Formation and Breakdown of Oxide Films in High-Rate Anodic Dissolution of Chromium–Nickel Steels in Electrolytes for Electrochemical Machining

It is shown that, in high-rate pulsed galvanostatic anodic dissolution of type CSN17335 and AISI 304 chromium–nickel steels electrolytes for electrochemical machining (ECM) (chloride, nitrate, mixed chloride–nitrate solutions with a conductivity 0.15 S/cm) using microsecond pulses duration 20–2000 ?s current densities the range 1–100 A/cm2, substantial fraction charge (up to ~40%) spent on formation passivating oxide film semiconducting behavior. The treatment therefore directly involves film, not alloy. As consequence, efficiency ECM these materials ~60–70%, depending alloy composition. When direct current, rate increases as result breakdown due its thermokinetic instability (“thermal explosion”) caused by rise surface temperature.