Dissolution Characteristics of Iron and Stainless Steels in Chloride under Electrochemical Machining Conditions

Abstract

Ultrasound has been used to produce time-resolved gap data during electrochemical machining (ECM), enabling calculation of the time-dependent dissolution valency and surface overpotential as a function of ECM dissolution current . Measurement of the - dissolution characteristics of iron and the stainless-steels Jethete (J) and SS410 in chloride electrolyte under the relatively high workpiece feed, high current density, high electrolyte flow conditions applicable to industrial ECM has shown that, in each case, the ECM voltage is initially predominantly applied across the workpiece surface, consistent with the presence of a passivating surface oxide film. This voltage then falls, consistent with a marked reduction in passivation. Reproducible, near-ohmic - behavior is then observed, independent of applied ECM voltage, initial gap, feed, and electrolyte concentration, suggesting that the fundamental - dissolution characteristics of the workpieces are being measured. For Fe, J, and SS410, relatively low values are observed, consistent with active dissolution along with mean near-ohmic resistances of , consistent with the presence of a resistive metal salt film on the workpiece surface. As well as giving insight into the dissolution process occurring under ECM conditions, these data provide a parameter base for the accurate modeling of the ECM process.