Magnetic Field Effects on Electrochemical Reactions Occurring at Metal/Flowing‐Electrolyte Interfaces

Abstract

A study was made to determine whether a magnetic field, such as that associated with a thermonuclear reactor, might adversely affect the corrosion behavior of metallic surfaces in contact with a flowing electrolyte. In metal/ flowing‐electrolyte systems, electrochemical reactions dependent on the metal/ electrolyte interfacial potential difference are affected by an applied magnetic field as a consequence of the Lorentz forces acting on the charged components of the flowing electrolyte. A theoretical analysis of the magnetic field effect was developed, and its validity established by experiments involving the normalTi/H2SO4 false(H2‐normalsaturatedfalse) system. Quantitative agreement between theoretical and experimental results was obtained for the electrochemical behavior of Ti in 1N H2SO4 (mean flow velocity: 0–650 cm/sec) over the available range of magnetic flux density (0–2.1 Tesla). Although the experimental work employed discrete Ti electrodes set in the wall of nonconducting Pyrex glass pipe, the theory was extended to include metallic pipes, i.e., the “conducting‐wall” case, for which case the “wall‐shorting” effect was shown to be negligible. In addition to the adverse effect of a magnetic field on the “uniform” corrosion behavior of metals, the imposition of a magnetic field can also result in enhanced susceptibility to stress corrosion cracking, localized (pitting or crevice) corrosion, oxidation and reduction of solution species, and electrochemical decomposition of the electrolyte. The aforementioned processes, to name a few, are all potential dependent and, consequently, subject to the magnetic field effect.

Applications of magnetoelectrolysis

“…Kinetic effects can be modelled by defining a magnetically induced potential difference [27][28][29]. Kelly [28] uses ButlerVolmer kinetics to describe this, and has analysed the total anodic and cathodic polarization in a cell consisting of two titanium electrodes in a flowing H2SO4-electrolyte. The effect of the induced potential difference on current density can be written as (for a purely activation controlled reduction reaction):…”

“…Under carefully chosen conditions the following effects can be promoted: (i) a more uniform deposit morphology (microscopic as well as macroscopic) [27,31,33,39,[40][41][42][43], (ii) inhibition of dendrite growth [37,44], (iii) change in macrostress of the deposit [45], (iv) increased hardness of the deposit [29,41,46], (v) a more uniform current distribution [47,48], (vi) increased corrosion resistance [28,29] and (vii) composition shift in alloy plating [46].…”

Investigation of corrosion defects in titanium by positron annihilation

“…One aspect of corrosion that is not fully explained before is the effect of a magnetic fi eld on the kinetics of this process [5][6][7]. Researchers have found, among other things, that the magnetic fi eld strongly infl uences the kinetics of the formation of corrosion pits in ferromagnetic materials but have no contribution to the corrosion in austenitic steel grades.…”

The Influence of a Magnetic Field on the Formation of Corrosion Defects in Selected Metals and Steels, Analysed Using Positron Annihilation Method

“…In some metals (e.g., iron and copper), a magnetic eld inhibits corrosion in some conditions, but in other metals (Ti), the eld accelerates it. Kelly [11] found that an external magnetic eld accelerates corrosion processes in ferromagnetic iron and steel, but has no visible impact on corrosion in austenitic steel. Linhardt and co-workers [12] demonstrated that as long as the metal is passive, the magnetic eld has no impact on the kinetics of corrosion pit formation in AISI 304 austenitic steel.…”