Severe corrosion behavior of Fe78Si9B13 glassy alloy under magnetic field

Journal of Non-Crystalline Solids 392–393 (2014) 51–58

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Severe corrosion behavior of Fe78Si9B13 glassy alloy under magnetic field Y.J. Li a, B. An a, Y.G. Wang a, Y. Liu a, H.D. Zhang a, X.G. Yang b, W.M. Wang a,⁎ a b

Key Laboratory for Liquid–Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan 250061, China Institute for Fluid Dynamics, Technische Universitaet Dresden, 01069 Dresden, Germany

a r t i c l e

i n f o

Article history: Received 21 December 2013 Received in revised form 4 March 2014 Keywords: Metallic glass; Magnetic field; Corrosion; EIS; XPS

a b s t r a c t The corrosion behavior of Fe78Si9B13 glassy ribbons in 0.3 M NaCl + 0.06 M NaOH solution under magnetic field has been studied by immersion and electrochemical tests such as electrochemical impedance spectroscopy (EIS) technique and polarization scanning, and the corroded morphology and products of ribbons have been measured by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS). It is found that the added magnetic field induces a severe corrosion behavior of the Fe-based glassy ribbons despite being in immersion or electrochemical corrosion, reflecting in a larger corrosion rate and a lower pitting potential. In addition, the magnetic field can decrease the charge transfer resistance (Rt) in the equivalent circuit of the electrochemical reaction, can trigger the occurrence of filiform corrosion and cracks, and can hinder the formation of silicon dioxide on the sample surface. The severe electrochemical corrosion of Fe-based glass alloy under magnetic field is explained by the effects of magnetohydrodynamic (MHD). © 2014 Elsevier B.V. All rights reserved.

1. Introduction Fe-based amorphous alloys are particularly interesting and different from the corresponding crystalline alloys due to their high glass-forming ability, ultrahigh strength and hardness, soft magnetic properties, good corrosion and wear resistance [1–4]. The Fe78Si9B13 glassy ribbon has an important position in the industry due to its various properties. For instance, it can be used in magnetic sensor and power transformer etc. [5,6]. Because these equipments are often working under magnetic field and installed outdoors, the study about the effect of magnetic field on the corrosion resistance of Fe78Si9B13 glassy ribbon is necessary. A lot of investigations about the effect of magnetic field on the corrosion behavior of metals have been reported in the literature. Costa et al. [7] has found that magnetic field can increase the corrosion rate of Nd–Fe–B permanent magnetic in 3.5 wt.% sodium chloride solution. The corrosion rate of some materials such as titanium, austenitic and martensitic steels is also increased under magnetic field [8,9]. The superimposed magnetic field can affect the electrochemical corrosion of metallic materials in aqueous solutions by two mechanisms: the influence on the charge transfer step and on the mass transfer step in electrolyte [10]. For the impact of an applied uniform magnetic field on mass transfer step, it has been explained by the

⁎ Corresponding author. Tel.: +86 531 88392749; fax: +86 531 88395011. E-mail address: [email protected] (W.M. Wang).

http://dx.doi.org/10.1016/j.jnoncrysol.2014.03.030 0022-3093/© 2014 Elsevier B.V. All rights reserved.

magnetohydrodynamic (MHD) theory, i.e. mainly attributed to the introduction of Lorentz force on the ions in the electrolyte under magnetic field [11,12]. The Lorentz force can cause a stirring of the electrolyte by accelerating charges moving in the direction perpendicular to the current and the flux density. It has been reported that the MHD convection can reduce the thickness of diffusion layer and concentration polarization, and consequently enhances the mass transport process [13–16]. And the application of magnetic field to the electrochemical cell can lead to a mixed diffusion-convection mass transport process [17]. Several studies have been reported that the magnetic field can affect the electrochemical process of pure Fe in aqueous solution by enhancing mass transport [18,19]. However, the influence of an applied magnetic field on charge transfer step has been controversial. Many studies have indicated that there is no significant influence of magnetic field on the process controlled by charge transfer step [20–22]. But Sueptitz et al. [10] and Lu and Yang [23] have reported that the magnetic field can affect chargetransfer process of electrochemical corrosion of pure Fe in acidic solutions. Hinds et al. [24] have argued that the charge transfer resistance depends on the exchange current density, the change of which under a magnetic field may be an indirect mass transport effect. However, there is little work involving the effect of magnetic field on the corrosion system in alkaline solution. Hence, investigating the effect of magnetic field on the charge transfer step in alkaline solution is valuable. Electrochemical impedance spectroscopy (EIS) is a common and powerful tool to characterize the corrosion resistance of various materials [25–30]. The measured Nyquist plots can be fitted to an appropriate equivalent circuit which provides the important properties of anodized

