Metal substitution reaction between solid metal and ionic solution occurs according to ionization tendency. In these reactions, the micro MHD effect and magnetic convection can affect the reaction rate under imposition of an intense magnetic field.
In this study, the effects of a magnetic field up to 5 T and its gradient on the metal substitution reaction of copper(II) sulfate solution with solid iron or solid zinc were investigated. Both the micro MHD effect and magnetic convection can affect the reaction rate. The micro MHD effect, which promotes the metal substitution reaction, appears more strongly for zinc than for iron, because the ionization tendency of zinc is higher than that of iron. Magnetic convection can promote or suppress the natural convection around the metal surface in the solution. For the system of solid iron in the solution, natural convection, which is induced by the buoyancy of iron-rich solution around the solid iron, is suppressed by downward magnetic convection, because iron ions are paramagnetic, and is promoted by upward magnetic convection. In contrast, zinc ions are diamagnetic, and the effect of magnetic convection around solid zinc is opposite the effect around solid iron.