Reduction of stray corrosion in electrochemical discharge drilling by changing the electric field distribution

Abstract

Electrochemical discharge drilling is an effective way to machine micro-hole without recast layer. During this process, stray corrosion caused by stray current will damage the surface quality around the entrance of micro-holes. Insulation coating and auxiliary anode, which can change the electric field, have been applied to reduce stray corrosion. As shown in the simulation, if non-machined zone of the workpiece is insulated, stray current will concentrate around the entrance of the micro-hole and high current density will reduce intergranular and secondary corrosion. Apart from that, using auxiliary anode whose voltage is higher than the workpiece can not only change the direction of the current flow, but also decrease the current density and stray corrosion in non-machined zone of the workpiece. Furthermore, the dimension of the auxiliary anode and the gap width between workpiece and auxiliary anode determine the effect of the auxiliary anode. Experiments prove that the use of auxiliary anode and insulation coating can change the distribution of electric field, eliminate the stray corrosion caused by stray current, and improve the surface quality of the workpiece.