Abstract The effects of a magnetic field on electrolytic currents in hexacyanoferrate(II) and hexacyanoferrate(III) solutions were studied under various conditions by means of potentiometry. These effects were observed for a wide range of current densities (10−6–10−3 A/cm2). The results were interpreted in terms of the magnetohydrodynamic effect, including a change in the solution density during electrolysis. The present observation suggests that a magnetohydrodynamic flow strongly affects the electrochemical processes on an electrode surface.