ECM Behavior of Steel in NaClO4 Electrolytes

Abstract

Since there is some degradation of NaClO3 electrolytes during the ECM operation, it was thought that the more stable ClO4 ion could provide a longer-lived ECM electrolyte. To test this suggestion, steady-state potentiostatic polarization curves were obtained on mild steel anodes and the amount of oxide on the steel anode surface was determined at each point on the polarization curve from galvanostatic stripping curves. From the results of these studies, the ECM behavior of steel in NaClO4 solutions was predicted and then compared to the actual ECM of steel specimens in laboratory test rigs. The correlation between the basic and operational studies is good. It is concluded that an oxide film must be present to provide good dimensional control and machining geometry but the quality of the surface finish is determined by the type of film formed (must be uniform, thin and porous to get electropolishing of the metal surface).