A combination of thermodynamic analyses and potentiodynamic polarization tests have been used to study the anodic behavior of Cu in strong H2SO4 solutions in the concentration range 1-10 M. The studies were supplemented by chemical analyses of surface films. It was found that concentration-dependent changes in the activity of water played a major role in determining the anodic behavior and relative stability of corrosion product films. The anodic Tafel slope decreased from similar to 41 to similar to 31 mV with increasing acid concentration. The onset of limiting current and active-passive behaviors at higher potentials was determined by the formation of films of hydrated copper sulfate, CuSO4 . xH(2)O, and not by formation of oxides. Limiting current behavior was observed in 1 M solutions, where the degree of hydration was x = 5. Well-developed passivity occurred in 10 M solutions where x = 1. The results are relevant to industrial electrorefining operations for Cu and indicate that chloride contamination, if present in sufficient amounts, could cause the premature onset of limiting current behavior (anode "passivity") during refining.