Dass Amala, Counsil Joseph A, Gao Xuerong, Leventis Nicholas
Department of Chemistry, University of Missouri-Rolla, Rolla, Missouri 65409, USA.
J Phys Chem B. 2005 Jun 2;109(21):11065-73. doi: 10.1021/jp0442495.
Magnetic fields shift the open circuit potential (OCP) of ferromagnetic electrodes (Fe, Co, and Ni) in corroding solutions. The OCP changes we observe (a) follow the series Fe>Co>Ni; (b) increase with the magnetic flux density; (c) reach a maximum with disk electrodes approximately 1 mm in diameter; and (d) depend on the orientation of the electrode. We report that when the surface of the electrode is oriented parallel (theta = 90 degrees) or perpendicular (theta = 0 degrees) to the magnetic field, the open circuit potential moves in opposite directions (positive and negative, respectively) with the largest changes occurring when the electrode surface is parallel to the magnetic field. Nonconvective sleeve electrodes produce the same behavior. The overall experimental evidence suggests that the magnetic field changes the OCP by modifying the surface concentrations of the paramagnetic participants in the corrosion process of the ferromagnetic electrode by species in solution; this in turn is accomplished by imposing a field-gradient driven mode of mass transfer upon paramagnetic species in solution (magnetophoresis). Simulations of the magnetic field around the ferromagnetic electrode at the two extreme orientations considered here show that in one case (theta = 90 degrees) field gradients actually repel, while in the other case (theta = 0 degrees) they attract paramagnetic species in the vicinity of the electrode.
磁场会改变铁磁电极（铁、钴和镍）在腐蚀溶液中的开路电位（OCP）。我们观察到的开路电位变化：（a）遵循Fe>Co>Ni的顺序；（b）随磁通密度增加；（c）对于直径约1毫米的圆盘电极达到最大值；（d）取决于电极的取向。我们报告，当电极表面与磁场平行（θ = 90度）或垂直（θ = 0度）时，开路电位会向相反方向移动（分别为正向和负向），当电极表面与磁场平行时变化最大。非对流套筒电极也表现出相同的行为。总体实验证据表明，磁场通过改变溶液中物种在铁磁电极腐蚀过程中顺磁参与者的表面浓度来改变开路电位；这反过来是通过对溶液中的顺磁物种施加场梯度驱动的传质模式（磁泳）来实现的。在此考虑的两个极端取向的铁磁电极周围磁场的模拟表明，在一种情况下（θ = 90度）场梯度实际上是排斥的，而在另一种情况下（θ = 0度）它们吸引电极附近的顺磁物种。