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Corrosion rate, R (g· m-2· h-1)

Table 1 Atomic concentration of the elements on surfaces of Fe78Si9B13 glassy ribbons analyzed by EDS after immersion corroded.

0T 0.2 T

0.08 0.07 0.06

Magnetic field

Position

Fe (at.%)

Si (at.%)

B (at.%)

O (at.%)

0T 0.2 T

Flake Film

16.7 46.6

0.8 6.0

24.9 16.1

57.7 12.7

0.05 0.04 0.03 quantitative analysis of the ribbon after corroded, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy dispersive spectrometer (EDS) have been used in this paper.

0.02 0.01 0.00 1

2

3

2. Experimental procedure

T (week) Fig. 1. The corrosion rates of Fe78Si9B13 glassy ribbons in 0.3 M NaCl + 0.06 M NaOH solution without and with magnetic field at 298 K open to air.

surface layers such as the capacitance, solution resistance and charge transfer resistance [31]. However, to the author's knowledge, the effect of magnetic field on the EIS analysis of the glassy alloys has not been reported so far. The main objective of this study is to find the effect of magnetic field on corrosion of Fe78Si9B13 glassy ribbon in 0.3 M NaCl + 0.6 M NaOH in immersion corrosion and electrochemical test. For qualitative and

(a) 0 T

The Fe78Si9B13 glassy ribbons were supplied by Qingdao Yunlu Energy Technology Co. Ltd. The X-ray diffraction analysis shows that the sample is in fully amorphous state, which is not shown here. The size of the commercial ribbons we used was 40 mm in width, 35 μm in thickness and about 20,000 mm in length and we cut the ribbon in the size of 3 × 40 mm for corrosion tests. Before all the tests, the ribbons were polished with metallographic sandpaper of 1200 grain size. Immersion experiments were carried out on the samples first. The glassy ribbons were immersed in 0.3 M NaCl + 0.06 M NaOH solution open to air at room temperature (about 298 K). A uniform 0.2 T magnetic field has been superimposed on the immersion sample. The corrosion rates were evaluated from the weight change of samples after immersion for 1, 2 and 3 weeks.

(b) 0 T

P

10 µm

2 µm

(c) 0.2 T

(d) 0.2 T

F

10µm 10 µm

2 µm

Fig. 2. SEM micrographs of immersion corroded surfaces of Fe78Si9B13 glassy ribbons in 0.3 M NaCl + 0.06 M NaOH solution for one week without and with magnetic field. The positions used for energy spectrum collection are shown on the images. F—Film, P—Particle.

Y.J. Li et al. / Journal of Non-Crystalline Solids 392–393 (2014) 51–58

(a) Fe 2p

(b) Si 2p

Fe 2p3/2

Fe 2p1/2

53

SiOx

0T

SiO2

Si

740

SiOx

3000 cps

0.2 T

730

720

SiO2

Si

200 cps

Fe 2p3/2

Fe 2p1/2

Intensity

Intensity

0T

0.2 T

710

108

106

Binding Energy (ev)

104

102

100

98

96

Binding Energy (eV)

(c) O 1s FexOy

Fe(OH)3

SiO2

Intensity

0T

Fe(OH)3

4000 cps

FexOy

SiO2

0.2 T 540

536

532

528

524

Binding Energy (eV) Fig. 3. XPS spectra of: (a) Fe 2p, (b) Si 2p and (c) O 1s recorded from the surface of Fe78Si9B13 glassy ribbons after immersion corroded in 0.3 M NaCl + 0.06 M NaOH solution for one week without and with magnetic field.

