Non-monotonic influence of a magnetic field on the electrochemical behavior of Fe78Si9B13 glassy alloy in NaOH and NaCl solutions

International Journal of Minerals, Metallurgy and Materials, Oct 2014

The corrosion behavior and microstructure of Fe78Si9B13 glassy alloy in NaOH and NaCl solutions under a 0.02-T magnetic field were investigated through electrochemical testing and scanning electron microscopy (SEM). The current-density prepeak (PP) in the anodic polarization curves in low-concentration NaOH solutions (classified as type I) tends to disappear when the NaOH concentration is increased to 0.4 mol/L and the magnetic field is applied. Under the magnetic field, the height of the second current-density peak is increased in low-concentration NaOH solutions (type I) but decreased in high-concentration NaOH solutions (type II). The non-monotonic effect of the magnetic field was similarly observed in the case of polarization curves of samples measured in NaCl solutions. Ring-like corroded patterns and round pits are easily formed under the magnetic field in NaOH and NaCl solutions. These experimental results were discussed in terms of the magnetohydrodynamic (MHD) effect.

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Non-monotonic influence of a magnetic field on the electrochemical behavior of Fe78Si9B13 glassy alloy in NaOH and NaCl solutions

Hong-di Zhang Xiao-yu Li Jing Pang Li-juan Yin Hai-jian Ma Ying-jie Li Yan Liu Wei-min Wang The corrosion behavior and microstructure of Fe78Si9B13 glassy alloy in NaOH and NaCl solutions under a 0.02-T magnetic field were investigated through electrochemical testing and scanning electron microscopy (SEM). The current-density prepeak (PP) in the anodic polarization curves in low-concentration NaOH solutions (classified as type I) tends to disappear when the NaOH concentration is increased to 0.4 mol/L and the magnetic field is applied. Under the magnetic field, the height of the second current-density peak is increased in low-concentration NaOH solutions (type I) but decreased in high-concentration NaOH solutions (type II). The non-monotonic effect of the magnetic field was similarly observed in the case of polarization curves of samples measured in NaCl solutions. Ring-like corroded patterns and round pits are easily formed under the magnetic field in NaOH and NaCl solutions. These experimental results were discussed in terms of the magnetohydrodynamic (MHD) effect. Corresponding author: Wei-min Wang E-mail: University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg 2014 1) Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan 250061, China 2) Qingdao Yunlu Energy Technology Co. Ltd., Qingdao 266109, China 3) School of Mechanical and Electrical Engineering, Weifang University, Weifang 261061, China (Received: 12 March 2014; revised: 21 April 2014; accepted: 24 April 2014) 1. Introduction Fe-based amorphous alloys, because of their special microstructure, exhibit interesting characteristics, such as excellent soft magnetic properties, high strength, and improved resistance to corrosion, which differ from the properties of their corresponding crystalline alloys [15]. In particular, Fe78Si9B13 glassy alloy has been widely used in power transformers and electronic devices, which are always under the influence of a magnetic field. Many power transformers are installed outdoors and utilized for more than twenty years. Hence, the corrosion resistance of Fe78Si9B13 glassy alloy under a magnetic field is a worthwhile topic of study. Numerous investigations have revealed that the introduction of a magnetic field affects the corrosion behavior of Fe-based glassy alloys, and the literature contains some controversial views on this topic [6]. Electrochemical testing has been used to investigate the effect of magnetic fields on the corrosion properties of amorphous alloys, and the anodic polarization of these alloys can be divided into several stages, such as anodic dissolution, a mass transport range, and a passive range [7]. The mass transport rates of electrochemical reactions have been observed to closely depend on the magnetic field, which can be analyzed on the basis of the magnetohydrodynamic (MHD) theory [8]. Digital holography technology is also used in the investigation of the magnetic field effect of corrosion behavior in different solutions [913]. In recent years, the electrochemical behavior of iron in acidic solutions, alkali solutions, and aqueous solutions under a magnetic field with a fixed flux density or different flux densities has been widely discussed [1417]. The theoretical implications and potential practical applications of the applied magnetic field to govern electrochemical behavior have been used in industry, such as to enhance mass transfer, improve electrodeposition quality, and control potential distribution and current [1821]. However, to our knowledge, the literature contains few reports on the corrosion behavior of Fe-based glassy alloys in NaOH solutions with different concentrations or in the solutions with chloride ions under a magnetic field. Electrochemical investigations of Fe-based amorphous alloys in different environments are helpful in widening their potential applications in industry. The aim of this study was to characterize the influence of a superimposed magnetic field on the corrosion behavior of Fe78Si9B13 glassy alloy in different NaOH and NaCl solutions. Furthermore, the corroded surfaces of the glassy alloy were investigated after the application of a magnetic field. The experimental results were discussed in terms of the MHD effects. 2. Experimental Glassy Fe78Si9B13 ribbons were supplied by the National Amorphous Nanocrystalline Alloy Engineering Research Center of China. Evaluations of corrosion resistance were performed by electrochemical testing in a typical three-electrode system, consisting of a working electrode (a stationary specimen, labeled as WE), a platinum counter electrode (CE), and a reference electrode (RE). As evident from the schematic diagram in Fig. 1, the magnetic field was introduced via two ferrite magnets with the same size. The electrolytic cell was centered between the magnets, and the magnetic field intensity was 0.02 T. The (...truncated)


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Hong-di Zhang, Xiao-yu Li, Jing Pang. Non-monotonic influence of a magnetic field on the electrochemical behavior of Fe78Si9B13 glassy alloy in NaOH and NaCl solutions, International Journal of Minerals, Metallurgy and Materials, 2014, pp. 1009-1018, Volume 21, Issue 10, DOI: 10.1007/s12613-014-1002-x