A simple method for measuring the self‐generated corrosion current has been devised for aluminum specimens. Correlation between loss in weight calculated from current‐time curves and measured loss in weight indicates that the corrosion of aluminum in neutral alkali chloride solutions is largely or entirely electrochemical in nature. Current measurements indicate that as the number of sites of attack increases, the intensity of attack decreases, as was shown by another method in previous work. By consideration of the anodic and cathodic polarization characteristics of aluminum, the potential and distribution of current in the corrosion cell can be explained quantitatively on an electrochemical basis. It is established that, in the case of aluminum at least, measurement of the single potential probably can be used to detect the occurrence of film failure but should not be used indiscriminately to measure the extent of film failure or the intensity of attack. The effect of external and internal resistance on the potential and current characteristics of corrosion cells has been measured and a zero‐resistance method of measuring short circuit current has been applied.