Electrochemical measurements were carried out using a typical three-electrode system: working electrode, platinum counter electrode and Hg/HgO reference electrode. ACM Instruments was used for the electrochemical impedance spectroscopy (EIS) measurements at room temperature after a 20 min exposure to the test solution. Thus, it made all the samples get a stationary open-circuit potential before the test. The EIS method was used in the frequency range from 105 to 0.05 Hz and involved the imposition of a sine wave with 5 mV in amplitude. LK2005A advanced electrochemical workstation was used for measuring the polarization curves with a scan rate of 5 mV/s. In the whole process of electrochemical experiment, we kept the wheel side of the ribbon opposite to the platinum electrode. In order to verify the impact of magnetic field on the electrochemical corrosion of the Fe-based glassy ribbon, we also measured the polarization curves of the single-faced ribbons (only the wheel side) with CHI 660 E electrochemical workstation with a scan rate of 5 mV/s. When we superimposed 0.2 T magnetic field during electrochemical measurements, electrolytic cell was placed in the center between the magnets and the current direction was perpendicular to the magnetic field direction. The test solution, 0.3 M NaCl + 0.06 M NaOH solution,

was prepared with analytical grade NaCl and NaOH reagents and deionized water. The surface morphologies of the ribbons after immersion and electrochemical tests were examined using scanning electron microscopy (SEM, SU-70). The composition of the corrosion products was analyzed by energy dispersive spectroscopy (EDS). The surface film was also analyzed by X-ray photoelectron spectroscopy (XPS, ESCALAB 250Xi) performed on a photoelectron spectrometer with AlKα excitation. All the analyses were made for the wheel side of the double-faced ribbons. 3. Results and discussion 3.1. Immersion test Fig. 1 shows the average corrosion rates of Fe78Si9B13 glassy ribbon in 0.3 M NaCl + 0.06 M NaOH solution without and with 0.2 T magnetic field after immersion for 1, 2 and 3 weeks. Without magnetic field, the corrosion rate of the ribbon increases linearly with the immersion time; while with 0.2 T magnetic field, the ribbon's corrosion rate has no obvious change in the first two weeks and shows an apparent

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-1

(a)

(a)

30000

0T 0.2 T

-2

Log i (A cm-2)

Z'' (ohm cm2)

25000 0 T Measured 0 T Simulated 0.2 T Measured 0.2 T Simulated

20000 15000

-3 -4 -5

Epit

-6

10000

with LK2005A

-7

Ecorr

5000 -8 -1.5

0 0

5000

10000

15000

20000

25000

-1.0

-0.5

0.5

Potential, E (V, Hg/HgO)

Z' (ohm cm2)

-1

(b)

(b)

0.0

0T 0.2 T

-2

Cdl

-3

Log i (A cm-2)

Rs

Rt

-4 -5 Epit

-6

Fig. 4. Experimental Nyquist plots and the equivalent circuit of Fe78Si9B13 glassy ribbons in 0.3 M NaCl + 0.06 M NaOH solution without and with magnetic field after holding the samples at open-circuit potential for 20 min.

with CHI660E

-7 -8 -1.5

Ecorr

-1.0

-0.5

0.0

0.5

Potential, E (V, Hg/HgO) increment in the last week. In general, the corrosion rate with 0.2 T magnetic field is much larger than that without magnetic field. In other words, the magnetic field induces a severer corrosion of Febased glassy ribbon. In the ribbon, iron is solvent component, and can react with oxygen in alkaline solution. The corresponding equilibrium reactions are [32] 2Fe þ O2 þ 2H2 O ¼ 2FeðOHÞ2

ð1Þ

4FeðOHÞ2 þ O2 þ 2H2 O ¼ 4FeðOHÞ3 :

