Sludge Reduction and Surface Investigation in Electrochemical Machining by Complexing and Reducing Agents

Electrochemical machining (ECM) is widely applied to manufacture parts with complex geometries, used in electronic components and the automotive, military, and aeronautics industries. These parts have a surface shaped by controlled anodic dissolution at high current density levels, using a neutral solution of inorganic salts (i.e., NaCl or NaNO3) as the electrolyte. Such conditions generate a high amount of sludge that deposits onto the surfaces of equipment, devices, cathodes, and working pieces, requiring daily and complicated sludge management during the series production in the industry. Thus, the main goal of the present work is to propose a simple way to reduce sludge generation in the ECM industrial process. To do so, complexing (EDTA) or reducing (ascorbic acid) agents were added to the electrolyte composition, creating parallel reactions to keep the metallic ions from precipitating. The complexing agent EDTA resulted in a 30% reduction in sludge mass, using an alkaline solution (pH > 10.0). The reducing agent, ascorbic acid, resulted in a 90% reduction in sludge mass, using an acidic solution (pH < 5.0). This sludge reduction has the potential to contribute significantly to increasing equipment, devices, and cathode lifetime, as well as reducing costs associated with centrifuge or filter maintenance (sludge removal from electrolyte) and increasing the productivity of industrial ECM processes.

Automated summary

Electrochemical machining (ECM) is widely used to manufacture parts with complex geometries. The generation of sludge during ECM process requires daily and complicated sludge management. This study proposes a simple method by adding complexing (EDTA) or reducing (ascorbic acid) agents to the electrolyte composition, resulting in a significant reduction in sludge mass. This sludge reduction has the potential to increase equipment lifetime and productivity, as well as reducing costs associated with sludge removal.