Abstract
The anodic behavior of copper has been studied in connection with the elucidation of the mechanism of its electropolishing in orthophosphoric acide media. The horizontal section of the current-potential curve, which was considered by Jacquet as being uniform, has been investigated in greater detail by means of the potentiostatic method with a copper rod electrode in quiet media and with a rotated copper wire electrode.
Extrapolation to zero current of the plot of current at zero time against potential indicates that the initial step of the electrode reaction occurring in the entire potential range corresponding to the horizontal part of the current-potential curve is represented by
2Cu+H2O→Cu2O+2H++2e.
The initial current is controlled by the charge transfer process of the above reaction, while the steady-state current is controlled by the mass transfer process involved in the dissolution process of the cuprous oxide.
Depending on the shape of current-time curves, the horizontal part of the current-potential curve may be divided into three ranges; i. e. high, intermediate, and low potential ranges. The mode of transition of current-controlling process from the charge transfer to the mass transfer process is different in different potential regions.