ð2Þ

It is known that oxygen molecules are paramagenic [33], their transport towards the specimen must be affected by the magnetic field. As shown in earlier work, the magnetic field reacts with the electric field created by the corrosion cells [34]. This reaction on ribbon can be explained by magneto-hydrodynamic (MHD) flow. The MHD convection can enhance the mass transporting process. In addition, Costa et al. [7] have supposed that the transportation of oxygen to the specimen is facilitated in the presence of the magnetic field, leading to an increased

Table 2 Electrochemical parameters obtained from EIS spectra for Fe78Si9B13 glassy ribbons in 0.3 M NaCl + 0.06 M NaOH solution without and with magnetic field. Magnetic field

Rs (Ω cm2)

Rt (kΩ cm2)

Cdl (μF cm−2)

0T 0.2 T

38.9 34.9

52.4 8.9

18.2 32.3

Fig. 5. (a) Potentiodynamic polarization curves of Fe78Si9B13 glassy ribbons with double faces in 0.3 M NaCl + 0.06 M NaOH solution without and with magnetic field. (b) For comparison, the sample with single face is measured with CHI660E in the same condition.

supply of these oxidizing species to the interface and consequently an acceleration of the corrosion progress. To better understand the difference in corrosion resistance of Fe78Si9B13 glassy ribbons without and with magnetic field, the surfaces of the specimens after immersion in 0.3 M NaCl + 0.06 M NaOH solution for 1 week were examined by SEM, as shown in Fig. 2. After immersion without magnetic field, a lot of white flake-like products present on the surface of the ribbon, which distribute densely and form a protective layer on the sample surface, and the diameter and thickness of which are about 5 and 0.5 μm, respectively (Fig. 2a and b). After immersion with 0.2 T magnetic field, there are also white flake-like products on the ribbon surface, but their number is much fewer and their size (2 μm in diameter, 0.1 μm in thickness) is much smaller compared with the counterpart with 0 T (Fig. 2c and d). In addition, there are some holes with a diameter up to 10 μm on the ribbon after immersion under 0.2 T magnetic field. The element contents by EDS analysis on two samples are listed in Table 1. We consider that the flake on the ribbon with magnetic field is the same phase as that without magnetic field. The O content of the flake in the ribbon is higher than that of the film, indicating that the flake is mainly oxide. The content ratio of silicon to iron of the flake is lower than that of the film, indicating that the iron oxide on the sample surface grows quicker than the silicon oxide and covers on them during immersion with 0 T. Both because of more oxides formed on the ribbon immersed in 0 T magnetic field and because of a

Y.J. Li et al. / Journal of Non-Crystalline Solids 392–393 (2014) 51–58

(a) 0 T

55

(b) 0 T

F

10 µm

2 µm

(c) 0.2 T

(d) 0.2 T

10 µm

2 µm

P

F

Fig. 6. SEM micrographs of electrochemical corroded surfaces of Fe78Si9B13 glassy ribbons in 0.3 M NaCl + 0.06 M NaOH solution without and with magnetic field. The positions used for energy spectrum collection are shown on the images. F—Film, P—Particle.

