenzie, D.R.; Bilek, M.M.; Chu, P.K. Effects of zirconium and oxygen plasma ion implantation on the corrosion behavior of ZK60 Mg alloy in simulated body fluids. Corros. Sci. 2014, 82, 7-26.

23. Staišiunas, L.; Miečinskas, P.; Leinartas, K.; Selskis, A.; Grigucevičienė, A.; Juzeliunas, E. Sputter-deposited Mg-Al-Zn-Cr alloys-Electrochemical characterization of single films and multilayer protection of AZ31magnesium alloy. Corros. Sci. 2014, 80, 487-493.

24. Xu, R.Z.; Wu, G.S.; Yang, X.B.; Zhang, X.M.; Wu, Z.W.; Sun, G.Y.; Li, G.Y.; Chu, P.K. Corrosion behavior of chromium and oxygen plasma-modified magnesium in sulfate solution and simulated body fluid. Appl. Surf. Sci. 2012, 258, 8273-8278.

25. Wu, G.S.; Zhang, X.M.; Zhao, Y.; Jamesh, M.I.; Yuan, G.Y.; Chu, P.K. Plasma modified Mg-Nd-Zn-Zr alloy with enhanced surface corrosion resistance. Corros. Sci. 2014, 78, 121-129.

26. Höche, D.; Blawert, C.; Cavellier, M.; Busardo, D.; Gloriant, T. Magnesium nitride phase formation by means of ion beam implantation technique. Appl. Surf. Sci. 2011, 257, 5626-5633.

27. Li, Z.C.; Shang, Z.Z.; Wei, X.; Zhao, Q. Corrosion resistance and cytotoxicity of AZ31 magnesium alloy with N+ ion implantation. Mater. Technol. 2019, 34, 730-736.

28. Jamesh, M.I.; Wu, G.S.; Zhao, Y.; Chu, P.K. Effects of silicon plasma ion implantation on electrochemical corrosion behavior of biodegradable Mg-Y-RE Alloy. Corros. Sci. 2013, 69, 158-163.

29. Zhao, Y.; Jamesh, M.I.; Li, W.K.; Wu, G.S.; Wang, C.X.; Zheng, Y.F.; Yeung, K.W.K.; Chu, P.K. Enhanced antimicrobial properties, cytocompatibility, and corrosion resistance of plasma-modified biodegradable magnesium alloys. Acta Biomater. 2014, 10, 544-556.

30. Burlaka, L.; Kutsenko, L.; Talianker, M.; Fuks, D.; Kiv, A.; Brown, I. Observation of ε-Ag17 Mg54 phase induced by plasma immersion ion implantation. Radiat. Eff. Defect. S. 2013, 168, 631-635.

31. Xu, R.Z.; Yang, X.B.; Li, P.H.; Suen, K.W.; Wu, S.; Chu, P.K. Eelectrochemical properties and corrosion resistance of carbon-ion-implanted magnesium. Corros. Sci. 2014, 82, 173-179.

32. Marpaung, F.; Park, T.; Kim, M.; Yi, J.W.; Lin, J.J.; Wang, J.; Ding, B.; Lim, H.; Konstantinov, K.; Yamauchi, Y. Gram-Scale Synthesis of Bimetallic ZIFs and Their Thermal Conversion to Nanoporous Carbon Materials. Nanomaterials 2019, 9, 1796.

33. Song, H.; Chen, G.; Chen, J.; Li, H.X.; Ji, L.; Jiang, N. Improving the Wear Life of a-C:H Film in High Vacuum by Self-Assembled Reduced Graphene Oxide Layers. Nanomaterials 2019, 9, 1733.

34. Zhang, Y.; Guo, D.; Geng, H. Characterization of M-class genome segments of muscovy duck reovirus S14. Virus Res. 2007, 125, 42-53.

35. Chu, P.K.; Chen, J.Y.; Wang, L.P.; Huang, N. Plasma-surface modification of biomaterials. Mater. Sci. Eng. R 2002, 36, 143-206.

36. Zou, Y.S.; Wu, Y.F.; Yang, H.; Cang, K.; Song, G.H.; Li, Z.X.; Zhou, K. The microstructure, mechanical and friction properties of protective diamond like carbon films on magnesium alloy. Appl. Surf. Sci. 2011, 258, 1624-1629.

37. Toorani, M.; Aliofkhazraei, M.; Rouhaghdam, A.S. Microstructural, protective, inhibitory and semiconducting properties of PEO coatings containing CeO2 nanoparticles formed on AZ31 Mg alloy. Surf. Coat. Technol. 2018, 352, 561-580.

38. Toorani, M.; Aliofkhazraei, M. Review of electrochemical properties of hybrid coating systems on Mg with plasma electrolytic oxidation process as pretreatment. Surf. Interfaces 2019, 14, 262-295.

39. Makar, G.L.; Kruger, J. Corrosion studies of rapidly solidified magnesium alloys. J. Electrochem. Soc. 1990, 137, 414-421.

40. Song, G.L.; Atrens, A. Corrosion Mechanisms of Magnesium Alloys. Adv. Eng. Mater. 1999, 1, 11-33.