The electrochemical behaviour of metal particles in spouted, packed and fluidized bed electrodes can be visualized in the same way as in the electrochemical corrosion demonstration. The cathodic reaction, indicated by bright red colour (grey in black-white photographs), occurs on the particles in contact with the cathode current feeder. The profile of red colour corresponds to the current density distribution. This is relevant for all particles in the fixed packed bed and in the annulus of the spouted bed, and for those particles in the fluidized bed which are in contact with the cathode current feeder. All the particles in the spout and fountain of the spouted bed and the majority of the particles in the fluidized bed are not in contact wi th the cathode current feeder. They are characterized by bipolar behaviour because the resistance of the electrical transfer through the particle is less than that through the surrounding electrolyte. The anodic reaction, indicated by dark blue colour (black in black-white photographs), occurs on the part of the particles in the direction of the cathode current feeder, while the opposite side of the particles is under the cathodic reaction, visualized by bright red colour. The method described could be used for the optimization of three-dimensional electrodes.