larger area of fresh surface to join the oxidation reaction in the ribbon with 0.2 T (Fig. 2), it is expected that the ribbon has a lower corrosion rate with 0 T. Fig. 3 shows the X-ray photoelectron spectroscopy (XPS) spectra of Fe 2p, Si 2p and O 1s recorded from the surfaces of Fe-based glassy ribbons after immersion for 1 week with 0 and 0.2 T magnetic field. The shape of Fe 2p and Si 2p curves of the ribbon with 0 T is similar to that with 0.2 T (Fig. 3a and b). The XPS spectrum of Si 2p can be decomposed into three peeks: Si, SiOx and SiO2 [35]. After immersion with 0.2 T magnetic field, the area of Si peak increases, while the areas of SiOx and SiO2 decrease. According to earlier works [36,37], the O 1s spectrum can be decomposed into three peaks belonging to metal oxide species FexOy (Fe3O4, Fe2O3, etc.), the hydroxide species Fe(OH)3 and SiO2 (Fig. 3c). The area of SiO2 peak of the sample with 0 T is significantly larger than that with 0.2 T magnetic field, being consistent with the decomposition result in the spectrum of Si 2p. Also, the total peak area of O 1s spectrum of the sample with 0 T is larger than that with 0.2 T, indicating that more oxides have presented on surface. This result is consistent with the former SEM (Fig. 2) and EDS analysis (Table 1). 3.2. Electrochemical test Fig. 4 displays the impedance data of Fe78Si9B13 glassy ribbon in 0.3 M NaCl + 0.06 M NaOH solution with 0 and 0.2 T magnetic field at room temperature. The Nyquist plots of both samples present only one capacitive loop, reflecting one single time constant in the electrochemical test (Fig. 4a). The semicircle diameter in Nyquist plots decreases with adding the magnetic field, indicating that the charge transfer resistance is decreased. In order to fit the impedance spectra, an appropriate equivalent circuit to describe the electrochemical reaction is shown in Fig. 4b. It contains the following elements: the solution resistance (Rs), the double layer capacitance (Cdl), and the charge transfer resistance (Rt), which are

collected in Table 2. With superimposing 0.2 T magnetic field in the experiment, the value of Rt decreases obviously. Hu et al. [38] have reported that the magnetic field can accelerate the charge transfer rate, reflecting in the smaller charge transfer resistance (Rt). At the same time, it has been found that the charge transfer resistance is reduced by the magnetic field [39]. A larger Rt means a higher corrosion resistance [40]. Thus it is expected that the sample with magnetic field has a larger corrosion rate than that without magnetic field (Fig. 1). The typical potentiodynamic polarization curves of Fe78Si9B13 glassy ribbons with double faces and single face, obtained in 0.3 M NaCl + 0.06 M NaOH solution with 0 and 0.2 T magnetic field, are shown in Fig. 5. For the double-faced ribbons in Fig. 5a, each curve has an obvious current plateau which is associated with the passive film formation during the anodic polarization. At relatively low potentials, active dissolution of metals and formation of low valence oxide occur. Generally, the hydroligand MOHads (M represents a metal) is considered as the precursor in the dissolution process and the interface/interphase film development process. The large passive current density indicates the formation and dissolution of Fe(OH)2 and Fe(OH)3, which finally transform to Fe2O3 [41]. The polarization curves with and without magnetic field do not reflect the strong difference in the resistance values that was measured by EIS, this is may due to the different instruments and lengths of testing

Table 3 Atomic concentration of the elements on surfaces of Fe78Si9B13 glassy ribbons analyzed by EDS after electrochemical corroded. Magnetic field

Position

Fe (at.%)

Si (at.%)

B (at.%)

O (at.%)

0T 0.2 T

Film Film Particle

81.8 80.1 27.5

10.3 10.3 2.8

0 0.5 0.8

7.9 9.1 68.9

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(b) Si 2p

(a) Fe 2p Fe 2p3/2

Fe 2p1/2

0T

SiOx SiO2

SiOx Si

SiO2

0.2 T

740

730

720

710

108

106

Binding energy (eV)

104

102

100

98

300 cps

Intensity

2000 cps

Intensity

Fe 2p3/2

Fe 2p1/2

0.2 T

Si

0T

Fe

96

Binding energy (eV)

(c) O 1s Fe(OH)3

FexOy

SiO2

Fe(OH)3

FexOy

SiO2

0.2 T

540

536

532

528

3000 cps

Intensity

0T

524

Binding Energy (eV) Fig. 7. XPS spectra of (a) Fe 2p, (b) Si 2p and (c) O 1s recorded from the surface of Fe78Si9B13 glassy ribbons after electrochemical corroded in 0.3 M NaCl + 0.06 M NaOH solution without and with magnetic field.

