Analysis of Reactions Determining Current Efficiency in Electrochemical Machining

In electrochemical machining (ECM), it is widely accepted that the current efficiency of NaCl is 100% and is independent of pulse duration. Moreover, it is also known that the current efficiency of NaNO3 is not 100%. It was found in the experiments that the current efficiency using both the electrolytes depended upon the pulse duration and in case of NaCl, it reduced as the pulse duration was shortened. In this study, the reason for the above behaviour of the electrolytes is investigated. For that, transparent electrodes like semi-conductor Ga2O3 wafer were utilized to observe the inter-electrode gap phenomenon while machining. The gas generated was also collected and analysed by gas chromatography to know the reactions occurring in the gap. Finally, simulation was performed considering ion transport equations and reactions to verify the theory. The suppression of oxygen generation on anode as the pulse duration was increased was found to be the main reason why the current efficiency increased with the pulse duration.