The electrochemical oxidation of hydrogen was investigated potentio statically at 30 °C and atmospheric pressure using two movable flat‐plate platinum anodes which were partially immersed in . The importance of meniscus formation, electrolyte film formed on the exposed portion of the anode, surface roughness, and hydrogen adsorption on the exposed portion of the anode is demonstrated by transient currents resulting from vertical movements of the anodes. The two anodes of different surface roughnesses, one surface altered by sandblasting and the other by platinizing, were tested at the following conditions: (a) stationary positions, (b) lowering and raising at constant rates (0.7 to 23.8 cm/min), and (c) sudden lowering and raising (greater than 480 cm/min). Surface roughness was a determining factor in the evaluation of the data. The roughness of both anodes was temporarily changed by an electrochemical oxidation‐reduction technique. The results of the investigation lend support to the thin film model for porous gas diffusion electrodes.