time. But the difference in the value of pitting potential Epit between the samples with 0 and 0.2 T is obvious. The sample with 0.2 T magnetic field needs a smaller potential to impel the occurrence of pitting corrosion. The Epit errors (ΔEpit) of ribbons with 0 and 0.2 T are 0.024 V and 0.014 V and the standard deviations are 0.012 V and 0.007 V, respectively. The effect of magnetic field on pitting potential is also found for the single-faced ribbons in Fig. 5b. According to the magnetohydrodynamic (MHD) effect [13–16], the magnetic field can promote the dissolution of passivation film, thus promote the occurrence of pitting corrosion. In

addition, Lu et al. [41,42] have reported that the magnetic field and Cl− have a synergistic effect on the destruction of the passive film. The chlorides have a more harmful effect on the breakdown of steady passive film and cause the passive film to be precipitation–dissolution type. The dissolution rate of precipitation–dissolution type film is controlled by the mass transfer rate at the film/solution interface, which is affected by applied magnetic field. Fig. 6 gives SEM micrographs of corroded surfaces of Fe-based glassy ribbons after potentiodynamic polarization (Fig. 5a) in 0.3 M NaCl +

Table 4 The fraction of decomposed peaks from XPS spectra of Si 2P together with total area of sample surfaces after corroded in 0.3 M NaCl + 0.06 M NaOH solution.

Table 5 The fraction of decomposed peaks from XPS spectra of O 1s as well as total area of sample surfaces after corroded in 0.3 M NaCl + 0.06 M NaOH solution.

Corrosion method

Magnetic field

Si (%)

SiOx (%)

SiO2 (%)

Total area

Corrosion method

Magnetic field

SiO2 (%)

Fe(OH)3 (%)

FexOy (%)

