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)