Temperature distribution along the gap in electrochemical machining

The temperature of the flowing electrolyte solution within the inter-electrode gap has been measured by means of miniature bead-thermistors. For NaCl solution the temperatures recorded within the gap are higher than those outwith the gap. As the flow-rate is reduced the temperature within the gap increases to a maximum which corresponds closely to the boiling state of the electrolyte. These results are consistent with measurements in a region of increased resistivity within the gap such as that provided by the hydrogen bubble-electrolyte layer adjacent to the cathode. Similar tests with NaNO3 solution have shown that the temperatures within the gap are much lower with that electrolyte than with NaCl solution. These effects follow previous observations that substantially less hydrogen gas is evolved with NaNO3 than with the NaCl electrolyte.