Total area

Immersion

0T 0.2 T 0T 0.2 T

22.8 35.7 15.5 35.3

74.5 62.2 56.0 46.6

2.7 2.1 28.5 18.1

1300 1153 1753 678

Immersion

0T 0.2 T 0T 0.2 T

17.8 5.9 28.5 20.0

50.5 71.1 60.0 54.9

31.7 23.0 11.5 25.1

26,122 21,542 18,264 12,764

Electrochemical

Electrochemical

Y.J. Li et al. / Journal of Non-Crystalline Solids 392–393 (2014) 51–58

0.06 M NaOH solution with 0 and 0.2 T magnetic field. With 0 T, the outline of original gullies does not change drastically and there are only some pits in size of 0.1 μm on the surface of the ribbon after electrochemical corrosion, as well as white particles in size of less than 100 nm (Fig. 6a and b). With 0.2 T, there are also white particles of less than 100 nm distributing widely on the matrix surface, the number of which is lower than that with 0 T. This phenomenon is similar to the immersed samples (Fig. 2). Meanwhile, the pits in size of 5–20 μm are much larger than those with 0 T, and they connect to form some filaments with many cracks on the ribbon surface (Fig. 6c). According to the previous works [43,44], this is considered as a type of filiform corrosion. It has been reported that filament propagation starts from corrosion pits and occurs due to a strong corrosion reaction under hydrogen evolution at the filament head and outside the filaments [44,45]. Meanwhile, for mild steel API P110, the filiform corrosion occurs during immersion in Soultz geothermal brine, which is ascribed to the electrochemical heterogeneity [46]. Eliaz and Eliezer [47] have reported that Fe–Si–B amorphous alloy can adsorb hydrogen due to its inherent atomic-scale stress, eventually initiate a crack at the surface. To authors' knowledge, there is no study giving a filiform corrosion phenomenon for an amorphous Fe-based alloy in alkaline solution. Therefore, the reason for filiform corrosion phenomenon and mechanism underlying electrode reactions in alkaline environment needs further research. The element contents by EDS analysis on the samples after electrochemical corrosion are shown in Table 3. With 0.2 T magnetic field, the O content of the large oxidation products with the crack is much higher compared with the film, and the Si content of the large products is lower, indicating that the large products with the cracks contain more iron oxide and less silicon oxide. It is known that the Fe–Si–B amorphous alloy can supply silicon to build up a thin layer protective film of SiO2 on the entire alloy surface and iron oxide nucleates and grows within the SiO2 film [48]. From the relatively less silicon oxide and more iron oxide around the crack of sample with 0.2 T, it can be inferred that the magnetic field enhances the formation of the unprotective iron oxide and induces the stress, thus promotes the cracking of protective silicon oxide film and results in a server corrosion with 0.2 T magnetic field. In addition, XPS measurements have been performed to analyze elements on the sample surface after electrochemical corrosion, as shown in Fig. 7. From the spectra of Fe 2p, we can see that the sample after electrochemical corrosion without magnetic field has a noticeable peak at around 706.7 eV (Fig. 7a), which refers to free Fe [49]. This phenomenon indicates that the ribbon corroded with 0 T has a thinner passive film and the X-ray can penetrate it and hit the matrix directly. Then the pitting formed on the ribbon surface can also make the matrix leakage. As mentioned above, the Si 2P peak can be decomposed into three peaks: Si, SiOx and SiO2 (Fig. 7b). The fractions of three peaks are shown in Table 4, as well as the Si 2p decomposition result of samples after immersion. The total area of Si 2P of the ribbon after being corroded with 0 T magnetic field is much larger than that with 0.2 T, indicating that there exist more Si atoms or oxides on the surface with 0 T. Moreover, the percentage of SiO2 of the sample with 0 T is larger than that with 0.2 T after both immersion and electrochemical tests. In the XPS spectra of O 1s, the O binding energy of the sample after corroded with 0.2 T has a lower value than that with 0 T (Fig. 7c). Both O 1s curves are decomposed into three peaks: oxide metal species FexOy (Fe3O4, Fe2O3, etc.), the hydroxide species Fe(OH)3 and SiO2. The fractions of three parts are shown in Table 5 as well as the decomposition result of O 1s for samples after immersion. The ribbon after being corroded without magnetic field has a higher percentage of intermediate product Fe(OH)3 and a lower percentage of final product FexOy compared with the ribbon with 0.2 T, indicating that its corrosion process is slower. In addition, the SiO2 percentage of the ribbons with 0 T is larger than that with 0.2 T after both immersion and electrochemical tests, which is consistent with the decomposition result of Si 2P in Table 4.

