The variation of the cathode polarization potential with time during electrolysis at various current densities, and with cathode bases of different structures, has been studied. The effects of cold‐rolled and annealed foil cathodes, showing preferred orientation and random orientation, respectively, have been compared, and measurements have also been made using electrodeposited “constant state polarization” bases produced under standard conditions, and electrodeposited bases of coarse and fine structure. The deposits formed under some of these conditions have been examined by x‐ray methods. The results support the view of Blum and Rawdon that the cathode polarization is related to crystal size and a change from a coarse to a fine structure is accompanied by un increase in polarization potential.