The anodic polarization characteristics of copper have been studied under a variety of environmental conditions. In dilute acid solutions at room temperature, copper may dissolve at rates limited by a diffusion‐controlled current; increasing the acid concentration results in an increased tendency for passivation. Lowering the temperature promotes the establishment of passivity. A passivation reaction was observed in all the alkaline solutions studied. Galvanostatic charging and decay curves show the existence of several potential plateaus which have been correlated with probable potential‐dependent surface reactions.