Surface Finish in ECM

Surface finish in ECM is affected by the following factors:

• Unevenness of surface finishes due to change in potential difference.
• Sporadic breakdown of anodic film.
• Eddies formation and flow separation.
• Generation of H₂ gas at cathode.

Unevenness of surface occurs due to potential gradient across the gap and potential difference inside the grain of different alloying element in the work material. If the potential gradient across the gap is higher unevenness of surface finish will be less and vice versa. Sporadic breakdown occurs due to gradual fall in potential difference between the anode and cathode away from the machining area and results in poor surface finish.

The presence of rough surface, i.e., hills and valleys on anode surface leads to the separation of electrolyte flow and eddy formation. Due to eddy formation there may be ion concentration and overpotential on eddies. This causes variation in metal removal rate and produces uneven surface.

During electrolysis H₂ gas is produced at cathode. H₂ gas reduces the specific conductivity of electrolyte and causes the deterioration of the surface finish.