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The larger SiO2 percentage of the sample with 0 T indicates that its protective film of SiO2 is thicker or denser than that with 0.2 T. In a word, the magnetic field can hinder the formation of SiO2, and thus promote the corrosion of Fe78Si9B13 glassy ribbon. 4. Conclusions The influence of magnetic field on the corrosion behavior of Fe78Si9B13 glassy alloy has been investigated by various technical means, several conclusions can be drawn as follows: (1) Magnetic field can accelerate the corrosion process of Febased glassy ribbon, despite being in immersion test or in electrochemical test. (2) In electrochemical test, the added magnetic field reduces the charge transfer resistance (Rt) and triggers the occurrence of filiform corrosion and cracks. (3) From XPS spectra of the samples after immersion and electrochemical corrosion, it can be inferred that the magnetic field can hinder the formation of the protective film of SiO2, thus promote the corrosion of the ribbon. Acknowledgments The authors acknowledge the National Natural Science Foundation of China (No. 51171091), the Excellent Youth Project of Shandong Natural Science Foundation (No. JQ201012) and the National Basic Research Program of China (973 Program) (No. 2012CB825702). References [1] C.T. Chang, T. Kubota, A. Makino, A. Inoue, J. Alloys Compd. 473 (2009) 368–372. [2] Z.L. Long, C.T. Chang, Y.H. Ding, Y. Shao, P. Zhang, B.L. Shen, A. Inoue, J. Non-Cryst. Solids 354 (2008) 4609–4613. [3] A. Basu, A.N. Samant, S.P. Harimkar, J.D. Majumdar, I. Manna, N.B. Dahotre, Surf. Coat. Technol. 202 (2008) 2623–2631. [4] M. Iqbal, J.I. Akhter, H.F. Zhang, Z.Q. Hu, J. Non-Cryst. Solids 354 (2008) 5363–5367. [5] S.H. Al-Heniti, J. Alloys Compd. 484 (2009) 177–184. [6] Y.C. Niu, X.F. Bian, W.M. Wang, S.F. Jin, X.J. Liu, J.Y. Zhang, G.L. Qin, J. Non-Cryst. Solids 351 (2005) 3854–3860. [7] I. Costa, M.C.L. Oliveira, H.G. de Melo, R.N. Faria, J. Magn. Magn. Mater. 278 (2004) 348–358. [8] E.J. Kelly, J. Electrochem. Soc. 124 (1977) 987–994. [9] A. Terlain, T. Dufrenoy, J. Nucl. Mater. 212 (1994) 1504–1508. [10] R. Sueptitz, K. Tschulik, M. Uhlemann, L. Schultz, A. Gebert, Electrochim. Acta 56 (2011) 5866–5871. [11] J. Hu, C.F. Dong, X.G. Li, K. Xiao, J. Mater. Sci. Technol. 26 (2010) 355–361. [12] A. Levesque, S. Chouchane, J. Douglade, R. Rehamnia, J.P. Chopart, Appl. Surf. Sci. 255 (2009) 8048–8053. [13] R. Peipmann, J. Thomas, A. Bund, Electrochim. Acta 52 (2007) 5808–5814. [14] A. Bund, A. Ispas, J. Electroanal. Chem. 575 (2005) 221–228. [15] G. Hinds, J. Coey, M. Lyons, Electrochem. Commun. 3 (2001) 215–218. [16] M. Waskaas, Y.I. Kharkats, J. Electroanal. Chem. 502 (2001) 51–57. [17] S. Legeai, M. Chatelut, O. Vittori, J.P. Chopart, O. Aaboubi, Electrochim. Acta 50 (2004) 51–57. [18] R. Sueptitz, K. Tschulik, M. Uhlemann, A. Gebert, L. Schultz, Electrochim. Acta 55 (2010) 5200–5203. [19] Z.P. Lu, D.L. Huang, W. Yang, J. Congleton, Corros. Sci. 45 (2003) 2233–2249. [20] C. Wang, S.H. Chen, H.Y. Ma, J. Electrochem. Soc. 145 (1998) 2214–2218. [21] S. Koehler, A. Bund, J. Phys. Chem. B 110 (2006) 1485–1489. [22] O. Devos, O. Aaboubi, J.P. Chopart, A. Olivier, C. Gabrielli, B. Tribollet, J. Phys. Chem. A 104 (2000) 1544–1548. [23] Z.P. Lu, W. Yang, Corros. Sci. 50 (2008) 510–522. [24] G. Hinds, F. Spada, J. Coey, T. Ní Mhíocháin, M. Lyons, J. Phys. Chem. B 105 (2001) 9487–9502. [25] M. Jamesh, S. Kumar, T.S.N. Sankara Narayanan, Corros. Sci. 53 (2011) 645–654. [26] C.L. Li, Y.T. Ma, Y. Li, F.H. Wang, Corros. Sci. 52 (2010) 3677–3686. [27] F. Rosalbino, E. Angelini, D. Macciò, A. Saccone, S. Delfino, Electrochim. Acta 54 (2009) 1204–1209. [28] F.F. Marzo, A.R. Pierna, J. Barranco, G. Vara, A. Perez, T. Gómez-Acebo, J. Non-Cryst. Solids 353 (2007) 875–878. [29] P. Hammer, M.G. Schiavetto, F.C. dos Santos, A.V. Benedetti, S.H. Pulcinelli, C.V. Santilli, J. Non-Cryst. Solids 356 (2010) 2606–2612. [30] F. Malekmohammadi, A. Sabour Rouhaghdam, T. Shahrabi, J. Non-Cryst. Solids 357 (2011) 1141–1146. [31] Y.L. Huang, H. Shih, H.C. Huang, J. Daugherty, S. Wu, S. Ramanathan, C. Chang, F. Mansfeld, Corros. Sci. 50 (2008) 3569–3575.

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