The electrochemical corrosion behavior of novel Cu-containing antibacterial austenitic and ferritic stainless steels in 0.05 mol/L NaCl solution has been investigated by dc polarization and ac impedance measurements and compared with that of the conventional stainless steels. Cu was found to particularly affect the kinetics of the anodic reaction. The corrosion performance of the austenite was greatly improved by Cu addition in the studied anodic potential range, whereas Cu effects on the ferrite showed remarkable sensitivity to the applied potential and improved corrosion resistance only in the low anodic potential range. Three-dimensional presentation of the variable-potential impedance data was employed in analyzing the electrochemical corrosion processes and revealed a close relationship between the impedance parameters and the applied potential. The trends of impedance results agree well with those obtained from potentiodynamic polarization measurements.