Normally, magnetoconvection driven by the Lorentz force increases the limiting current in the mass-transport limited regime, roughly as the one-third power of the applied magnetic field. Here we show that an applied field can actually diminish the rate of copper electrode position at low overpotentials. The effect is related to the formation of a vortex at the leading edge of the flow. Similar, but weaker effects are due to gravity. (C) 2008 Elsevier B.V. All rights reserved.