Challenges and control strategies for disrupting passive oxide layer formation in electrochemical machining

Electrochemical machining (ECM) is a non-traditional, precision machining process involving the removal of material through anodic dissolution. It is commonly utilized for machining complex geometries in conductive materials, especially in aerospace, biomedical, and automotive sectors. While having numerous benefits, ECM also has a major challenge: the development of a passive oxide layer on the surface of the workpiece. The formation of this layer depends on various factors, such as workpiece material, electrolyte composition, current density, and machining conditions. If not properly controlled, it can cause poor surface finish, dimensional errors, and increased energy consumption. To counter this problem, several control strategies have been devised that play a crucial role in breaking down the passive film. This review critically analyses and compares these strategies for inhibiting passive layer growth in ECM. It highlights both traditional and established techniques as well as novel developments like hybrid ECM methods, AI-driven process optimization, and real-time monitoring systems. The review aims to provide a material-specific and application-oriented perspective, highlighting the advantages, limitations, and technical viability of each strategy. By integrating findings from experimental studies, simulation work, and emerging technologies, this review provides a comprehensive resource for researchers and practitioners seeking to enhance the reliability, performance, and precision of ECM processes in high-tech manufacturing.