Effect of the breakdown time of a passive film on the electrochemical machining of rotating cylindrical electrode in NaNO3 solution

To illustrate the effect of the breakdown time of a passive film, ECM tests with cylindrical electrodes at different rotational speeds are conducted. The results indicate a correlation between the breakdown time and the rotational speed. At a high rotational speed, the surface of the anode workpiece is always in a passive state due to the existence of the breakdown time of a passive film, and hardly any material is removed. When a slower rotational speed is used, the steel passivity can be overcame, and a high material removal rate is obtained. A numerical simulation of the current density distribution on the cylindrical anode surface is performed, and the relationship between total metal dissolution time and breakdown time is found. It is seen that the breakdown time of the passive film can have a strong effect on the metal removal rate in ECM.